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Sample records for acid catalyzed esterification

  1. Boric acid catalyzed chemoselective esterification of alpha-hydroxycarboxylic acids.

    PubMed

    Houston, Todd A; Wilkinson, Brendan L; Blanchfield, Joanne T

    2004-03-01

    Boric acid catalyzes the selective esterification of alpha-hydroxycarboxylic acids without causing significant esterification to occur with other carboxylic acids. The procedure is simple, high-yielding, and applicable to the esterification of alpha-hydroxy carboxylates in the presence of other carboxylic acids including beta-hydroxyacids within the same molecule. [reaction: see text

  2. Kinetic study of free fatty acid esterification reaction catalyzed by recoverable and reusable hydrochloric acid.

    PubMed

    Su, Chia-Hung

    2013-02-01

    The catalytic performance and recoverability of several homogeneous acid catalysts (hydrochloric, sulfuric, and nitric acids) for the esterification of enzyme-hydrolyzed free fatty acid (FFA) and methanol were studied. Although all tested catalysts drove the reaction to a high yield, hydrochloric acid was the only catalyst that could be considerably recovered and reused. The kinetics of the esterification reaction catalyzed by hydrochloric acid was investigated under varying catalyst loading (0.1-1M), reaction temperature (303-343K), and methanol/FFA molar ratio (1:1-20:1). In addition, a pseudo-homogeneous kinetic model incorporating the above factors was developed. A good agreement (r(2)=0.98) between the experimental and calculated data was obtained, thus proving the reliability of the model. Furthermore, the reusability of hydrochloric acid in FFA esterification can be predicted by the developed model. The recoverable hydrochloric acid achieved high yields of FFA esterification within five times of reuse.

  3. Iodine-Catalyzed Polysaccharide Esterification

    Technology Transfer Automated Retrieval System (TEKTRAN)

    A review is provided of the recent reports to use iodine-catalyzed esterification reaction to produce esters from polysaccharides. The process entails reaction of the polysaccharide with an acid anhydride in the presence of a catalytic level of iodine, and in the absence of additional solvents. T...

  4. Vapor-phase esterification of acetic acid with ethanol catalyzed by a macroporous sulfonated styrene-divinylbenzene (20%) resin

    SciTech Connect

    Gimenez, J.; Costa, J.; Cervera, S.

    1987-02-01

    The kinetics of the vapor-phase (85-120/sup 0/C) esterification of acetic acid with ethyl alcohol, at atmospheric pressure, catalyzed by a macroporous sulfonated styrene-divinylbenzene (DVB;20%) resin, has been studied. A simple first-order model (r = kp/sub 1/) fits experimental kinetic data properly for a constant reactants ratio. Discussion by means of L-H-H-W models shows that the rate-controlling step is the surface reaction with a single-site mechanism. The apparent activation energy is 4000 cal/mol.

  5. Microswelling-free negative resists for ArF excimer laser lithography utilizing acid-catalyzed intramolecular esterification

    NASA Astrophysics Data System (ADS)

    Hattori, Takashi; Tsuchiya, Yuko; Yokoyama, Yoshiyuki; Oizumi, Hiroaki; Morisawa, Taku; Yamaguchi, Atsuko; Shiraishi, Hiroshi

    1999-06-01

    We have examined alicyclic polymers with a (gamma) -hydroxy acid structure in order to investigate the properties of (gamma) -hydroxy acid and (gamma) -lactone as function groups of ArF negative resist materials. From the viewpoint of transparency and dry-etching resistance, (gamma) -hydroxy acid and (gamma) -lactone structure were found to be suitable for ArF negative resists materials. Surprisingly, the reactivity of the acid-catalyzed reaction of (gamma) -hydroxy acid is affected by the polymer structure. Using ArF excimer laser stepper, 0.20-micrometers line-and-space patterns without micro-swelling distortion were obtained from a negative resist consisting of alicyclic polymer with the (gamma) - hydroxy acid structure and a photoacid generator. Distortion was avoided because the number of carboxyl groups decreased drastically in the exposed area by the acid-catalyzed intramolecular esterification of (gamma) -hydroxy acid to (gamma) -lactone. As a result, (gamma) -hydroxy acid and (gamma) -lactone structure were found to be suitable function groups for ArF negative resist materials.

  6. Acetylation of bacterial cellulose catalyzed by citric acid: Use of reaction conditions for tailoring the esterification extent.

    PubMed

    Ávila Ramírez, Jhon Alejandro; Gómez Hoyos, Catalina; Arroyo, Silvana; Cerrutti, Patricia; Foresti, María Laura

    2016-11-20

    Bacterial cellulose (BC) nanoribbons were partially acetylated by a simple direct solvent-free route catalyzed by citric acid. The assay of reaction conditions within chosen intervals (i.e. esterification time (0.5-7h), catalyst content (0.08-1.01mmol/mmol AGU), and temperature (90-140°C)), illustrated the flexibility of the methodology proposed, with reaction variables which can be conveniently manipulated to acetylate BC to the required degree of substitution (DS) within the 0.20-0.73 interval. Within this DS interval, characterization results indicated a surface-only process in which acetylated bacterial cellulose with tunable DS, preserved fibrous structure and increased hydrophobicity could be easily obtained. The feasibility of reusing the catalyst/excess acylant in view of potential scale-up was also illustrated.

  7. Acetylation of bacterial cellulose catalyzed by citric acid: Use of reaction conditions for tailoring the esterification extent.

    PubMed

    Ávila Ramírez, Jhon Alejandro; Gómez Hoyos, Catalina; Arroyo, Silvana; Cerrutti, Patricia; Foresti, María Laura

    2016-11-20

    Bacterial cellulose (BC) nanoribbons were partially acetylated by a simple direct solvent-free route catalyzed by citric acid. The assay of reaction conditions within chosen intervals (i.e. esterification time (0.5-7h), catalyst content (0.08-1.01mmol/mmol AGU), and temperature (90-140°C)), illustrated the flexibility of the methodology proposed, with reaction variables which can be conveniently manipulated to acetylate BC to the required degree of substitution (DS) within the 0.20-0.73 interval. Within this DS interval, characterization results indicated a surface-only process in which acetylated bacterial cellulose with tunable DS, preserved fibrous structure and increased hydrophobicity could be easily obtained. The feasibility of reusing the catalyst/excess acylant in view of potential scale-up was also illustrated. PMID:27561540

  8. Selective heterogeneous acid catalyzed esterification of N-terminal sulfyhdryl fatty acids

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Our interest in thiol fatty acids lies in their antioxidative, free radical scavenging, and metal ion scavenging capabilities as applied to cosmeceutical and skin care formulations. The retail market is filled with products containing the disulfide-containing free fatty acid, lipoic acid. These pr...

  9. Effect of polyvinylpyrrolidone on mesoporous silica morphology and esterification of lauric acid with 1-butanol catalyzed by immobilized enzyme

    SciTech Connect

    Zhang, Jinyu; Zhou, Guowei Jiang, Bin; Zhao, Minnan; Zhang, Yan

    2014-05-01

    Mesoporous silica materials with a range of morphology evolution, i.e., from curved rod-shaped mesoporous silica to straight rod-shaped mesoporous silica, were successfully prepared using polyvinylpyrrolidone (PVP) and triblock copolymer as dual template. The effects of PVP molecular weight and concentration on mesoporous silica structure parameters were studied. Results showed that surface area and pore volume continuously decreased with increased PVP molecular weight. Mesoporous silica prepared with PVP K30 also possessed larger pore diameter, interplanar spacing (d{sub 100}), and cell parameter (a{sub 0}) than that prepared with PVP K15 and PVP K90. In addition, with increased PVP concentration, d{sub 100} and a{sub 0} continuously decreased. The mechanism of morphology evolution caused by the change in PVP concentration was investigated. The conversion rate of lauric acid with 1-butanol catalyzed by immobilized Porcine pancreatic lipase (PPL) was also evaluated. Results showed that PPL immobilized on amino-functionalized straight rod-shaped mesoporous silica maintained 50% of its esterification conversion rate even after five cycles of use with a maximum conversion rate was about 90.15%. - Graphical abstract: Curved rod-shaped mesoporous silica can be obtained at low and the highest PVP concentration, while straight rod-shaped mesoporous silica can be obtained at higher PVP concentration. - Highlights: • Mesoporous silica with morphology evolution from CRMS to SRMS were prepared. • Effects of PVP molecular weight and concentration on silica morphology were studied. • A possible mechanism for the formation of morphology evolution SiO{sub 2} was proposed. • Esterification of lauric acid with 1-butanol catalyzed by immobilized PPL.

  10. Lewis acid-catalyzed in situ transesterification/esterification of microalgae in supercritical ethanol.

    PubMed

    Jin, Binbin; Duan, Peigao; Xu, Yuping; Wang, Bing; Wang, Feng; Zhang, Lei

    2014-06-01

    The activities of several Lewis acid catalysts such SnCl2, FeCl3, ZnCl2, AlCl3, and NbCl5 for the in situ transesterification/esterification of lipid contained within a microalga (Chlorella pyrenoidosa) in ethanol at 350°C were examined to identify the most suitable catalyst in term of crude biodiesel (CBD) yield. Of those catalysts tested, ZnCl2 showed the highest performance toward the CBD production. Using ZnCl2 as catalyst, effects of reaction temperature (200-370 °C), time (0-120 min), ethanol to microalga ratio (EtOH:MA) (5/5-40/5), catalyst loading (0-30 wt.%), and algae moisture (0-80 wt.%) on the yields of product fractions and the properties of CBD were studied. The presence of ZnCl2 not only promoted the production of CBD but also showed activities toward the deoxygenation and denitrogenation of CBD. The moisture content in the starting material is the most influential factor affecting the yield and properties of CBD.

  11. Lewis acid-catalyzed in situ transesterification/esterification of microalgae in supercritical ethanol.

    PubMed

    Jin, Binbin; Duan, Peigao; Xu, Yuping; Wang, Bing; Wang, Feng; Zhang, Lei

    2014-06-01

    The activities of several Lewis acid catalysts such SnCl2, FeCl3, ZnCl2, AlCl3, and NbCl5 for the in situ transesterification/esterification of lipid contained within a microalga (Chlorella pyrenoidosa) in ethanol at 350°C were examined to identify the most suitable catalyst in term of crude biodiesel (CBD) yield. Of those catalysts tested, ZnCl2 showed the highest performance toward the CBD production. Using ZnCl2 as catalyst, effects of reaction temperature (200-370 °C), time (0-120 min), ethanol to microalga ratio (EtOH:MA) (5/5-40/5), catalyst loading (0-30 wt.%), and algae moisture (0-80 wt.%) on the yields of product fractions and the properties of CBD were studied. The presence of ZnCl2 not only promoted the production of CBD but also showed activities toward the deoxygenation and denitrogenation of CBD. The moisture content in the starting material is the most influential factor affecting the yield and properties of CBD. PMID:24768889

  12. Enzymatic gallic acid esterification.

    PubMed

    Weetal, H H

    1985-02-01

    Gallic acid esters of n-propyl and amyl alcohols have been produced by enzymatic synthesis in organic solvents using immobilized tannase. Studies indicate that maximum esterification of gallic acid occurs with amyl alcohol. The enzyme shows broad alcohol specificity. However, the enzyme exhibits absolute specificity for the acid portion of the ester. Studies were carried out on K(m), V(max), pH, and temperature optima.

  13. Effect of polyvinylpyrrolidone on mesoporous silica morphology and esterification of lauric acid with 1-butanol catalyzed by immobilized enzyme

    NASA Astrophysics Data System (ADS)

    Zhang, Jinyu; Zhou, Guowei; Jiang, Bin; Zhao, Minnan; Zhang, Yan

    2014-05-01

    Mesoporous silica materials with a range of morphology evolution, i.e., from curved rod-shaped mesoporous silica to straight rod-shaped mesoporous silica, were successfully prepared using polyvinylpyrrolidone (PVP) and triblock copolymer as dual template. The effects of PVP molecular weight and concentration on mesoporous silica structure parameters were studied. Results showed that surface area and pore volume continuously decreased with increased PVP molecular weight. Mesoporous silica prepared with PVP K30 also possessed larger pore diameter, interplanar spacing (d100), and cell parameter (a0) than that prepared with PVP K15 and PVP K90. In addition, with increased PVP concentration, d100 and a0 continuously decreased. The mechanism of morphology evolution caused by the change in PVP concentration was investigated. The conversion rate of lauric acid with 1-butanol catalyzed by immobilized Porcine pancreatic lipase (PPL) was also evaluated. Results showed that PPL immobilized on amino-functionalized straight rod-shaped mesoporous silica maintained 50% of its esterification conversion rate even after five cycles of use with a maximum conversion rate was about 90.15%.

  14. Continuous lipase-catalyzed esterification of soybean fatty acids under ultrasound irradiation.

    PubMed

    Trentin, Claudia M; Scherer, Robison P; Dalla Rosa, C; Treichel, H; Oliveira, D; Oliveira, J Vladimir

    2014-05-01

    This work investigates the continuous production of alkyl esters from soybean fatty acid (FA) charges using immobilized Novozym 435 as catalyst. The experiments were performed in a packed-bed bioreactor evaluating the effects of FA charge to alcohol (methanol and ethanol) molar ratio, from 1:1 to 1:6, substrate flow rate in the range of 0.5-2.5 mL/min and output irradiation power up to 154 W, at fixed temperature of 65 °C, on the reaction conversion. Results showed that almost complete conversions to fatty acids ethyl esters were achieved at mild ultrasonic power (61.6 W), FA to ethanol molar ratio of 1:6, operating temperature (65 °C) and remained nearly constant for long-term reactions without negligible enzyme activity losses.

  15. Continuous lipase-catalyzed esterification of soybean fatty acids under ultrasound irradiation.

    PubMed

    Trentin, Claudia M; Scherer, Robison P; Dalla Rosa, C; Treichel, H; Oliveira, D; Oliveira, J Vladimir

    2014-05-01

    This work investigates the continuous production of alkyl esters from soybean fatty acid (FA) charges using immobilized Novozym 435 as catalyst. The experiments were performed in a packed-bed bioreactor evaluating the effects of FA charge to alcohol (methanol and ethanol) molar ratio, from 1:1 to 1:6, substrate flow rate in the range of 0.5-2.5 mL/min and output irradiation power up to 154 W, at fixed temperature of 65 °C, on the reaction conversion. Results showed that almost complete conversions to fatty acids ethyl esters were achieved at mild ultrasonic power (61.6 W), FA to ethanol molar ratio of 1:6, operating temperature (65 °C) and remained nearly constant for long-term reactions without negligible enzyme activity losses. PMID:24078183

  16. Stepwise esterification of phytosterols with conjugated linoleic acid catalyzed by Candida rugosa lipase in solvent-free medium.

    PubMed

    Torres, Carlos F; Torrelo, Guzman; Vazquez, Luis; Señorans, F Javier; Reglero, Guillermo

    2008-12-01

    We conducted a near quantitative esterification of phytosterols from soybean oil deodorizer distillate with conjugated linoleic acid. We used a 1:1 molar ratio of sterols to conjugated linoleic acid. For that matter, stepwise addition of sterols was investigated. Total sterols were divided into several portions and added sequentially to the reaction mixture. Using this methodology, purities of up to 80% steryl esters were obtained that consumed more than 90% of the total conjugated linoleic acid. In addition, the effects of temperature, amount, and stability of lipase were also evaluated. PMID:19134551

  17. One-step production of biodiesel from rice bran oil catalyzed by chlorosulfonic acid modified zirconia via simultaneous esterification and transesterification.

    PubMed

    Zhang, Yue; Wong, Wing-Tak; Yung, Ka-Fu

    2013-11-01

    Due to the high content (25-50%) of free fatty acid (FFA), crude rice bran oil usually requires a two steps conversion or one step conversion with very harsh condition for simultaneous esterification and transesterification. In this study, chlorosulfonic acid modified zirconia (HClSO3-ZrO2) with strong acidity and durability is prepared and it shows excellent catalytic activity toward simultaneous esterification and transesterification. Under a relative low reaction temperature of 120 °C, HClSO3-ZrO2 catalyzes a complete conversion of simulated crude rice bran oil (refined oil with 40 wt% FFA) into biodiesel and the conversion yield keep at above 92% for at least three cycles. Further investigation on the tolerance towards FFA and water reveals that it maintains high activity even with the presence of 40 wt% FFA and 3 wt% water. It shows that HClSO3-ZrO2 is a robust and durable catalyst which shows high potential to be commercial catalyst for biodiesel production from low grade feedstock.

  18. Kinetic modeling of lipase-catalyzed esterification reaction between oleic acid and trimethylolpropane: a simplified model for multi-substrate multi-product ping-pong mechanisms.

    PubMed

    Bornadel, Amin; Akerman, Cecilia Orellana; Adlercreutz, Patrick; Hatti-Kaul, Rajni; Borg, Niklas

    2013-01-01

    Kinetic models are among the tools that can be used for optimization of biocatalytic reactions as well as for facilitating process design and upscaling in order to improve productivity and economy of these processes. Mechanism pathways for multi-substrate multi-product enzyme-catalyzed reactions can become very complex and lead to kinetic models comprising several tens of terms. Hence the models comprise too many parameters, which are in general highly correlated and their estimations are often prone to huge errors. In this study, Novozym(®) 435 catalyzed esterification reaction between oleic acid (OA) and trimethylolpropane (TMP) with continuous removal of side-product (water) was carried out as an example for reactions that follow multi-substrate multi-product ping-pong mechanisms. A kinetic model was developed based on a simplified ping-pong mechanism proposed for the reaction. The model considered both enzymatic and spontaneous reactions involved and also the effect of product removal during the reaction. The kinetic model parameters were estimated using nonlinear curve fitting through unconstrained optimization methodology and the model was verified by using empirical data from different experiments and showed good predictability of the reaction under different conditions. This approach can be applied to similar biocatalytic processes to facilitate their optimization and design.

  19. Esterification of acrylic acid with methanol

    SciTech Connect

    Chubarov, G.A.; Danov, S.M.; Logutov, V.I.; Obmelyukhina, T.N.

    1984-01-01

    The esterification of acrylic acid with methanol in the absence of catalysis by strong mineral acids has been studied. The esterification rate was estimated from the amount of methyl acrylate formed at the end of a definite time, and the reaction rate was found to be first order with respect to methanol and second order with respect to acrylic acid. Mathematical relationships in good agreement with experimental data were derived from the results of the kinetic studies.

  20. Lipase catalyzed esterification of glycidol in organic solvents

    SciTech Connect

    Martins, J.F.; Nunes da Ponte, M.; Barreiros, S. . Centro de Tecnologia Quimica e Biologica)

    1993-08-05

    The authors studied the resolution of racemic glycidol through esterification with butyric acid catalyzed by porcine pancreatic lipase in organic media. A screening of seven solvents (log P values between 0.49 and 3.0, P being the n-octanol-water partition coefficient of the solvent) showed that neither log P nor the logarithm of the molar solubility of water in the solvent provides good correlations between enantioselectivity and the properties of the organic media. Chloroform was one of the best solvents as regards the enantiometic purity (e.p.) of the ester produced. In this solvent, the optimum temperature for the reaction was determined to be 35C. The enzyme exhibited maximum activity at a water content of 13 [plus minus] 2% (w/w). The enantiomeric purity obtained was 83 [plus minus] 2% of (S)-glycidol butyrate and did not depend on the alcohol concentration or the enzyme water content for values of these parameters up to 200 mM and 25% (w/w), respectively. The reaction was found to follow a BiBi mechanism.

  1. Lipase catalyzed esterification of glycidol in organic solvents.

    PubMed

    Martins, J F; Da Ponte, M N; Barreiros, S

    1993-08-01

    We studied the resolution of racemic glycidol through esterification with butyric acid catalyzed by porcine pancreatic lipase in organic media. A screening of seven solvents (log P values between 0.49 and 3.0, P being the n-octanol-water partition coefficient of the solvent) showed that neither log P nor the logarithm of the molar solubility of water in the solvent provides good correlations between enantioselectivity and the properties of the organic media. Chloroform was one of the best solvents as regards the enantiomeric purity (e. p.) of the ester produced. In this solvent, the optimum temperature for the reaction was determined to be 35 degrees C. The enzyme exhibited maximum activity at a water content of 13 +/- 2% (w/w). The enantiomeric purity obtained was 83 +/- 2% of (S)-glycidyl butyrate and did not depend on the alcohol concentration or the enzyme water content for values of these parameters up to 200 mM and 25% (w/w), respectively. The reaction was found to follow a BiBi mechanism.

  2. Esterification by the Plasma Acidic Water: Novel Application of Plasma Acid

    NASA Astrophysics Data System (ADS)

    Gu, Ling

    2014-03-01

    This work explores the possibility of plasma acid as acid catalyst in organic reactions. Plasma acidic water was prepared by dielectric barrier discharge and used to catalyze esterification of n-heptanioc acid with ethanol. It is found that the plasma acidic water has a stable and better performance than sulfuric acid, meaning that it is an excellent acid catalyst. The plasma acidic water would be a promising alternative for classic mineral acid as a more environment friendly acid.

  3. Vapor-phase esterification catalyzed by decationized Y zeolites

    SciTech Connect

    Santacesaria, E.; Gelosa, D.; Danise, P.; Carra, S.

    1983-04-01

    The kinetics of acetic acid esterification with ethyl alcohol, in vapor phase, have been studied in the presence of decationized Y zeolite catalysts. Two kinetic models have been considered: a Rideal model and a bimolecular surface reaction model. Both of these models satisfactorily fit the experimental data. The choice of the better model has been made on the basis of the physical significance of the parameters obtained by nonlinear regression analysis of the data. Suggestions are given on the mechanism of the reaction, which appears to be similar to that occurring under homogeneous liquid-phase conditions.

  4. Hydrosilane and bismuth-accelerated palladium catalyzed aerobic oxidative esterification of benzylic alcohols with air.

    PubMed

    Bai, Xing-Feng; Ye, Fei; Zheng, Long-Sheng; Lai, Guo-Qiao; Xia, Chun-Gu; Xu, Li-Wen

    2012-09-01

    In a palladium-catalyzed oxidative esterification, hydrosilane can serve as an activator of palladium catalyst with bismuth, thus leading to a novel ligand- and silver-free palladium catalyst system for facile oxidative esterification of a variety of benzylic alcohols in good yields.

  5. Hydrosilane and bismuth-accelerated palladium catalyzed aerobic oxidative esterification of benzylic alcohols with air.

    PubMed

    Bai, Xing-Feng; Ye, Fei; Zheng, Long-Sheng; Lai, Guo-Qiao; Xia, Chun-Gu; Xu, Li-Wen

    2012-09-01

    In a palladium-catalyzed oxidative esterification, hydrosilane can serve as an activator of palladium catalyst with bismuth, thus leading to a novel ligand- and silver-free palladium catalyst system for facile oxidative esterification of a variety of benzylic alcohols in good yields. PMID:22814568

  6. Heterogeneous catalytic esterification of omega-sulfhydryl fatty acids: Avoidance of thioethers, thioesters, and disulfides

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Two mesoporous silicas functionalized with propylsulfonic (SBA-15-PSA) and arenesulfonic (SBA-15-ASA) acid groups, and a highly acidic, functionalized styrene divinylbenzene copolymer ion exchange resin (Amberlyst-15) were examined for their ability to catalyze the ethanolic esterification of the N-...

  7. A solid acid esterification catalyst which reduces waste and increases yields

    SciTech Connect

    Lundquist, E.G.

    1993-12-31

    Recent research on polymeric catalysts has led to the development of a new solid acid esterification catalyst which is highly active for the esterification of fatty acids and maleic anhydride at elevated temperatures. The use of this catalyst eliminates the need for a final neutralization step which is required when using traditional homogenous acid (H{sub 2}SO{sub 4} and HCl) catalysts. This neutralization step generates large amounts of waste salts and hurts efficiency since unconsumed organic acid reactants are also neutralized. In the high temperature esterification reactions studied here, the production of dialkyl ether by-products from the acid catalyzed self-condensation of alcohol is also greatly reduced allowing for both high activity and selectivity.

  8. A Mini-Review on Solid Acid Catalysts for Esterification Reactions

    NASA Astrophysics Data System (ADS)

    Sirsam, Rajkumar; Hansora, Dharmesh; Usmani, Ghayas A.

    2016-04-01

    This paper presents an overview of research pertaining to solid acid catalysts for esterification reactions. Prominence has been given to the literatures that have been appeared during the last two decades. A variety of reactions catalyzed by solid acid catalysts have been tabulated according to their broad classification; industrially important reactions have been outlined. Examples, where the use of various solid acid catalysts have led to an improvement in the selectivity of the desired products, have also been discussed. Various catalyzed esterification reactions using different approaches and previous kinetic studies have been reviewed. Types, preparation and synthesis of various solid acid catalysts have been reviewed and discussed. Suggestions have been summarized for their implementation in future work.

  9. Enzymatic esterification of tapioca maltodextrin fatty acid ester.

    PubMed

    Udomrati, Sunsanee; Gohtani, Shoichi

    2014-01-01

    In this work new types of hydrophobically modified maltodextrin were prepared by enzyme-catalyzed reaction of maltodextrin and three fatty acids: decanoic acid (C-10), lauric acid (C-12) and palmitic acid (C-16). Lipase obtained from Thermomyces lanuginosus was found to be a useful biocatalyst in the maltodextrin esterification. Esterified maltodextrin with a degree of substitution (DS) 0.015-0.084 was prepared at the optimum conditions of 60 °C for 4 h. The DS was found to be at its highest when maltodextrin and fatty acids were taken in the ratio 1:0.5. The functional properties of these esterified maltodextrin were investigated. All esterified maltodextrin did not completely dissolve in water. Esterified maltodextrin at a concentration of 25% (w/w) exhibited Newtonian flow behavior similar to that of native maltodextrin. Esterified maltodextrin had a higher viscosity compare to native maltodextrin. X-ray diffraction pattern of esterified maltodextrin indicated crystallization of the fatty acid side chains. The thermal stability of esterified maltodextrin was checked by differential scanning calorimetry (DSC). Esterified maltodextrin was then used as an emulsifier to make n-hexadecane O/W emulsions. The emulsions were characterized according to their oil droplet characteristics and emulsification index.

  10. Chemoselective esterification of phenolic acids and alcohols.

    PubMed

    Appendino, Giovanni; Minassi, Alberto; Daddario, Nives; Bianchi, Federica; Tron, Gian Cesare

    2002-10-31

    [formula: see text] The Mitsunobu reaction can distinguish between alcohol and phenol hydroxyls in esterification reactions, providing an expeditious and broadly applicable entry into various phenolics and polyphenolics of biomedical and nutritional relevance.

  11. High-yield preparation of wax esters via lipase-catalyzed esterification using fatty acids and alcohols from crambe and camelina oils.

    PubMed

    Steinke, G; Weitkamp, P; Klein, E; Mukherjee, K D

    2001-02-01

    Fatty acids obtained from seed oils of crambe (Crambe abyssinica) and camelina (Camelina sativa) via alkaline saponification or steam splitting were esterified using lipases as biocatalysts with oleyl alcohol and the alcohols derived from crambe and camelina oils via hydrogenolysis of their methyl esters. Long-chain wax esters were thus obtained in high yields when Novozym 435 (immobilized lipase B from Candida antarctica) and papaya (Carica papaya) latex lipase were used as biocatalysts and vacuum was applied to remove the water formed. The highest conversions to wax esters were obtained with Novozym 435 (> or =95%) after 4-6 h of reaction, whereas with papaya latex lipase such a high degree of conversion was attained after 24 h. Products obtained from stoichiometric amounts of substrates were almost exclusively (>95%) composed of wax esters having compositions approaching that of jojoba (Simmondsia chinensis) oil, especially when crambe fatty acids in combination with camelina alcohols or camelina fatty acids in combination with crambe alcohols were used as substrates.

  12. Catalytic actions of alkaline salts in reactions between 1,2,3,4-butanetetracarboxylic acid and cellulose: II. Esterification.

    PubMed

    Ji, Bolin; Tang, Peixin; Yan, Kelu; Sun, Gang

    2015-11-01

    1,2,3,4-Butanetetracarboxylic acid (BTCA) reacts with cellulose in two steps with catalysis of alkaline salts such as sodium hypophosphite: anhydride formation and esterification of anhydride with cellulose. The alkali metal ions were found effective in catalyzing formation of BTCA anhydride in a previous report. In this work, catalytic functions of the alkaline salts in the esterification reaction between BTCA anhydride and cellulose were investigated. Results revealed that acid anions play an important role in the esterification reaction by assisting removal of protons on intermediates and completion of the esterification between cellulose and BTCA. Besides, alkaline salts with lower pKa1 values of the corresponding acids are more effective ones for the reaction since addition of these salts could lead to lower pH values and higher acid anion concentrations in finishing baths. The mechanism explains the results of FTIR and wrinkle recovery angles of the fabrics cured under different temperatures and times.

  13. Efficient water removal in lipase-catalyzed esterifications using a low-boiling-point azeotrope.

    PubMed

    Yan, Youchun; Bornscheuer, Uwe T; Schmid, Rolf D

    2002-04-01

    High conversions in lipase-catalyzed syntheses of esters from free acyl donors and an alcohol requires efficient removal of water preferentially at temperatures compatible to enzyme activity. Using a lipase B from Candida antarctica (CAL-B)-mediated synthesis of sugar fatty-acid esters, we show that a mixture of ethyl methylketone (EMK) and hexane (best ratio: 4:1, vo/vo) allows efficient removal of water generated during esterification. Azeotropic distillation of the solvent mixture (composition: 26% EMK, 55% hexane, 19% water) takes place at 59 degrees C, which closely matches the optimum temperature reported for CAL-B. Water is then removed from the azeotrope by membrane vapor permeation. In case of glucose stearate, 93% yield was achieved after 48 h using an equimolar ratio of glucose and stearic acid. CAL-B could be reused for seven reaction cycles, with 86% residual activity after 14 d total reaction time at 59 degrees C. A decrease in fatty-acid chain length as well as increasing temperatures (75 degrees C) resulted in lower conversions. In addition, immobilization of CAL-B on a magnetic polypropylene carrier (EP 100) facilitated separation of the biocatalyst.

  14. Cu(II)-catalyzed esterification reaction via aerobic oxidative cleavage of C(CO)-C(alkyl) bonds.

    PubMed

    Ma, Ran; He, Liang-Nian; Liu, An-Hua; Song, Qing-Wen

    2016-02-01

    A novel Cu(II)-catalyzed aerobic oxidative esterification of simple ketones for the synthesis of esters has been developed with wide functional group tolerance. This process is assumed to go through a tandem sequence consisting of α-oxygenation/esterification/nucleophilic addition/C-C bond cleavage and carbon dioxide is released as the only byproduct.

  15. Factors affecting the resolution of dl-menthol by immobilized lipase-catalyzed esterification in organic solvent.

    PubMed

    Wang, Dong-Lin; Nag, Ahindra; Lee, Guan-Chun; Shaw, Jei-Fu

    2002-01-16

    Among 10 lipases tested, Candida rugosa lipase exhibited the best ability to catalyze the resolution of dl-menthol in organic solvent. The lipase was immobilized on different carriers, and the experiment was carried out with different acyl donors. The high yield and optical purity of the product were achieved in cyclohexane with valeric acid as acyl donor using C. rugosa lipase immobilized on DEAE-Sephadex A-25. The conversion of dl-menthol depended on the water content of immobilized lipase and on the pH of the aqueous solution from which lipase was immobilized. The operational stability of the DEAE-Sephadex A-25 immobilized lipase in catalysis of the esterification reaction showed that >85% activity remained after 34 days of repeated use. The resolution of racemic menthol in organic medium catalyzed by immobilized C. rugosa lipase-catalyzed esterification is very convenient, and it represents a significant improvement in the use of enzyme for the preparative production of optically active menthol. This process is readily applicable to large-scale preparation. PMID:11782192

  16. Comparison of acid anhydrides with carboxylic acids in enantioselective enzymatic esterification of racemic menthol.

    PubMed

    Xu, J; Zhu, J; Kawamoto, T; Atsuo, T; Hu, Y

    1997-01-01

    Optical resolution of racemic menthol has been efficiently achieved by lipase-catalyzed enantioselective esterification in an organic solvent. The performance of the reaction using an acid anhydride as an acyl donor was compared with that using its corresponding free acid. The reactivities of acid anhydrides were found to be higher than their corresponding free acids, but acid anhydrides were also found to be easily hydrolyzed into free acids under the catalysis of the same enzyme. The existence of a too-high concentration of an acid anhydride in a micro-aqueous reaction system will cause dehydration and thus deactivation of the enzyme, and will enhance non-selective esterification of a chiral alcohol, which will reduce the optical purity of the product. All these drawbacks, however, could be effectively overcome in a semi-batch reaction system into which propionic anhydride was continuously fed. This system showed some advantages over a batch reaction system using free propionic acid: the reaction time of dl-menthol was shortened by half, the stability of the enzyme was much enhanced, and the optical purity of the product (l-menthyl ester) was kept at a similarly high level (> 98% ee). PMID:9631262

  17. Mechanistic investigation of the uncatalyzed esterification reaction of acetic acid and acid halides with methanol: a DFT study.

    PubMed

    Lawal, Monsurat M; Govender, Thavendran; Maguire, Glenn E M; Honarparvar, Bahareh; Kruger, Hendrik G

    2016-10-01

    Implementation of catalysts to drive reactions from reactants to products remains a burden to synthetic and organic chemists. In spite of investigations into the kinetics and mechanism of catalyzed esterification reactions, less effort has been made to explore the possibility of an uncatalyzed esterification process. Therefore, a comprehensive mechanistic perspective for the uncatalyzed mechanism at the molecular level is presented. Herein, we describe the non-catalyzed esterification reaction of acetic acid and its halide derivatives (XAc, where X= OH, F, Cl, Br, I) with methanol (MeOH) through a concerted process. The reaction in vacuum and methanol was performed using the density functional theory (DFT) method at M06-2X level with def2-TZVP basis set after a careful literature survey and computations. Esterification through cyclic 4- or 6-membered transition state structures in one- or two-step concerted mechanisms were investigated. The present study outlines the possible cyclic geometry conformations that may occur during experiments at simple ratio of reactants. The free energy of activation for acetic acid and acetyl chloride are 36 kcal mol(-1) and 21 kcal mol(-1), respectively. These are in good agreement with available experimental results from the literature. The selected quantum chemical descriptors proved to be useful tools in chemical reactivity prediction for the reaction mechanism. This quantum mechanics study can serve as a necessary step towards revisiting uncatalyzed reaction mechanisms in some classical organic reactions. PMID:27604278

  18. Controlled methyl-esterification of pectin catalyzed by cation exchange resin.

    PubMed

    Peng, Xiaoxia; Yang, Guang; Fan, Xingchen; Bai, Yeming; Ren, Xiaomeng; Zhou, Yifa

    2016-02-10

    This study developed a new method to methyl-esterify pectin using a cation exchange resin. Homogalacturonan (HG)-type pectin (WGPA-3-HG) and rhamnogalacturonan (RG)-I-type pectin (AHP-RG) obtained from the roots of Panax ginseng and sunflower heads, respectively, were used as models. Compared to commonly used methyl-esterification methods that use either methyl iodide or acidified methanol, the developed method can methyl-esterify both HG- and RG-I-type pectins without degrading their structures via β-elimination or acid hydrolysis. In addition, by modifying reaction conditions, including the mass ratio of resin to pectin, reaction time, and temperature, the degree of esterification can be controlled. Moreover, the resin and methanol can be recycled to conserve resources, lower costs, and reduce environmental pollution. This new methodology will be highly useful for industrial esterification of pectin. PMID:26686175

  19. Direct dehydrative esterification of alcohols and carboxylic acids with a macroporous polymeric acid catalyst.

    PubMed

    Minakawa, Maki; Baek, Heeyoel; Yamada, Yoichi M A; Han, Jin Wook; Uozumi, Yasuhiro

    2013-11-15

    A macroporous polymeric acid catalyst was prepared for the direct esterification of carboxylic acids and alcohols that proceeded at 50-80 °C without removal of water to give the corresponding esters with high yield. Flow esterification for the synthesis of biodiesel fuel was also achieved by using a column-packed macroporous acid catalyst under mild conditions without removal of water.

  20. Study of reaction parameters and kinetics of esterification of lauric acid with butanol by immobilized Candida antarctica lipase.

    PubMed

    Shankar, Sini; Agarwal, Madhu; Chaurasia, S P

    2013-12-01

    Esterification of lauric acid with n-butanol, catalyzed by immobilized Candida antarctica lipase (CAL) in aqueous-organic biphasic solvent system was studied. Effects of various reaction parameters on esterification were investigated, such as type and amount of solvent, amount of buffer, pH, temperature, speed of agitation, amount of enzyme, butanol and lauric acid. The most suitable reaction conditions for esterification were observed at 50 degrees C and pH 7.0 using 5000 micromoles of lauric acid, 7000 pmoles of butanol, 0.25 ml phosphate buffer, 1 ml of isooctane as the solvent and 50 mg of immobilized enzyme in the reaction medium at agitation speed of 150 rpm. Maximum esterification of 96.36% was acheived in 600 min of reaction time at n-butanol to lauric acid molar ratio of 1: 0.7. Kinetic study for the esterification of lauric acid with n-butanol using immobilized CAL was carried out and the kinetic constants were estimated by using non-linear regression method. The estimated value of Michaelis kinetic constants for butanol (KmBt) and acid (KmAc) were 451.56 (M) and 4.7 x 10(-7)(M), respectively and the value of dissociation constant (KBt) of the butanol-lipase complex was 9.41 x 10(7)(M). The estimated constants agreed fairly well with literature data.

  1. Biodiesel from Citrullus colocynthis Oil: Sulfonic-Ionic Liquid-Catalyzed Esterification of a Two-Step Process

    PubMed Central

    Ali Elsheikh, Yasir; Hassan Akhtar, Faheem

    2014-01-01

    Biodiesel was prepared from Citrullus colocynthis oil (CCO) via a two-step process. The first esterification step was explored in two ionic liquids (ILs) with 1,3-disulfonic acid imidazolium hydrogen sulfate (DSIMHSO4) and 3-methyl-1-sulfonic acid imidazolium hydrogen sulfate (MSIMHSO4). Both ILs appeared to be good candidates to replace hazardous acidic catalyst due to their exceptional properties. However, the two sulfonic chains existing in DSIMHSO4 were found to increase the acidity to the IL than the single sulfonic chain in MSIMHSO4. Based on the results, 3.6 wt% of DSIMHSO4, methanol/CCO molar ratio of 12 : 1, and 150°C offered a final FFA conversion of 95.4% within 105 min. A 98.2% was produced via second KOH-catalyzed step in 1.0%, 6 : 1 molar ratio, 600 rpm, and 60°C for 50 min. This new two-step catalyzed process could solve the corrosion and environmental problems associated with the current acidic catalysts. PMID:24987736

  2. Biodiesel from Citrullus colocynthis oil: sulfonic-ionic liquid-catalyzed esterification of a two-step process.

    PubMed

    Ali Elsheikh, Yasir; Hassan Akhtar, Faheem

    2014-01-01

    Biodiesel was prepared from Citrullus colocynthis oil (CCO) via a two-step process. The first esterification step was explored in two ionic liquids (ILs) with 1,3-disulfonic acid imidazolium hydrogen sulfate (DSIMHSO4) and 3-methyl-1-sulfonic acid imidazolium hydrogen sulfate (MSIMHSO4). Both ILs appeared to be good candidates to replace hazardous acidic catalyst due to their exceptional properties. However, the two sulfonic chains existing in DSIMHSO4 were found to increase the acidity to the IL than the single sulfonic chain in MSIMHSO4. Based on the results, 3.6 wt% of DSIMHSO4, methanol/CCO molar ratio of 12 : 1, and 150 °C offered a final FFA conversion of 95.4% within 105 min. A 98.2% was produced via second KOH-catalyzed step in 1.0%, 6 : 1 molar ratio, 600 rpm, and 60 °C for 50 min. This new two-step catalyzed process could solve the corrosion and environmental problems associated with the current acidic catalysts.

  3. Synthesis of rosin acid starch catalyzed by lipase.

    PubMed

    Lin, Rihui; Li, He; Long, Han; Su, Jiating; Huang, Wenqin

    2014-01-01

    Rosin, an abundant raw material from pine trees, was used as a starting material directly for the synthesis of rosin acid starch. The esterification reaction was catalyzed by lipase (Novozym 435) under mild conditions. Based on single factor experimentation, the optimal esterification conditions were obtained as follows: rosin acid/anhydrous glucose unit in the molar ratio 2:1, reaction time 4 h at 45°C, and 15% of lipase dosage. The degree of substitution (DS) reaches 0.098. Product from esterification of cassava starch with rosin acid was confirmed by FTIR spectroscopy and iodine coloration analysis. Scanning electron microscopy and X-ray diffraction analysis showed that the morphology and crystallinity of the cassava starch were largely destroyed. Thermogravimetric analysis indicated that thermal stability of rosin acid starch decreased compared with native starch.

  4. Reactive Distillation for Esterification of Bio-based Organic Acids

    SciTech Connect

    Fields, Nathan; Miller, Dennis J.; Asthana, Navinchandra S.; Kolah, Aspi K.; Vu, Dung; Lira, Carl T.

    2008-09-23

    The following is the final report of the three year research program to convert organic acids to their ethyl esters using reactive distillation. This report details the complete technical activities of research completed at Michigan State University for the period of October 1, 2003 to September 30, 2006, covering both reactive distillation research and development and the underlying thermodynamic and kinetic data required for successful and rigorous design of reactive distillation esterification processes. Specifically, this project has led to the development of economical, technically viable processes for ethyl lactate, triethyl citrate and diethyl succinate production, and on a larger scale has added to the overall body of knowledge on applying fermentation based organic acids as platform chemicals in the emerging biorefinery. Organic acid esters constitute an attractive class of biorenewable chemicals that are made from corn or other renewable biomass carbohydrate feedstocks and replace analogous petroleum-based compounds, thus lessening U.S. dependence on foreign petroleum and enhancing overall biorefinery viability through production of value-added chemicals in parallel with biofuels production. Further, many of these ester products are candidates for fuel (particularly biodiesel) components, and thus will serve dual roles as both industrial chemicals and fuel enhancers in the emerging bioeconomy. The technical report from MSU is organized around the ethyl esters of four important biorenewables-based acids: lactic acid, citric acid, succinic acid, and propionic acid. Literature background on esterification and reactive distillation has been provided in Section One. Work on lactic acid is covered in Sections Two through Five, citric acid esterification in Sections Six and Seven, succinic acid in Section Eight, and propionic acid in Section Nine. Section Ten covers modeling of ester and organic acid vapor pressure properties using the SPEAD (Step Potential

  5. Lipase in biphasic alginate beads as a biocatalyst for esterification of butyric acid and butanol in aqueous media.

    PubMed

    Ng, Choong Hey; Yang, Kun-Lin

    2016-01-01

    Esterification of organic acids and alcohols in aqueous media is very inefficient due to thermodynamic constraints. However, fermentation processes used to produce organic acids and alcohols are often conducted in aqueous media. To produce esters in aqueous media, biphasic alginate beads with immobilized lipase are developed for in situ esterification of butanol and butyric acid. The biphasic beads contain a solid matrix of calcium alginate and hexadecane together with 5 mg/mL of lipase as the biocatalyst. Hexadecane in the biphasic beads serves as an organic phase to facilitate the esterification reaction. Under optimized conditions, the beads are able to catalyze the production of 0.16 mmol of butyl butyrate from 0.5 mmol of butyric acid and 1.5 mmol of butanol. In contrast, when monophasic beads (without hexadecane) are used, only trace amount of butyl butyrate is produced. One main application of biphasic beads is in simultaneous fermentation and esterification (SFE) because the organic phase inside the beads is very stable and does not leach out into the culture medium. SFE is successfully conducted with an esterification yield of 6.32% using biphasic beads containing iso-octane even though the solvent is proven toxic to the butanol-producing Clostridium spp. PMID:26672465

  6. Kinetics of the catalytic esterification of diglycerin with capric acid

    SciTech Connect

    Trufanova, T.N.; Nechesnyuk, G.P.; Bumina, N.A.; Kruchinin, V.A.; Slapygina, O.L.

    1988-06-10

    The object of this investigation was a further study of the rate of esterification of polyglycerins with fatty acids in the presence of acids, organometallic compounds, and metal salts. The catalytic effects of the following substances were studied (in wt. % of the reaction mixture): potassium, magnesium, copper, and zinc sulfates (analytical grade) first dried by calcination, 1%; pure grade tetrabutoxytitanate, 0.5-1%; and pure grade p-toluenesulfonic acid, recrystallized from concentrated hydrochloric acid, 1.0-3%. Samples taken after measured time intervals were analyzed by titration with an alcoholic solution of potassium hydroxide. The investigation was carried out in the kinetic regime.

  7. Catalytic esterification of methacrylic acid with methyl alcohol

    SciTech Connect

    Lunin, A.F.; Zheleznaya, L.L.; Karakhanov, R.A.; Meshcheryakov, S.V.; Magadov, R.S.; Mkrtychan, V.R.; Fomin, V.A.

    1987-08-10

    The authors contend that virtually all methods for the production of methacrylic acid esters suffer from the drawbacks of low conversion, dependence on costly catalysts, low feed rates, and the need to use inhibitors in the process. To eliminate these drawbacks, they propose and test a new catalyst, sulfopolyphenyl ketone, which contains an extensive conjugated bond system together with ionic hydroxide groups. The catalytic esterification rate and yield is given for this catalyst and chromatography is performed for the resulting esters.

  8. Accelerated esterification of free fatty acid using pulsed microwaves.

    PubMed

    Kim, Daeho; Choi, Jinju; Kim, Geun-Ju; Seol, Seung Kwon; Jung, Sunshin

    2011-07-01

    It was demonstrated that pulsed microwave irradiation is a more effective method to accelerate the esterification of free fatty acid with a heterogeneous catalyst than continuous microwave irradiation. A square-pulsed microwave with a 400 Hz repetition rate and a 10-20% duty cycle with the same energy as the continuous microwave were used in this study. The pulsed microwaves improved the esterification conversion from 39.9% to 66.1% after 15 min in comparison with the continuous microwave under the same reaction conditions. These results indicated that pulsed microwaves with repetitive strong power could enhance the efficiency of biodiesel production relative to the use of continuous microwave with mild power.

  9. Determination of Free Fatty Acids and Triglycerides by Gas Chromatography Using Selective Esterification Reactions

    SciTech Connect

    Kail, Brian W; Link, Dirk D; Morreale, Bryan D

    2012-11-01

    A method for selectively determining both free fatty acids (FFA) and triacylglycerides (TAGs) in biological oils was investigated and optimized using gas chromatography after esterification of the target species to their corresponding fatty acid methyl esters (FAMEs). The method used acid catalyzed esterification in methanolic solutions under conditions of varying severity to achieve complete conversion of more reactive FFAs while preserving the concentration of TAGs. Complete conversion of both free acids and glycerides to corresponding FAMEs was found to require more rigorous reaction conditions involving heating to 120°C for up to 2 h. Method validation was provided using gas chromatography–flame ionization detection, gas chromatography–mass spectrometry, and liquid chromatography–mass spectrometry. The method improves on existing methods because it allows the total esterified lipid to be broken down by FAMEs contributed by FFA compared to FAMEs from both FFA and TAGs. Single and mixed-component solutions of pure fatty acids and triglycerides, as well as a sesame oil sample to simulate a complex biological oil, were used to optimize the methodologies. Key parameters that were investigated included: HCl-to-oil ratio, temperature and reaction time. Pure free fatty acids were found to esterify under reasonably mild conditions (10 min at 50°C with a 2.1:1 HCl to fatty acid ratio) with 97.6 ± 2.3% recovery as FAMEs, while triglycerides were largely unaffected under these reaction conditions. The optimized protocol demonstrated that it is possible to use esterification reactions to selectively determine the free acid content, total lipid content, and hence, glyceride content in biological oils. This protocol also allows gas chromatography analysis of FAMEs as a more ideal analyte than glyceride species in their native state.

  10. High-yield synthesis of bioactive ethyl cinnamate by enzymatic esterification of cinnamic acid.

    PubMed

    Wang, Yun; Zhang, Dong-Hao; Zhang, Jiang-Yan; Chen, Na; Zhi, Gao-Ying

    2016-01-01

    In this paper, Lipozyme TLIM-catalyzed synthesis of ethyl cinnamate through esterification of cinnamic acid with ethanol was studied. In order to increase the yield of ethyl cinnamate, several media, including acetone, isooctane, DMSO and solvent-free medium, were investigated in this reaction. The reaction showed a high yield by using isooctane as reaction medium, which was found to be much higher than the yields reported previously. Furthermore, several parameters such as shaking rate, water activity, reaction temperature, substrate molar ratio and enzyme loading had important influences on this reaction. For instance, when temperature increased from 10 to 50 °C, the initial reaction rate increased by 18 times and the yield of ethyl cinnamate increased by 6.2 times. Under the optimum conditions, lipase-catalyzed synthesis of ethyl cinnamate gave a maximum yield of 99%, which was of general interest for developing industrial processes for the preparation of ethyl cinnamate.

  11. Recovery of acetic acid from dilute aqueous solutions using catalytic dehydrative esterification with ethanol.

    PubMed

    Yagyu, Daisuke; Ohishi, Tetsuo; Igarashi, Takeshi; Okumura, Yoshikuni; Nakajo, Tetsuo; Mori, Yuichiro; Kobayashi, Shū

    2013-03-01

    We have developed a direct esterification of aqueous acetic acid with ethanol (molar ratio=1:1) catalyzed by polystyrene-supported or homogeneous sulfonic acids toward the recovery of acetic acid from wastewater in chemical plants. The equilibrium yield was significantly increased by the addition of toluene, which had a high ability to extract ethyl acetate from the aqueous phase. It was shown that low-loading and alkylated polystyrene-supported sulfonic acid efficiently accelerated the reaction. These results suggest that the construction of hydrophobic reaction environments in water was critical in improving the chemical yield. Addition of inorganic salts was also effective for the reaction under not only biphasic conditions (toluene-water) but also toluene-free conditions, because the mutual solubility of ethyl acetate and water was suppressed by the salting-out effect. Among the tested salts, CaCl(2) was found to be the most suitable for this reaction system. PMID:23290939

  12. Enhanced antiamyloidal activity of hydroxy cinnamic acids by enzymatic esterification with alkyl alcohols.

    PubMed

    Kondo, Hazuki; Sugiyama, Haruka; Katayama, Shigeru; Nakamura, Soichiro

    2014-01-01

    Lipophilic derivatives of hydroxyl cinnamic acids (HCAs) including caffeic acid (CA), ferulic acid, sinapic acid (SA), and chlorogenic acid were synthesized by esterification with butanol, octanol, or hexadecanol catalyzed by the lipase from Candida antarctica to investigate the effect of lipophilicity on their antiamyloidal activity assessed by the inhibitory activities toward fibrillization of amyloid β (Aβ) peptide. Among them, CA showed the highest activity at 50 μM, reducing the amyloid fibril formation of Aβ to 34.4 ± 6.8%. The antiamyloidal effects of HCAs were enhanced by esterification with alkyl alcohols, and the longer alkyl chain tended to be more effective except for SA. Aβ fibril formation was suppressed by the hexadecyl ester of CA, which was reduced to 8.8 ± 2.3%. In contrast, those of octyl and butyl esters were 19.3 ± 2.3% and 41.6 ± 6.1%, respectively. These results show that lipophilicity plays an important role in the antiamyloidal activities of esterified phenolic compounds.

  13. Kinetic Modeling of Esterification of Ethylene Glycol with Acetic Acid

    NASA Astrophysics Data System (ADS)

    Yadav, Vishnu P.; Mukherjee, Rudra Palash; Bantraj, Kandi; Maity, Sunil K.

    2010-10-01

    The reaction kinetics of the esterification of ethylene glycol with acetic acid in the presence of cation exchange resin has been studied and kinetic models based on empirical and Langmuir approach has been developed. The Langmuir based model involving eight kinetic parameters fits experimental data much better compared to empirical model involving four kinetic parameters. The effect of temperature and catalyst loading on the reaction system has been analyzed. Further, the activation energy and frequency factor of the rate constants for Langmuir based model has been estimated.

  14. Kinetic Modeling of Esterification of Ethylene Glycol with Acetic Acid

    SciTech Connect

    Yadav, Vishnu P.; Maity, Sunil K.; Mukherjee, Rudra Palash; Bantraj, Kandi

    2010-10-26

    The reaction kinetics of the esterification of ethylene glycol with acetic acid in the presence of cation exchange resin has been studied and kinetic models based on empirical and Langmuir approach has been developed. The Langmuir based model involving eight kinetic parameters fits experimental data much better compared to empirical model involving four kinetic parameters. The effect of temperature and catalyst loading on the reaction system has been analyzed. Further, the activation energy and frequency factor of the rate constants for Langmuir based model has been estimated.

  15. Optimization of conjugated linoleic acid triglycerides via enzymatic esterification in no-solvent system

    NASA Astrophysics Data System (ADS)

    Yi, Dan; Sun, Xiuqin; Li, Guangyou; Liu, Fayi; Lin, Xuezheng; Shen, Jihong

    2009-09-01

    We compared four esterifiable enzymes. The lipase Novozym 435 possessed the highest activity for the conjugated linoleic acid esterification during the synthesis of triglycerides. The triglycerides were synthesized by esterification of glycerol and conjugated linoleic acid (CLA) in a no-solvent system using lipase catalysis. We investigated the effects of temperature, enzyme concentration, water content, and time on esterification. Enzyme and water concentrations of up to 1% of the total reaction volume and a system temperature of 60°C proved optimal for esterification. Similarly, when the esterification was carried out for 24 h, the reaction ratio improved to 94.11%. The esterification rate of the rotating screen basket remained high (87.28%) when the enzyme was re-used for the 5th time. We evaluated the substrate selectivity of lipase (NOVO 435) and determined that this lipase prefers the 10,12-octadacadienoic acid to the 9,11-octadecadienoic acid.

  16. Dialkyl 3,3'-thiodipropionate and dialkyl 2,2'-thiodiacetate antioxidants by lipase-catalyzed esterification and transesterification.

    PubMed

    Weber, Nikolaus; Klein, Erika; Vosmann, Klaus

    2006-04-19

    Medium- and long-chain dialkyl 3,3'-thiodipropionate antioxidants such as dioctyl 3,3'-thiodipropionate, didodecyl 3,3'-thiodipropionate, dihexadecyl 3,3'-thiodipropionate, and di-(cis-9-octadecenyl) 3,3'-thiodipropionate were prepared in high yield by lipase-catalyzed esterification and transesterification of 3,3'-thiodipropionic acid and its dimethyl ester, respectively, with the corresponding medium- or long-chain 1-alkanols, i.e., 1-octanol, 1-dodecanol, 1-hexadecanol, and cis-9-octadecen-1-ol, in vacuo (80 kPa) at moderate temperatures (60-80 degrees C) without solvents. Immobilized lipase B from Candida antarctica (Novozym 435) was the most active biocatalyst for the preparation of medium- and long-chain dialkyl 3,3'-thiodipropionates showing enzyme activities up to 1489 units/g, whereas the immobilized lipases from Rhizomucor miehei (Lipozyme RM IM) and Thermomyces lanuginosus (Lipozyme TL IM) were by far less active ( approximately 10 enzyme units/g). Maximum conversions to dialkyl 3,3'-thiodipropionates were as high as 92-98% after 4 h of reaction time. Similarly, dihexadecyl 2,2'-thiodiacetate was prepared in high yield using 2,2'-thiodiacetic acid or diethyl 2,2'-thiodiacetate and 1-hexadecanol as the starting materials and Novozym 435 as the biocatalyst. PMID:16608215

  17. Esterification of pseudoephedrine hydrochloride by citric acid in a solid dose pharmaceutical preparation.

    PubMed

    Goel, Alok; Zhao, Zhicheng; Sørensen, Dan; Zhou, Jay; Zhang, Fa

    2016-09-10

    Esterification of pseudoephedrine hydrochloride (PSE) by citric acid was observed in a solid dose pharmaceutical preparation at room temperature and accelerated stability condition (40°C/75% relative humidity). The esterification of PSE with citric acid was confirmed by a solid-state binary reaction in the presence of minor level of water at elevated temperature to generate three isomeric esters. The structures of the pseudoephedrine citric acid esters were elucidated using high-resolution mass spectrometry and nuclear magnetic resonance spectroscopy (NMR). Occurrence of esterification in solid state, instead of amidation which is generally more favorable than esterification, is likely due to remaining HCl salt form of solid pseudoephedrine hydrochloride to protect its amino group from amidation with citric acid. In contrast, the esterification was not observed from solution reaction between PSE and citric acid.

  18. Esterification of pseudoephedrine hydrochloride by citric acid in a solid dose pharmaceutical preparation.

    PubMed

    Goel, Alok; Zhao, Zhicheng; Sørensen, Dan; Zhou, Jay; Zhang, Fa

    2016-09-10

    Esterification of pseudoephedrine hydrochloride (PSE) by citric acid was observed in a solid dose pharmaceutical preparation at room temperature and accelerated stability condition (40°C/75% relative humidity). The esterification of PSE with citric acid was confirmed by a solid-state binary reaction in the presence of minor level of water at elevated temperature to generate three isomeric esters. The structures of the pseudoephedrine citric acid esters were elucidated using high-resolution mass spectrometry and nuclear magnetic resonance spectroscopy (NMR). Occurrence of esterification in solid state, instead of amidation which is generally more favorable than esterification, is likely due to remaining HCl salt form of solid pseudoephedrine hydrochloride to protect its amino group from amidation with citric acid. In contrast, the esterification was not observed from solution reaction between PSE and citric acid. PMID:27474946

  19. Catalysis of the hydrolysis of ethyl mandelate and esterification of alpha-bromopropionic acid by lipase in microemulsions.

    PubMed

    Xiao, H; Liu, J; Li, Z

    1993-01-01

    Candida cyclindracea lipase (CCL) was added to "sodium dodecyl sulfonate (AS)/n-butanol/n-octane/n-octane" water-in-oil microemulsion to catalyze the hydrolysis of ethyl mandelate and the esterification of alpha-bromopropionic acid with n-butanol, respectively. The catalytic activity of CCL in the above microemulsions was higher than that in the traditional oil/water biphasic systems. After hydrolysis for 48 h, the conversion rate of the reaction reached 90% and S-mandelic acid, [alpha]D20-149.8 (C10; H2O), optical purity ca. 97%, was isolated. While after esterification for 6 h, the conversion rate of the reaction reached 45%, and butyl-(R)-alpha-bromopropionate, [alpha]D20 18.2 (Cl; CHCl3), optical purity ca. 99%, was obtained.

  20. Preparation of a novel carbon-based solid acid from cassava stillage residue and its use for the esterification of free fatty acids in waste cooking oil.

    PubMed

    Wang, Lingtao; Dong, Xiuqin; Jiang, Haoxi; Li, Guiming; Zhang, Minhua

    2014-04-01

    A novel carbon-based solid acid catalyst was prepared by the sulfonation of incompletely carbonized cassava stillage residue (CSR) with concentrated sulfuric acid, and employed to catalyze the esterification of methanol and free fatty acids (FFAs) in waste cooking oil (WCO). The effects of the carbonization and the sulfonation temperatures on the pore structure, acid density and catalytic activity of the CSR-derived catalysts were systematically investigated. Low temperature carbonization and high temperature sulfonation can cause the collapse of the carbon framework, while high temperature carbonization is not conducive to the attachment of SO3H groups on the surface. The catalyst showed high catalytic activity for esterification, and the acid value for WCO is reduced to below 2mg KOH/g after reaction. The activity of catalyst can be well maintained after five cycles. CSR can be considered a promising raw material for the production of a new eco-friendly solid acid catalyst.

  1. Butyric acid esterification kinetics over Amberlyst solid acid catalysts: the effect of alcohol carbon chain length.

    PubMed

    Pappu, Venkata K S; Kanyi, Victor; Santhanakrishnan, Arati; Lira, Carl T; Miller, Dennis J

    2013-02-01

    The liquid phase esterification of butyric acid with a series of linear and branched alcohols is examined. Four strong cation exchange resins, Amberlyst™ 15, Amberlyst™ 36, Amberlyst™ BD 20, and Amberlyst™ 70, were used along with para-toluenesulfonic acid as a homogeneous catalyst. The effect of increasing alcohol carbon chain length and branching on esterification rate at 60°C is presented. For all catalysts, the decrease in turnover frequency (TOF) with increasing carbon chain length of the alcohol is described in terms of steric hindrance, alcohol polarity, and hydroxyl group concentration. The kinetics of butyric acid esterification with 2-ethylhexanol using Amberlyst™ 70 catalyst is described with an activity-based, pseudo-homogeneous kinetic model that includes autocatalysis by butyric acid.

  2. Preparation and characterization Al3+-bentonite Turen Malang for esterification fatty acid (palmitic acid, oleic acid and linoleic acid)

    NASA Astrophysics Data System (ADS)

    Abdulloh, Abdulloh; Aminah, Nanik Siti; Triyono, Mudasir, Trisunaryanti, Wega

    2016-03-01

    Catalyst preparation and characterization of Al3+-bentonite for esterification of palmitic acid, oleic acid and linoleic acid has been done. Al3+-bentonite catalyst was prepared from natural bentonite of Turen Malang through cation exchange reaction using AlCl3 solution. The catalysts obtained were characterized by XRD, XRF, pyridine-FTIR and surface area analyser using the BET method. Catalyst activity test of Al3+-bentonite for esterification reaction was done at 65°C using molar ratio of metanol-fatty acid of 30:1 and 0.25 g of Al3+-bentonite catalyst for the period of ½, 1, 2, 3, 4 and 5 hours. Based on the characterization results, the Al3+-bentonite Turen Malang catalyst has a d-spacing of 15.63 Ǻ, acid sites of Brönsted and Lewis respectively of 230.79 µmol/g and 99.39 µmol/g, surface area of 507.3 m2/g and the average of radius pore of 20.09 Å. GC-MS analysis results of the oil phase after esterification reaction showed the formation of biodiesel (FAME: Fatty acid methyl ester), namely methyl palmitate, methyl oleate and methyl linoleate. The number of conversions resulted in esterification reaction using Al3+-bentonite Turen Malang catalyst was 74.61%, 37.75%, and 20, 93% for the esterification of palmitic acid, oleic acid and linoleic acid respectively.

  3. Immobilized MAS1 lipase showed high esterification activity in the production of triacylglycerols with n-3 polyunsaturated fatty acids.

    PubMed

    Wang, Xiumei; Li, Daoming; Qu, Man; Durrani, Rabia; Yang, Bo; Wang, Yonghua

    2017-02-01

    Immobilization of lipase MAS1 from marine Streptomyces sp. strain W007 and its application in catalyzing esterification of n-3 polyunsaturated fatty acids (PUFA) with glycerol were investigated. The resin XAD1180 was selected as a suitable support for the immobilization of lipase MAS1, and its absorption ability was 75mg/g (lipase/resin ratio) with initial buffer pH value of 8.0. The thermal stability of immobilized MAS1 was improved significantly compared with that of the free lipase. Immobilized MAS1 had no regiospecificity in the hydrolysis of triolein. The highest esterification degree (99.31%) and TAG content (92.26%) by immobilized MAS1-catalyzed esterification were achieved under the optimized conditions, which were significantly better than those (82.16% and 47.26%, respectively) by Novozym 435. More than 92% n-3 PUFA was incorporated into TAG that had similar fatty acids composition to the substrate (n-3 PUFA). The immobilized MAS1 exhibited 50% of its initial activity after being used for five cycles. PMID:27596418

  4. Ultrasonic free fatty acids esterification in tobacco and canola oil.

    PubMed

    Boffito, D C; Galli, F; Pirola, C; Bianchi, C L; Patience, G S

    2014-11-01

    Ultrasound accelerates the free fatty acids esterification rate by reducing the mass transfer resistance between methanol in the liquid phase and absorbed organic species on Amberlyst®46 catalyst. The reaction rates of canola oil is three times greater than for tobacco seed oil but half the reaction rate of pure oleic acid as measured in a batch reactor. The beneficial effects of ultrasound vs. the conventional approach are more pronounced at lower temperatures (20°C and 40°C vs. 63°C): at 20°C, the free fatty acids conversion reaches 68% vs. 23% with conventional mechanical stirring. The increased conversion is attributed to acoustic cavitation that increases mass transfer in the vicinity of the active sites. The Eley-Rideal kinetic model in which the concentration of the reacting species is expressed taking into account the mass transfer between the phases is in excellent agreement with the experimental data. Ultrasound increases the mass transfer coefficient in the tobacco oil 6 and 4.1 fold at 20°C and 40°C, respectively.

  5. Enantioselective esterification of (R,S)-2-methylalkanoic acid with Carica papaya lipase in organic solvents.

    PubMed

    Chang, Chun-Sheng; Ho, Ssu-Ching

    2011-11-01

    Isooctane was the best reaction medium for the enantioselective esterification of (R,S)-2-methylalkanoic acid with n-butanol using Carica papaya lipase as catalyst. Increasing linear alkyl-chain length of racemic 2-methylalkanoic acids from ethyl to hexyl increased the enantioselectivity (E) from 2.1 to 98.2 for the esterification of racemic 2-methylalkanoic acids with n-butanol at 35°C. Decreasing reaction temperature from 40 to 20°C increased the enantioselectivity (E) from 14 to 33 for the esterification of racemic 2-methylhexanoic acids with n-butanol. We obtained a maximum enantioselectivity, of E = 24.3, for the enantioselective esterification of racemic 2-methylhexanoic acids with n-butanol in isooctane at water activity 0.33, and at 35°C.

  6. Chemoselective esterification and amidation of carboxylic acids with imidazole carbamates and ureas.

    PubMed

    Heller, Stephen T; Sarpong, Richmond

    2010-10-15

    Imidazole carbamates and ureas were found to be chemoselective esterification and amidation reagents. A wide variety of carboxylic acids were converted to their ester or amide analogues by a simple synthetic procedure in high yields.

  7. Cu-catalyzed esterification reaction via aerobic oxygenation and C-C bond cleavage: an approach to α-ketoesters.

    PubMed

    Zhang, Chun; Feng, Peng; Jiao, Ning

    2013-10-01

    The Cu-catalyzed novel aerobic oxidative esterification reaction of 1,3-diones for the synthesis of α-ketoesters has been developed. This method combines C-C σ-bond cleavage, dioxygen activation and oxidative C-H bond functionalization, as well as provides a practical, neutral, and mild synthetic approach to α-ketoesters which are important units in many biologically active compounds and useful precursors in a variety of functional group transformations. A plausible radical process is proposed on the basis of mechanistic studies.

  8. Preparation of mono- and diacylglycerols by enzymatic esterification of glycerol with conjugated linoleic acid in hexane.

    PubMed

    Martinez, C E; Vinay, J C; Brieva, R; Hill, C G; Garcia, H S

    2005-04-01

    Esterification of glycerol with conjugated linoleic acid (CLA) was carried out in hexane. Lipase from Rhizomucor miehei provided a high degree of esterification (80%) in 8 h at 50 degrees C when used at 15% (w/w) in a system containing a 1:2 molar ratio of glycerol to free fatty acids. Esterification levels >80% were obtained in 8 h at 40 degrees C with 15% (w/w) lipase from Candida antarctica at the same molar ratio of reactants. The extent of esterification of CLA was >90% after 4 h of reaction at 50 degrees C with a 5% (w/w) loading of either R. miehei or C. antarctica lipase, together with a 1:1 molar ratio of substrates. Both enzymes incorporated the original CLA as acylglycerol residues in primarily 1,3-diacylglycerol and 1-monoacylglycerol. The CLA-rich acylglycerols can be employed as emulsifiers or as substitutes for natural fats and oils.

  9. Lipase catalyzed esterification of glycidol in nonaqueous solvents: solvent effects on enzymatic activity.

    PubMed

    Martins, J F; de Sampaio, T C; de Carvalho, I B; Barreiros, S

    1994-06-01

    We studied the effect of organic solvents on the kinetics of porcine pancreatic lipase (pp) for the resolution of racemic glycidol through esterification with butyric acid. We quantified ppl hydration by measuring water sorption isotherms for the enzyme in the solvents/mixtures tested. The determination of initial rates as a function of enzyme hydration revealed that the enzyme exhibits maximum apparent activity in the solvents/mixtures at the same water content (9% to 11% w/w) within the associated experimental error. The maximum initial rates are different in all the media and correlate well with the logarithm of the molar solubility of water in the media, higher initial rates being observed in the solvents/mixtures with lower water solubilities. The data for the mixtures indicate that ppl apparent activity responds to bulk property of the solvent. Measurements of enzyme particle sizes in five of the solvents, as function of enzyme hydration, revealed that mean particle sizes increased with enzyme hydration in all the solvents, differences between solvents being more pronounced at enzyme hydration levels close to 10%. At this hydration level, solvents having a higher water content lead to lower reaction rates; these are the solvents where the mean enzyme particle sizes are greater. Calculation of the observable modulus indicates there are no internal diffusion limitations. The observed correlation between changes in initial rates and changes in external surface area of the enzyme particles suggests that interfacial activation of ppl is only effective at the external surface of the particles. Data obtained for the mixtures indicate that ppl enantioselectivity depends on specific solvent-enzyme interactions. We make reference to ppl hydration and activity in supercritical carbon dioxide.

  10. Preparation and application of zirconium sulfate supported on SAPO-34 molecular sieve as solid acid catalyst for esterification

    SciTech Connect

    Xu, Dongyan Ma, Hong; Cheng, Fei

    2014-05-01

    Graphical abstract: - Highlights: • SAPO-34 supported zirconium sulfate solid acid catalyst was prepared. • Esterification of acetic acid with ethanol can be catalyzed by ZS/SAPO-34. • The hydration of ZS is vital to the acidic property and catalytic performance. • The ZS/SAPO-34 catalyst treated at 200 °C shows good reusability. - Abstract: Zirconium sulfate (ZS) was supported on SAPO-34 molecular sieve by using an incipient wetness impregnation method with zirconium sulfate as the precursor. The as-prepared catalysts were used as solid acid catalyst for esterification reaction of acetic acid with ethanol. The influence of calcination temperature on the acidic property, catalytic activity, and reusability of ZS/SAPO-34 catalysts were mainly investigated. FT-IR, SEM, EDS and TG analysis have been carried out to demonstrate the characteristics of ZS/SAPO-34 catalysts. It was found that the 30 wt%ZS/SAPO-34 catalysts display the property of superacid irrespective of calcination temperature. The ZS/SAPO-34 catalyst treated at 200 °C can enhance the interaction between the supported ZS and SAPO-34 and keep the catalyst remaining substantially active after several reaction cycles. However, further increasing calcination temperature will cause the transfer of ZS from hydrate to anhydrous phase, and thus the decrease of activity.

  11. Kinetics of acid base catalyzed transesterification of Jatropha curcas oil.

    PubMed

    Jain, Siddharth; Sharma, M P

    2010-10-01

    Out of various non-edible oil resources, Jatropha curcas oil (JCO) is considered as future feedstock for biodiesel production in India. Limited work is reported on the kinetics of transesterification of high free fatty acids containing oil. The present study reports the results of kinetic study of two-step acid base catalyzed transesterification process carried out at an optimum temperature of 65 °C and 50 °C for esterification and transesterification respectively under the optimum methanol to oil ratio of 3:7 (v/v), catalyst concentration 1% (w/w) for H₂SO₄ and NaOH. The yield of methyl ester (ME) has been used to study the effect of different parameters. The results indicate that both esterification and transesterification reaction are of first order with reaction rate constant of 0.0031 min⁻¹ and 0.008 min⁻¹ respectively. The maximum yield of 21.2% of ME during esterification and 90.1% from transesterification of pretreated JCO has been obtained.

  12. Efficient bifunctional catalyst lipase/organophosphonic acid-functionalized silica for biodiesel synthesis by esterification of oleic acid with ethanol.

    PubMed

    Yin, Ping; Chen, Wen; Liu, Wei; Chen, Hou; Qu, Rongjun; Liu, Xiguang; Tang, Qinghua; Xu, Qiang

    2013-07-01

    An efficient bifunctional catalyst lipase/organophosphonic acid-functionalized silica (SG-T-P-LS) has been successfully developed, and biodiesel production of fatty acid ethyl ester (FAEE) from free fatty acid (FFA) oleic acid with short-chain alcohol ethanol catalyzed by SG-T-P-LS was investigated. The process optimization using response surface methodology (RSM) was performed and the interactions between the operational variables were elucidated, and it was found that the molar ratio of alcohol to acid was the most significant factor. The optimum values for maximum conversion ratio can be obtained by using a Box-Behnken center-united design, and the conversion ratio could reach 89.94 ± 0.42% under the conditions that ethanol/acid molar ratio was 1.05:1 and SG-T-P-LS to FFA weight ratio was 14.9 wt.% at 28.6°C. The research results show that SG-T-P and LS-20 could work cooperatively to promote the esterification reaction, and the bifunctional catalyst SG-T-P-LS is a potential catalyst for biodiesel production.

  13. Metaloxide--ZrO2 catalysts for the esterification and transesterification of free fatty acids and triglycerides to obtain bio-diesel

    DOEpatents

    Kim, Manhoe; Salley, Steven O.; Ng, K. Y. Simon

    2016-09-06

    Mixed metal oxide catalysts (ZnO, CeO, La2O3, NiO, Al203, SiO2, TiO2, Nd2O3, Yb2O3, or any combination of these) supported on zirconia (ZrO2) or hydrous zirconia are provided. These mixed metal oxide catalysts can be prepared via coprecipitation, impregnation, or sol-gel methods from metal salt precursors with/without a Zirconium salt precursor. Metal oxides/ZrO2 catalyzes both esterification and transesterification of oil containing free fatty acids in one batch or in single stage. In particular, these mixed metal oxides supported or added on zirconium oxide exhibit good activity and selectivity for esterification and transesterification. The low acid strength of this catalyst can avoid undesirable side reaction such as alcohol dehydration or cracking of fatty acids. Metal oxides/ZrO2 catalysts are not sensitive to any water generated from esterification. Thus, esterification does not require a water free condition or the presence of excess methanol to occur when using the mixed metal oxide catalyst. The FAME yield obtained with metal oxides/ZrO2 is higher than that obtained with homogeneous sulfuric acid catalyst. Metal oxides/ZrO2 catalasts can be prepared as strong pellets and in various shapes for use directly in a flow reactor. Furthermore, the pellet has a strong resistance toward dissolution to aqueous or oil phases.

  14. Characterization of the esterification reaction in high free fatty acid oils

    NASA Astrophysics Data System (ADS)

    Altic, Lucas Eli Porter

    Energy and vegetable oil prices have caused many biodiesel producers to turn to waste cooking oils as feedstocks. These oils contain high levels of free fatty acids (FFAs) which make them difficult or impossible to convert to biodiesel by conventional production methods. Esterification is required for ultra-high FFA feedstocks such as Brown Grease. In addition, ultrasonic irradiation has the potential to improve the kinetics of the esterification reaction. 2-level, multi-factor DOE experiments were conducted to characterize the esterification reaction in ultra-high FFA oils as well as determine whether ultrasonic irradiation gives any benefit besides energy input. The study determined that sulfuric acid content had the greatest effect followed by temperature and water content (inhibited reaction). Methanol content had no effect in the range studied. A small interaction term existed between sulfuric acid and temperature. The study also concluded that sonication did not give any additional benefit over energy input.

  15. Simultaneous Clostridial fermentation, lipase-catalyzed esterification, and ester extraction to enrich diesel with butyl butyrate.

    PubMed

    van den Berg, Corjan; Heeres, Arjan S; van der Wielen, Luuk A M; Straathof, Adrie J J

    2013-01-01

    The recovery of 1-butanol from fermentation broth is energy-intensive since typical concentrations in fermentation broth are below 20 g L(-1). To prevent butanol inhibition and high downstream processing costs, we aimed at producing butyl esters instead of 1-butanol. It is shown that it is possible to perform simultaneously clostridial fermentation, esterification of the formed butanol to butyl butyrate, and extraction of this ester by hexadecane. The very high partition coefficient of butyl butyrate pulls the esterification towards the product side even at fermentation pH and relatively low butanol concentrations. The hexadecane extractant is a model diesel compound and is nontoxic to the cells. If butyl butyrate enriched diesel can directly be used as car fuel, no product recovery is required. A proof-of-principle experiment for the one-pot bio-ester production from glucose led to 5 g L(-1) butyl butyrate in the hexadecane phase. The principle may be extended to a wide range of esters, especially to longer chain ones.

  16. Simultaneous Clostridial fermentation, lipase-catalyzed esterification, and ester extraction to enrich diesel with butyl butyrate.

    PubMed

    van den Berg, Corjan; Heeres, Arjan S; van der Wielen, Luuk A M; Straathof, Adrie J J

    2013-01-01

    The recovery of 1-butanol from fermentation broth is energy-intensive since typical concentrations in fermentation broth are below 20 g L(-1). To prevent butanol inhibition and high downstream processing costs, we aimed at producing butyl esters instead of 1-butanol. It is shown that it is possible to perform simultaneously clostridial fermentation, esterification of the formed butanol to butyl butyrate, and extraction of this ester by hexadecane. The very high partition coefficient of butyl butyrate pulls the esterification towards the product side even at fermentation pH and relatively low butanol concentrations. The hexadecane extractant is a model diesel compound and is nontoxic to the cells. If butyl butyrate enriched diesel can directly be used as car fuel, no product recovery is required. A proof-of-principle experiment for the one-pot bio-ester production from glucose led to 5 g L(-1) butyl butyrate in the hexadecane phase. The principle may be extended to a wide range of esters, especially to longer chain ones. PMID:22833369

  17. Two-step synthesis of fatty acid ethyl ester from soybean oil catalyzed by Yarrowia lipolytica lipase

    PubMed Central

    2011-01-01

    Background Enzymatic biodiesel production by transesterification in solvent media has been investigated intensively, but glycerol, as a by-product, could block the immobilized enzyme and excess n-hexane, as a solution aid, would reduce the productivity of the enzyme. Esterification, a solvent-free and no-glycerol-release system for biodiesel production, has been developed, and two-step catalysis of soybean oil, hydrolysis followed by esterification, with Yarrowia lipolytica lipase is reported in this paper. Results First, soybean oil was hydrolyzed at 40°C by 100 U of lipase broth per 1 g of oil with approximately 30% to 60% (vol/vol) water. The free fatty acid (FFA) distilled from this hydrolysis mixture was used for the esterification of FFA to fatty acid ethyl ester by immobilized lipase. A mixture of 2.82 g of FFA and equimolar ethanol (addition in three steps) were shaken at 30°C with 18 U of lipase per 1 gram of FFA. The degree of esterification reached 85% after 3 hours. The lipase membranes were taken out, dehydrated and subjected to fresh esterification so that over 82% of esterification was maintained, even though the esterification was repeated every 3 hours for 25 batches. Conclusion The two-step enzymatic process without glycerol released and solvent-free demonstrated higher efficiency and safety than enzymatic transesterification, which seems very promising for lipase-catalyzed, large-scale production of biodiesel, especially from high acid value waste oil. PMID:21366905

  18. Zn(OTf)2-promoted chemoselective esterification of hydroxyl group bearing carboxylic acids.

    PubMed

    Mamidi, Narsimha; Manna, Debasis

    2013-03-15

    Selective esterification of aliphatic and aromatic carboxylic acids with various alcohols is studied using triphenylphosphine, I2, and a catalytic amount of Zn(OTf)2. Use of this catalyst allows the formation of esters at a faster rate with good to excellent yield by activating the in situ generated acyloxyphosphonium ion intermediate. During the esterification process, both their aromatic and aliphatic hydroxyl groups are fully preserved from transesterification. The results show that the bulkiness and the reactivity of this doubly activated intermediate III control the selectivity and the rate of the reaction, respectively. The method is also useful for direct amidation reactions.

  19. Esterification and Transesterification of greases to fatty acid methyl esters with highly active diphenylamine salts

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Diphenylamine sulfate (DPAS) and diphenylamine hydrochloride (DPACl) salts were found to be highly active catalysts for esterification and transesterification of inexpensive greases to fatty acid methyl esters (FAME). In the presence of catalytic amounts of DPAS or DPACl and excess methanol, the fr...

  20. Ultrasound-Assisted Enantioselective Esterification of Ibuprofen Catalyzed by a Flower-Like Nanobioreactor.

    PubMed

    An, Baiyi; Fan, Hailin; Wu, Zhuofu; Zheng, Lu; Wang, Lei; Wang, Zhi; Chen, Guang

    2016-01-01

    A flower-like nanobioreactor was prepared for resolution of ibuprofen in organic solvents. Ultrasound irradiation has been used to improve the enzyme performance of APE1547 (a thermophilic esterase from the archaeon Aeropyrum pernix K1) in the enantioselective esterification. Under optimum reaction conditions (ultrasound power, 225 W; temperature, 45 °C; water activity, 0.21), the immobilized APE1547 showed an excellent catalytic performance (enzyme activity, 13.26 μmol/h/mg; E value, 147.1). After ten repeated reaction batches, the nanobioreactor retained almost 100% of its initial enzyme activity and enantioselectivity. These results indicated that the combination of the immobilization method and ultrasound irradiation can enhance the enzyme performance dramatically. PMID:27136511

  1. Lipase-catalyzed process in an anhydrous medium with enzyme reutilization to produce biodiesel with low acid value.

    PubMed

    Azócar, Laura; Ciudad, Gustavo; Heipieper, Hermann J; Muñoz, Robinson; Navia, Rodrigo

    2011-12-01

    One major problem in the lipase-catalyzed production of biodiesel or fatty acid methyl esters (FAME) is the high acidity of the product, mainly caused by water presence, which produces parallel hydrolysis and esterification reactions instead of transesterification to FAME. Therefore, the use of reaction medium in absence of water (anhydrous medium) was investigated in a lipase-catalyzed process to improve FAME yield and final product quality. FAME production catalyzed by Novozym 435 was carried out using waste frying oil (WFO) as raw material, methanol as acyl acceptor, and 3Å molecular sieves to extract the water. The anhydrous conditions allowed the esterification of free fatty acids (FFA) from feedstock at the initial reaction time. However, after the initial esterification process, water absence avoided the consecutives reactions of hydrolysis and esterification, producing FAME mainly by transesterification. Using this anhydrous medium, a decreasing in both the acid value and the diglycerides content in the product were observed, simultaneously improving FAME yield. Enzyme reuse in the anhydrous medium was also studied. The use of the moderate polar solvent tert-butanol as a co-solvent led to a stable catalysis using Novozym 435 even after 17 successive cycles of FAME production under anhydrous conditions. These results indicate that a lipase-catalyzed process in an anhydrous medium coupled with enzyme reuse would be suitable for biodiesel production, promoting the use of oils of different origin as raw materials.

  2. Effects of citric acid esterification on digestibility, structural and physicochemical properties of cassava starch.

    PubMed

    Mei, Ji-Qiang; Zhou, Da-Nian; Jin, Zheng-Yu; Xu, Xue-Ming; Chen, Han-Qing

    2015-11-15

    In this study, citric acid was used to react with cassava starch in order to compare the digestibility, structural and physicochemical properties of citrate starch samples. The results indicated that citric acid esterification treatment significantly increased the content of resistant starch (RS) in starch samples. The swelling power and solubility of citrate starch samples were lower than those of native starch. Compared with native starch, a new peak at 1724 cm(-1) was appeared in all citrate starch samples, and crystalline peaks of all starch citrates became much smaller or even disappeared. Differential scanning calorimetry results indicated that the endothermic peak of citrate starches gradually shrank or even disappeared. Moreover, the citrate starch gels exhibited better freeze-thaw stability. These results suggested that citric acid esterification induced structural changes in cassava starch significantly affected its digestibility and it could be a potential method for the preparation of RS with thermal stability.

  3. Microwave-assisted biodiesel production by esterification of palm fatty acid distillate.

    PubMed

    Lokman, Ibrahim M; Rashid, Umer; Zainal, Zulkarnain; Yunus, Robiah; Taufiq-Yap, Yun Hin

    2014-01-01

    In the current research work, effect of microwave irradiation energy on the esterification of palm fatty acid distillate (PFAD) to produce PFAD methyl ester / biodiesel was intensively appraised. The PFAD is a by-product from refinery of crude palm oil consisting >85% of free fatty acid (FFA). The esterification reaction process with acid catalyst is needed to convert the FFA into fatty acid methyl ester or known as biodiesel. In this work, fabricated microwave-pulse width modulation (MPWM) reactor with controlled temperature was designed to be capable to increase the PFAD biodiesel production rate. The classical optimization technique was used in order to study the relationship and the optimum condition of variables involved. Consequently, by using MPWM reactor, mixture of methanol-to-PFAD molar ratio of 9:1, 1 wt.% of sulfuric acid catalyst, at 55°C reaction temperature within 15 min reaction time gave 99.5% of FFA conversion. The quality assessment and properties of the product were analyzed according to the American Society for Testing and Materials (ASTM), European (EN) standard methods and all results were in agreement with the standard requirements. It revealed that the use of fabricated MPWM with controlled temperature was significantly affecting the rate of esterification reaction and also increased the production yield of PFAD methyl ester.

  4. Protic acid immobilized on solid support as an extremely efficient recyclable catalyst system for a direct and atom economical esterification of carboxylic acids with alcohols.

    PubMed

    Chakraborti, Asit K; Singh, Bavneet; Chankeshwara, Sunay V; Patel, Alpesh R

    2009-08-21

    A convenient and clean procedure of esterification is reported by direct condensation of equimolar amounts of carboxylic acids with alcohols catalyzed by an easy to prepare catalyst system of perchloric acid immobilized on silica gel (HClO(4)-SiO(2)). The direct condensation of aryl, heteroaryl, styryl, aryl alkyl, alkyl, cycloalkyl, and long-chain aliphatic carboxylic acids with primary/secondary alkyl/cycloalkyl, allyl, propargyl, and long-chain aliphatic alcohols has been achieved to afford the corresponding esters in excellent yields. Chiral alcohol and N-t-Boc protected chiral amino acid also resulted in ester formation with the representative carboxylic acid or alcohol without competitive N-t-Boc deprotection and detrimental effect on the optical purity of the product demonstrating the mildness and chemoselectivity of the procedure. The esters of long-chain (>C(10)) acids and alcohols are obtained in high yields. The catalyst is recovered and recycled without significant loss of activity. The industrial application of the esterification process is demonstrated by the synthesis of prodrugs of ibuprofen and a few commercial flavoring agents. Other protic acids such as H(2)SO(4), HBr, TfOH, HBF(4), and TFA that were adsorbed on silica gel were less effective compared to HClO(4)-SiO(2) following the order HClO(4)-SiO(2) > H(2)SO(4)-SiO(2) > HBr-SiO(2) > TfOH-SiO(2) > HBF(4)-SiO(2) approximately TFA-SiO(2). When HClO(4) was immobilized on other solid supports the catalytic efficiency followed the order HClO(4)-SiO(2) > HClO(4)-K10 > HClO(4)-Al(2)O(3) (neutral) > HClO(4)-Al(2)O(3) (acidic) > HClO(4)-Al(2)O(3) (basic).

  5. Direct esterification of ammonium salts of carboxylic acids

    SciTech Connect

    Halpern, Yuval

    2003-06-24

    A non-catalytic process for producing esters, the process comprising reacting an ammonium salt of a carboxylic acid with an alcohol and removing ammonia from the reaction mixture. Selectivities for the desired ester product can exceed 95 percent.

  6. Enhanced esterification of oleic acid and methanol by deep eutectic solvent assisted Amberlyst heterogeneous catalyst.

    PubMed

    Pan, Ying; Alam, Md Asraful; Wang, Zhongming; Wu, Jingcheng; Zhang, Yi; Yuan, Zhenhong

    2016-11-01

    In present study, esterification of oleic acid with methanol using deep eutectic solvent (DES) assisted Amberlyst heterogeneous catalyst was investigated to produce biodiesel. Results showed that esterification efficiency was enhanced by the DES. The combined effect of DES on Amberlyst BD20 (BD20) is better than Amberlyst 15 (A-15) due to different structure. The optimal reaction conditions were 12:1M ratio of methanol to oleic acid, 20%(wt/wt) catalyst (BD20-DES (2:8) and A-15-DES (8:2)) at 85°C for 100min with agitating at 200rpm. The mechanism involved in catalysis and their capacity to reuse were studied. We proposed, Choline chloride-glycerol (Chcl-gly) DES could enhance the Amberlyst function due to the hydrogen bond effect on both DES and water. BD20 has fewer pores than A-15, have desirable performance in decreasing the inhibition the water during esterification of high FFA content and provide better performance in reuse.

  7. Enhanced esterification of oleic acid and methanol by deep eutectic solvent assisted Amberlyst heterogeneous catalyst.

    PubMed

    Pan, Ying; Alam, Md Asraful; Wang, Zhongming; Wu, Jingcheng; Zhang, Yi; Yuan, Zhenhong

    2016-11-01

    In present study, esterification of oleic acid with methanol using deep eutectic solvent (DES) assisted Amberlyst heterogeneous catalyst was investigated to produce biodiesel. Results showed that esterification efficiency was enhanced by the DES. The combined effect of DES on Amberlyst BD20 (BD20) is better than Amberlyst 15 (A-15) due to different structure. The optimal reaction conditions were 12:1M ratio of methanol to oleic acid, 20%(wt/wt) catalyst (BD20-DES (2:8) and A-15-DES (8:2)) at 85°C for 100min with agitating at 200rpm. The mechanism involved in catalysis and their capacity to reuse were studied. We proposed, Choline chloride-glycerol (Chcl-gly) DES could enhance the Amberlyst function due to the hydrogen bond effect on both DES and water. BD20 has fewer pores than A-15, have desirable performance in decreasing the inhibition the water during esterification of high FFA content and provide better performance in reuse. PMID:27614157

  8. Effect of ethyl esterification of phenolic acids on low-density lipoprotein oxidation.

    PubMed

    Chalas, J; Claise, C; Edeas, M; Messaoudi, C; Vergnes, L; Abella, A; Lindenbaum, A

    2001-02-01

    Inhibition of copper-induced low-density lipoprotein (LDL) oxidation by phenolic acids and their ethyl esters was investigated. LDL oxidation was evaluated by the hydroperoxide concentration and the chromatographic pattern of apoprotein fractions after fast protein liquid chromatography (FPLC). Antiradical properties against 1,1-diphenyl-2-picryl hydrazyl (DPPH) radical and 2,2'-azobis(2-amidinopropane)dihydrochloride (AAPH) were also investigated, and lipophilicity determined by thin-layer chromatography. Caffeic acid at 5 microM and sinapic acid at 10 microM protected LDL against oxidation, inhibiting both hydroperoxide formation and the increase of apoprotein negative charge. Ferulic, gallic and p-hydroxy cinnamic acids were ineffective. Ethyl esterification increased the lipophilicity of the five acids, and enhanced the antioxidant properties of caffeic, sinapic and ferulic acids. Ethyl caffeate was protective at 1 microM. In contrast, gallic and p-hydroxy cinnamic ethyl esters were ineffective. Our results indicate that ethyl esterification of phenolic acids increases lipophilicity of their ethyl esters and may enable a better incorporation into the lipid layer of the LDL particle and the exertion of their antioxidant effect in the true site of lipoperoxidation. However, increasing lipophilicity is not the only mechanism able to potentiate preexisting antioxidant properties of molecules, and probably other mechanisms are implicated.

  9. Production of biodiesel from vegetable oil and microalgae by fatty acid extraction and enzymatic esterification.

    PubMed

    Castillo López, Beatriz; Esteban Cerdán, Luis; Robles Medina, Alfonso; Navarro López, Elvira; Martín Valverde, Lorena; Hita Peña, Estrella; González Moreno, Pedro A; Molina Grima, Emilio

    2015-06-01

    The aim of this work was to obtain biodiesel (methyl esters) from the saponifiable lipids (SLs) fraction of the microalga Nannochloropsis gaditana, whose biomass dry weight contains 12.1 wt% of these lipids. SLs were extracted from the microalga as free fatty acids (FFAs) for subsequent transformation to methyl esters (biodiesel) by enzymatic esterification. Extraction as FFAs rather than as SLs allows them to be obtained with higher purity. Microalgal FFAs were obtained by direct saponification of lipids in the biomass and subsequent extraction-purification with hexane. Esterification of FFAs with methanol was catalysed by lipase Novozym 435 from Candida antarctica. Stability studies of this lipase in the operational conditions showed that the esterification degree (ED) attained with the same batch of lipase remained constant over six reaction cycles (36 h total reaction time). The optimal conditions attained for 4 g of FFAs were 25°C, 200 rpm, methanol/FFA molar ratio of 1.5:1, Novozym 435/FFA ratio of 0.025:1 w/w and 4 h reaction time. In these conditions the ED attained was 92.6%, producing a biodiesel with 83 wt% purity from microalgal FFAs. Several experimental scales were tested (from 4 to 40 g FFAs), and in all cases similar EDs were obtained.

  10. Production of biodiesel from vegetable oil and microalgae by fatty acid extraction and enzymatic esterification.

    PubMed

    Castillo López, Beatriz; Esteban Cerdán, Luis; Robles Medina, Alfonso; Navarro López, Elvira; Martín Valverde, Lorena; Hita Peña, Estrella; González Moreno, Pedro A; Molina Grima, Emilio

    2015-06-01

    The aim of this work was to obtain biodiesel (methyl esters) from the saponifiable lipids (SLs) fraction of the microalga Nannochloropsis gaditana, whose biomass dry weight contains 12.1 wt% of these lipids. SLs were extracted from the microalga as free fatty acids (FFAs) for subsequent transformation to methyl esters (biodiesel) by enzymatic esterification. Extraction as FFAs rather than as SLs allows them to be obtained with higher purity. Microalgal FFAs were obtained by direct saponification of lipids in the biomass and subsequent extraction-purification with hexane. Esterification of FFAs with methanol was catalysed by lipase Novozym 435 from Candida antarctica. Stability studies of this lipase in the operational conditions showed that the esterification degree (ED) attained with the same batch of lipase remained constant over six reaction cycles (36 h total reaction time). The optimal conditions attained for 4 g of FFAs were 25°C, 200 rpm, methanol/FFA molar ratio of 1.5:1, Novozym 435/FFA ratio of 0.025:1 w/w and 4 h reaction time. In these conditions the ED attained was 92.6%, producing a biodiesel with 83 wt% purity from microalgal FFAs. Several experimental scales were tested (from 4 to 40 g FFAs), and in all cases similar EDs were obtained. PMID:25575971

  11. Esterification of fermentation-derived acids via pervaporation

    DOEpatents

    Datta, R.; Tsai, S.P.

    1998-03-03

    A low temperature method for esterifying ammonium- and amine-containing salts is provided whereby the salt is reacted with an alcohol in the presence of heat and a catalyst and then subjected to a dehydration and deamination process using pervaporation. The invention also provides for a method for producing esters of fermentation derived, organic acid salt comprising first cleaving the salt into its cationic part and anionic part, mixing the anionic part with an alcohol to create a mixture; heating the mixture in the presence of a catalyst to create an ester; dehydrating the now heated mixture; and separating the ester from the now-dehydrated mixture. 2 figs.

  12. Esterification of fermentation-derived acids via pervaporation

    DOEpatents

    Datta, Rathin; Tsai, Shih-Perng

    1998-01-01

    A low temperature method for esterifying ammonium- and amine-containing salts is provided whereby the salt is reacted with an alcohol in the presence of heat and a catalyst and then subjected to a dehydration and deamination process using pervaporation. The invention also provides for a method for producing esters of fermentation derived, organic acid salt comprising first cleaving the salt into its cationic part and anionic part, mixing the anionic part with an alcohol to create a mixture; heating the mixture in the presence of a catalyst to create an ester; dehydrating the now heated mixture; and separating the ester from the now-dehydrated mixture.

  13. Computational multiple steady states for enzymatic esterification of ethanol and oleic acid in an isothermal CSTR.

    PubMed

    Ho, Pang-Yen; Chuang, Guo-Syong; Chao, An-Chong; Li, Hsing-Ya

    2005-05-01

    The capacity of complex biochemical reaction networks (consisting of 11 coupled non-linear ordinary differential equations) to show multiple steady states, was investigated. The system involved esterification of ethanol and oleic acid by lipase in an isothermal continuous stirred tank reactor (CSTR). The Deficiency One Algorithm and the Subnetwork Analysis were applied to determine the steady state multiplicity. A set of rate constants and two corresponding steady states are computed. The phenomena of bistability, hysteresis and bifurcation are discussed. Moreover, the capacity of steady state multiplicity is extended to the family of the studied reaction networks.

  14. Biodiesel production by combined fatty acids separation and subsequently enzymatic esterification to improve the low temperature properties.

    PubMed

    Wang, Meng; Nie, Kaili; Cao, Hao; Deng, Li; Wang, Fang; Tan, Tianwei

    2014-12-01

    The poor low-temperature properties of biodiesel, which provokes easy crystallization at low temperature, can cause fuel line plugging and limits its blending amount with petro-diesel. This work aimed to study the production of biodiesel with a new process of improving the low temperature performance of biodiesel. Waste cooking oil was first hydrolyzed into fatty acids (FAs) by 60g immobilized lipase and 240g RO water in 15h. Then, urea complexation was used to divide the FAs into saturated and unsaturated components. The conditions for complexation were: FA-to-urea ratio 1:2 (w/w), methanol to FA ratio 5:1 (v/v), duration 2h. The saturated and unsaturated FAs were then converted to iso-propyl and methyl esters by lipase, respectively. Finally, the esters were mixed together. The CFPP of this mixture was decreased from 5°C to -3°C. Hydrolysis, urea complexation and enzymic catalyzed esterification processes are discussed in this paper. PMID:25441717

  15. Extraction and Esterification of Low-Titer Short-Chain Volatile Fatty Acids from Anaerobic Fermentation with Ionic Liquids.

    PubMed

    Andersen, Stephen J; Berton, Jan K E T; Naert, Pieter; Gildemyn, Sylvia; Rabaey, Korneel; Stevens, Christian V

    2016-08-23

    Ionic liquids can both act as a solvent and mediate esterification to valorize low-titer volatile fatty acids and generate organic solvents from renewable carbon sources including biowaste and CO2 . In this study, four phosphonium ionic liquids were tested for single-stage extraction of acetic acid from a dilute stream and esterification to ethyl acetate with added ethanol and heat. The esterification proceeded with a maximum conversion of 85.9±1.3 % after 30 min at 75 °C at a 1:1 stoichiometric ratio of reactants. Extraction and esterification can be tailored using mixed-anion ionic liquids; this is demonstrated herein using a common trihexyl(tetradecyl)phosphonium cation and a mixed chloride and bis(trifluoromethylsulfonyl)imide anion ionic liquid. As a further proof-of-concept, ethyl acetate was generated from an ionic liquid-driven esterification of an acetic acid extractant generated using CO2 as the only carbon source by microbial electrosynthesis.

  16. Extraction and Esterification of Low-Titer Short-Chain Volatile Fatty Acids from Anaerobic Fermentation with Ionic Liquids.

    PubMed

    Andersen, Stephen J; Berton, Jan K E T; Naert, Pieter; Gildemyn, Sylvia; Rabaey, Korneel; Stevens, Christian V

    2016-08-23

    Ionic liquids can both act as a solvent and mediate esterification to valorize low-titer volatile fatty acids and generate organic solvents from renewable carbon sources including biowaste and CO2 . In this study, four phosphonium ionic liquids were tested for single-stage extraction of acetic acid from a dilute stream and esterification to ethyl acetate with added ethanol and heat. The esterification proceeded with a maximum conversion of 85.9±1.3 % after 30 min at 75 °C at a 1:1 stoichiometric ratio of reactants. Extraction and esterification can be tailored using mixed-anion ionic liquids; this is demonstrated herein using a common trihexyl(tetradecyl)phosphonium cation and a mixed chloride and bis(trifluoromethylsulfonyl)imide anion ionic liquid. As a further proof-of-concept, ethyl acetate was generated from an ionic liquid-driven esterification of an acetic acid extractant generated using CO2 as the only carbon source by microbial electrosynthesis. PMID:27390131

  17. Fascinating and challenging role of tungstate promoted vanadium phosphate towards solvent free esterification of oleic acid.

    PubMed

    Behera, Gobinda Chandra; Parida, K M

    2012-01-28

    A novel solid acid catalyst has been extensively used for the esterification reaction. Herein, tungstate promoted vanadium phosphate material is fabricated from its precursor, VOHPO(4)·0.5H(2)O and its catalytic activities and structure are investigated in detail. This kind of catalyst is, for the first time, applied for the effective production of biodiesel from fatty acids. Although vanadium phosphate has been extensively used in gas phase oxidation reactions, it has not drawn much attention for its application in liquid phase reactions. Our recent results indicate that vanadium phosphate is an effective, minimally polluting and re-usable catalyst that is highly suited to the production of biodiesel from fatty acids. This work extends the possibility of using VPO in other liquid phase reactions.

  18. Kinetics of Ethyl Acetate Synthesis Catalyzed by Acidic Resins

    ERIC Educational Resources Information Center

    Antunes, Bruno M.; Cardoso, Simao P.; Silva, Carlos M.; Portugal, Ines

    2011-01-01

    A low-cost experiment to carry out the second-order reversible reaction of acetic acid esterification with ethanol to produce ethyl acetate is presented to illustrate concepts of kinetics and reactor modeling. The reaction is performed in a batch reactor, and the acetic acid concentration is measured by acid-base titration versus time. The…

  19. Kinetic study on microwave-assisted esterification of free fatty acids derived from Ceiba pentandra Seed Oil.

    PubMed

    Lieu, Thanh; Yusup, Suzana; Moniruzzaman, Muhammad

    2016-07-01

    Recently, a great attention has been paid to advanced microwave technology that can be used to markedly enhance the biodiesel production process. Ceiba pentandra Seed Oil containing high free fatty acids (FFA) was utilized as a non-edible feedstock for biodiesel production. Microwave-assisted esterification pretreatment was conducted to reduce the FFA content for promoting a high-quality product in the next step. At optimum condition, the conversion was achieved 94.43% using 2wt% of sulfuric acid as catalyst where as 20.83% conversion was attained without catalyst. The kinetics of this esterification reaction was also studied to determine the influence of factors on the rate of reaction and reaction mechanisms. The results indicated that microwave-assisted esterification was of endothermic second-order reaction with the activation energy of 53.717kJ/mol. PMID:27019128

  20. Kinetic study on microwave-assisted esterification of free fatty acids derived from Ceiba pentandra Seed Oil.

    PubMed

    Lieu, Thanh; Yusup, Suzana; Moniruzzaman, Muhammad

    2016-07-01

    Recently, a great attention has been paid to advanced microwave technology that can be used to markedly enhance the biodiesel production process. Ceiba pentandra Seed Oil containing high free fatty acids (FFA) was utilized as a non-edible feedstock for biodiesel production. Microwave-assisted esterification pretreatment was conducted to reduce the FFA content for promoting a high-quality product in the next step. At optimum condition, the conversion was achieved 94.43% using 2wt% of sulfuric acid as catalyst where as 20.83% conversion was attained without catalyst. The kinetics of this esterification reaction was also studied to determine the influence of factors on the rate of reaction and reaction mechanisms. The results indicated that microwave-assisted esterification was of endothermic second-order reaction with the activation energy of 53.717kJ/mol.

  1. Lipophilisation of Caffeic Acid through Esterification with Propanol Using Water-tolerable Acidic Ionic Liquid as Catalyst.

    PubMed

    Liu, Wei; Han, Liya

    2015-01-01

    Propyl caffeate was synthesized to produce lipophilic antioxidant, which used caffeic acid and propanol as starting materials, acidic ionic liquid as catalyst. The highest yield of propyl caffeate (98.7±0.8%) have been achieved under the optimum as follows: 1-butylsulfonic-3-methylimidazolium tosylate showed the best catalytic performance, molar ratio of caffeic acid to propanol was 1:20, reaction temperature was 90°C and the amount of acidic ionic liquid was 40%. The relationship between temperature and the forward rate constant gave the activation energy of 33.6 kJ mol(-1), which indicated that acidic ionic liquid possesses high catalytic activity in the synthesis of PC. And the activity of acidic ionic liquid was not inhibited by the water produced during the esterification process. More importantly, this reaction system can even proceed smoothly when initial water content was 5%.

  2. Comprehensive kinetic studies of acidic oil continuous esterification by cation-exchange resin in fixed bed reactors.

    PubMed

    Cheng, Yu; Feng, Yaohui; Ren, Yanbiao; Liu, Xuan; Gao, Aoran; He, Benqiao; Yan, Feng; Li, Jianxin

    2012-06-01

    Biodiesel produced by esterification from molar ratio of methanol to free fatty acid (FFA) as 25:1 in presence of triglyceride was carried out with cation-exchange resin as a heterogeneous catalyst in three different scales of fixed bed reactors from minireactor (6.8 mm × 110 mm) to pilot scale reactor (70 mm × 1260 mm) at 338 K. The kinetic study of esterification was undertaken in terms of pseudo-homogeneous mechanism and performed as a first order reaction with elimination of the solid-liquid internal and external mass transfer resistances. Moreover, a kinetic model of FFA esterification was developed to illustrate the relationship between the FFA conversion and the catalyst bed height of fixed bed reactor. The model was also suitable for various resins in fixed bed reactor. The theoretical predictions were in agreement with the experimental data with root mean square (RMS) errors <10.

  3. Preparation and characterization of biomass carbon-based solid acid catalyst for the esterification of oleic acid with methanol.

    PubMed

    Liu, Tiantian; Li, Zhilong; Li, Wei; Shi, Congjiao; Wang, Yun

    2013-04-01

    A solid acid catalyst, prepared by sulfonating carbonized corn straw, was proved to be an efficient and environmental benign catalyst for the esterification of oleic acid and methanol. Various synthetic parameters, such as carbonization temperature and time were systematically examined. It was found that the catalyst exhibited the highest acid density of 2.64 mmol/g by NaOH titration. A quantitative yield (98%) of ester was achieved, using the most active sulfonated catalyst at 333 K with a 7 wt.% catalyst/oleic acid ratio for 4h, at a 7:1 M ratio of methanol/oleic acid, while the commercial available Amberlyst-15 only gave 85% yield under the same reaction condition.

  4. Mesoporous Silica-Supported Diarylammonium Catalysts for Esterification of Free Fatty Acids in Greases

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Biodiesel, typically fatty acid methyl esters (FAME), has received much attention because it is a renewable biofuel that contributes little to global warming compared to petroleum-based diesel fuel. The most common method used for biodiesel production is based on the alkali-catalyzed transesterific...

  5. Reaction kinetics of free fatty acids esterification in palm fatty acid distillate using coconut shell biochar sulfonated catalyst

    NASA Astrophysics Data System (ADS)

    Hidayat, Arif; Rochmadi, Wijaya, Karna; Budiman, Arief

    2015-12-01

    Recently, a new strategy of preparing novel carbon-based solid acids has been developed. In this research, the esterification reactions of Palm Fatty Acid Distillate (PFAD) with methanol, using coconut shell biochar sulfonated catalyst from biomass wastes as catalyst, were studied. In this study, the coconut shell biochar sulfonated catalysts were synthesized by sulfonating the coconut shell biochar using concentrated H2SO4. The kinetics of free fatty acid (FFA) esterification in PFAD using a coconut shell biochar sulfonated catalyst was also studied. The effects of the mass ratio of catalyst to oil (1-10%), the molar ratio of methanol to oil (6:1-12:1), and the reaction temperature (40-60°C) were studied for the conversion of PFAD to optimize the reaction conditions. The results showed that the optimal conditions were an methanol to PFAD molar ratio of 12:1, the amount of catalyst of 10%w, and reaction temperature of 60°C. The proposed kinetic model shows a reversible second order reaction and represents all the experimental data satisfactorily, providing deeper insight into the kinetics of the reaction.

  6. Preparation and Characterization of Sulfonic Acid Functionalized Silica and Its Application for the Esterification of Ethanol and Maleic Acid

    NASA Astrophysics Data System (ADS)

    Sirsam, Rajkumar; Usmani, Ghayas

    2016-04-01

    The surface of commercially available silica gel, 60-200 mesh size, was modified with sulfonic acid through surface activation, grafting of 3-Mercaptopropyltrimethoxysilane, oxidation and acidification of 3-Mercaptopropylsilica. Sulfonic Acid Functionalization of Silica (SAFS) was confirmed by Fourier Transform Infra-red (FTIR) spectroscopy and thermal gravimetric analysis. Acid-base titration was used to estimate the cation exchange capacity of the SAFS. Catalytic activity of SAFS was judged for the esterification of ethanol with maleic acid. An effect of different process parameters viz. molar ratio, catalyst loading, speed of agitation and temperature were studied and optimized by Box Behnken Design (BBD) of Response Surface Methodology (RSM). Quadratic model developed by BBD-RSM reasonably satisfied an experimental and predicted values with correlation coefficient value R2 = 0.9504.

  7. Efficient mono-acylation of fructose by lipase-catalyzed esterification in ionic liquid co-solvents.

    PubMed

    Li, Lu; Ji, Fangling; Wang, Jingyun; Jiang, Bo; Li, Yachen; Bao, Yongming

    2015-10-30

    Fructose monoesters are eco-friendly nonionic surfactants in various applications. Selective preparation of mono-acylated fructose is challenging due to the multiple hydroxyl sites available for acylation both chemically and enzymatically. Ionic liquids (ILs) have profound impacts not only on the reaction media but also on the catalytic properties of enzymes in the acylation process. In this study, utilizing an IL co-solvent system, selective synthesis of mono-acylated fructose with lauric acid catalyzed by immobilized Candida antarctica lipase B (CALB) was investigated. The imidazolium-based ILs selected as co-solvents with 2-methyl-2-butanol (2M2B) markedly improved the ratios of monolauroyl fructose in the presence of 60% [BMIM][TfO] (v/v) and 20% [BMIM][BF4] (v/v), in which the mono-acylated fructose was 85% and 78% respectively. Based on a Ping-Pong Bi-Bi model, a kinetic equation was fitted, by which the kinetic parameters revealed that the affinity between fructose and acyl-enzyme intermediate was enhanced. The inhibition effect of fructose on free enzyme was weakened in the presence of IL co-solvents. The conformation of CALB binding substrates also changed in the co-solvent system as demonstrated by Fourier transform infrared spectra. These results demonstrated that the variation of CALB kinetic characteristics was a crucial factor for the selectivity of mono-acylation in ILs/2M2B co-solvents.

  8. Efficient mono-acylation of fructose by lipase-catalyzed esterification in ionic liquid co-solvents.

    PubMed

    Li, Lu; Ji, Fangling; Wang, Jingyun; Jiang, Bo; Li, Yachen; Bao, Yongming

    2015-10-30

    Fructose monoesters are eco-friendly nonionic surfactants in various applications. Selective preparation of mono-acylated fructose is challenging due to the multiple hydroxyl sites available for acylation both chemically and enzymatically. Ionic liquids (ILs) have profound impacts not only on the reaction media but also on the catalytic properties of enzymes in the acylation process. In this study, utilizing an IL co-solvent system, selective synthesis of mono-acylated fructose with lauric acid catalyzed by immobilized Candida antarctica lipase B (CALB) was investigated. The imidazolium-based ILs selected as co-solvents with 2-methyl-2-butanol (2M2B) markedly improved the ratios of monolauroyl fructose in the presence of 60% [BMIM][TfO] (v/v) and 20% [BMIM][BF4] (v/v), in which the mono-acylated fructose was 85% and 78% respectively. Based on a Ping-Pong Bi-Bi model, a kinetic equation was fitted, by which the kinetic parameters revealed that the affinity between fructose and acyl-enzyme intermediate was enhanced. The inhibition effect of fructose on free enzyme was weakened in the presence of IL co-solvents. The conformation of CALB binding substrates also changed in the co-solvent system as demonstrated by Fourier transform infrared spectra. These results demonstrated that the variation of CALB kinetic characteristics was a crucial factor for the selectivity of mono-acylation in ILs/2M2B co-solvents. PMID:26343327

  9. Improvement of pro-oxidant capacity of protocatechuic acid by esterification.

    PubMed

    Zeraik, Maria Luiza; Petrônio, Maicon S; Coelho, Dyovani; Regasini, Luis Octavio; Silva, Dulce H S; da Fonseca, Luiz Marcos; Machado, Sergio A S; Bolzani, Vanderlan S; Ximenes, Valdecir F

    2014-01-01

    Pro-oxidant effects of phenolic compounds are usually correlated to the one-electron redox potential of the phenoxyl radicals. Here we demonstrated that, besides their oxidizability, hydrophobicity can also be a decisive factor. We found that esterification of protocatechuic acid (P0) provoked a profound influence in its pro-oxidant capacity. The esters bearing alkyl chains containing two (P2), four (P4) and seven (P7) carbons, but not the acid precursor (P0), were able to exacerbate the oxidation of trolox, α-tocopherol and rifampicin. This effect was also dependent on the catechol moiety, since neither gallic acid nor butyl gallate showed any pro-oxidant effects. A comparison was also made with apocynin, which is well-characterized regarding its pro-oxidant properties. P7 was more efficient than apocynin regarding co-oxidation of trolox. However, P7 was not able to co-oxidize glutathione and NADH, which are targets of the apocynin radical. A correlation was found between pro-oxidant capacity and the stability of the radicals, as suggested by the intensity of the peak current in the differential pulse voltammetry experiments. In conclusion, taking into account that hydroquinone and related moieties are frequently found in biomolecules and quinone-based chemotherapeutics, our demonstration that esters of protocatechuic acid are specific and potent co-catalysts in their oxidations may be very relevant as a pathway to exacerbate redox cycling reactions, which are usually involved in their biological and pharmacological mechanisms of action.

  10. Increased hepatic cholesterol esterification with essential fatty acid deficiency (EFAD): relationship to plasma lipoprotein (LP) cholesterol content

    SciTech Connect

    Ney, D.M.; Ziboh, V.A.; Schneeman, B.O.

    1986-03-01

    EFAD in the rat is associated with hepatic accumulation of esterified cholesterol and altered distribution of cholesterol between plasma and hepatic tissue. Little is known regarding the impact of EFAD on LP composition. To determine the relationship between hepatic cholesterol esterification and plasma lP composition in control (C) and EFAD male Wistar rats, the authors induced EFAD with continuous intragastric (IG) infusion of EFA-free solutions containing 3.5% of calories as triolein for 7 and 14 days. C animals received IG infusion of solutions containing 3.5% of calories as linoleic acid. Data in the EFAD groups reveal: (i) marked decreases in hepatic EFAs and increases in monoenoic acids; (ii) progressive increases in hepatic content of triglyceride and esterified cholesterol with 7 and 14 days of feeding; (iii) assay of acyl CoA:cholesterol acyltransferase activity in hepatic tissue using /sup 14/C-cholesterol demonstrates an increase in hepatic cholesterol esterification when compared to C animals. Increased hepatic cholesterol esterification correlates with elevated levels of esterified cholesterol in plasma VLDL and HDL particles. These data indicate that the elevated levels of cholesterol esters in LP particles is due, at least in part, to increased hepatic cholesterol esterification with EFAD.

  11. In-Water and Neat Batch and Continuous-Flow Direct Esterification and Transesterification by a Porous Polymeric Acid Catalyst.

    PubMed

    Baek, Heeyoel; Minakawa, Maki; Yamada, Yoichi M A; Han, Jin Wook; Uozumi, Yasuhiro

    2016-05-18

    A porous phenolsulphonic acid-formaldehyde resin (PAFR) was developed. The heterogeneous catalyst PAFR was applied to the esterification of carboxylic acids and alcohols, affording the carboxylic acid esters in a yield of up to 95% where water was not removed from the reaction mixture. Surprisingly, the esterification in water as a solvent proceeded to afford the desired esters in high yield. PAFR provided the corresponding esters in higher yield than other homogeneous and heterogeneous catalysts. The transesterification of alcohols and esters was also investigated by using PAFR, giving the corresponding esters. PAFR was applied to the batch-wise and continuous-flow production of biodiesel fuel FAME. The PAFR-packed flow reactor that was developed for the synthesis of carboxylic acids and FAME worked for four days without loss of its catalytic activity.

  12. In-Water and Neat Batch and Continuous-Flow Direct Esterification and Transesterification by a Porous Polymeric Acid Catalyst.

    PubMed

    Baek, Heeyoel; Minakawa, Maki; Yamada, Yoichi M A; Han, Jin Wook; Uozumi, Yasuhiro

    2016-01-01

    A porous phenolsulphonic acid-formaldehyde resin (PAFR) was developed. The heterogeneous catalyst PAFR was applied to the esterification of carboxylic acids and alcohols, affording the carboxylic acid esters in a yield of up to 95% where water was not removed from the reaction mixture. Surprisingly, the esterification in water as a solvent proceeded to afford the desired esters in high yield. PAFR provided the corresponding esters in higher yield than other homogeneous and heterogeneous catalysts. The transesterification of alcohols and esters was also investigated by using PAFR, giving the corresponding esters. PAFR was applied to the batch-wise and continuous-flow production of biodiesel fuel FAME. The PAFR-packed flow reactor that was developed for the synthesis of carboxylic acids and FAME worked for four days without loss of its catalytic activity. PMID:27189631

  13. High enantioselective Novozym 435-catalyzed esterification of (R,S)-flurbiprofen monitored with a chiral stationary phase.

    PubMed

    Siódmiak, Tomasz; Mangelings, Debby; Vander Heyden, Yvan; Ziegler-Borowska, Marta; Marszałł, Michał Piotr

    2015-03-01

    Lipases form Candida rugosa and Candida antarctica were tested for their application in the enzymatic kinetic resolution of (R,S)-flurbiprofen by enantioselective esterification. Successful chromatographic separation with well-resolved peaks of (R)- and (S)-flurbiprofen and their esters was achieved in one run on chiral stationary phases by high-performance liquid chromatography (HPLC). In this study screening of enzymes was performed, and Novozym 435 was selected as an optimal catalyst for obtaining products with high enantiopurity. Additionally, the influence of organic solvents (dichloromethane, dichloroethane, dichloropropane, and methyl tert-butyl ether), primary alcohols (methanol, ethanol, n-propanol, and n-butanol), reaction time, and temperature on the enantiomeric ratio and conversion was tested. The high values of enantiomeric ratio (E in the range of 51.3-90.5) of the esterification of (R,S)-flurbiprofen were obtained for all tested alcohols using Novozym 435, which have a great significance in the field of biotechnological synthesis of drugs. The optimal temperature range for the performed reactions was from 37 to 45 °C. As a result of the optimization, (R)-flurbiprofen methyl ester was obtained with a high optical purity, eep = 96.3 %, after 96 h of incubation. The enantiomeric ratio of the reaction was E = 90.5 and conversion was C = 35.7 %.

  14. Kinetics of Non-Catalytic Esterification of Free Fatty Acids Present in Jatropha Oil.

    PubMed

    Prasanna Rani, Karna Narayana; Ramana Neeharika, Tulasi Sri Venkata; Kumar, Thella Prathap; Satyavathi, Bankupalli; Sailu, Chintha

    2016-05-01

    Non-catalytic esterfication of free fatty acids (FFA) present in vegetable oils is an alternative pretreatment process for the biodiesel production. Biodiesel, consists of long-chain fatty acid methyl esters (FAME) and is obtained from renewable sources such as vegetable oils or animal fat. This study presents kinetics of thermal esterification of free fatty acids present in jatropha oil with methanol. The effect of process parameters like reaction time (1-5 h), temperature (170-190°C) and oil to methanol ratio (1:3-1:5) at constant pressure was investigated. The optimal conditions were found to be oil to methanol ratio of 1:4, 190°C, at 27.1 bar and 5 h which gave a maximum conversion of 95.1%. A second order kinetic model for both forward and backward reactions was proposed to study the reaction system. A good agreement was observed between the experimental data and the model values. The activation energy for forward reaction and the heat of reaction were found to be 36.364 Kcal/mol and 1.74 Kcal/mol respectively.

  15. Glycerin esterification of scum derived free fatty acids for biodiesel production.

    PubMed

    Anderson, Erik; Addy, Min; Xie, Qinglong; Ma, Huan; Liu, Yuhuan; Cheng, Yanling; Onuma, Nonso; Chen, Paul; Ruan, Roger

    2016-01-01

    Scum is an oily waste stream of the wastewater treatment process that can be used to produce biodiesel. Combining acid hydrolysis and solvent extraction, a free fatty acid and acyl-glycerol rich product was produced. Free fatty acids (FFAs) present were converted to acyl-glycols via a high temperature (238°C) glycerin esterification process known as glycerolysis. The inorganic catalysts zinc aluminum oxide and sodium sulfate were tested during glycerolysis to compare the reaction kinetics of converting FFA to acyl-glycerols. It was concluded that the zinc-based catalyst increased the reaction rate significantly, from a "k" value of 2.57 (uncatalyzed) to 5.63, completing the reaction in 60min, half the time it took the uncatalyzed reaction (120min). Sodium sulfate's presence however slowed the reaction, resulting in a "k" value of 1.45, completing the reaction in 180min. Use of the external catalyst Zn-Al2O3 showed the greatest catalytic potential, but also assumes additional costs.

  16. Optimization of esterification of oleic acid and trimethylolpropane (TMP) and pentaerythritol (PE)

    SciTech Connect

    Mahmud, Hamizah Ammarah; Salimon, Jumat

    2014-09-03

    Vegetable oil (VO) is the most potential alternative to replace mineral oil for lubricant due to better lubricating properties and great physicochemical properties. Chemical modification has to be done to overcome low temperature performance and low oxidation instability due to the presence of β-hydrogen atoms of glycerol molecule. The optimization of esterification of oleic acid and polyhydric alcohol with sulfuric acid catalyst was carried out to find the optimum conditions with the highest yield. Reeaction variables such as; molar ratio, temperature, duration and catalyst concentration. Two types of polyhydric alcohol have been used; TMP and PE. The optimum results showed oleic acid successfully converted 91.2% ester TMP and 92.7% ester PE at duration: 5 hours (Ester TMP), 6 hours (Ester PE); temperature: 150°C (ester TMP), 180°C (Ester PE); catalyst concentration: 1.5% (w/w); and mol ratio: 3.9:1 (ester TMP), 4.9:1 (ester PE). From the data obtained, mole ratio showed most influenced factors to the increasing yields of ester conversions.. The TMP/PE ester was confirmed using gas chromatography (GC-FID), Fourier Transform Infrared Spectroscopy (FTIR) and Nuclear Magnetic Resonance (NMR)

  17. Optimization of esterification of oleic acid and trimethylolpropane (TMP) and pentaerythritol (PE)

    NASA Astrophysics Data System (ADS)

    Mahmud, Hamizah Ammarah; Salimon, Jumat

    2014-09-01

    Vegetable oil (VO) is the most potential alternative to replace mineral oil for lubricant due to better lubricating properties and great physicochemical properties. Chemical modification has to be done to overcome low temperature performance and low oxidation instability due to the presence of β-hydrogen atoms of glycerol molecule. The optimization of esterification of oleic acid and polyhydric alcohol with sulfuric acid catalyst was carried out to find the optimum conditions with the highest yield. Reeaction variables such as; molar ratio, temperature, duration and catalyst concentration. Two types of polyhydric alcohol have been used; TMP and PE. The optimum results showed oleic acid successfully converted 91.2% ester TMP and 92.7% ester PE at duration: 5 hours (Ester TMP), 6 hours (Ester PE); temperature: 150°C (ester TMP), 180°C (Ester PE); catalyst concentration: 1.5% (w/w); and mol ratio: 3.9:1 (ester TMP), 4.9:1 (ester PE). From the data obtained, mole ratio showed most influenced factors to the increasing yields of ester conversions.. The TMP/PE ester was confirmed using gas chromatography (GC-FID), Fourier Transform Infrared Spectroscopy (FTIR) and Nuclear Magnetic Resonance (NMR).

  18. Kinetics of Non-Catalytic Esterification of Free Fatty Acids Present in Jatropha Oil.

    PubMed

    Prasanna Rani, Karna Narayana; Ramana Neeharika, Tulasi Sri Venkata; Kumar, Thella Prathap; Satyavathi, Bankupalli; Sailu, Chintha

    2016-05-01

    Non-catalytic esterfication of free fatty acids (FFA) present in vegetable oils is an alternative pretreatment process for the biodiesel production. Biodiesel, consists of long-chain fatty acid methyl esters (FAME) and is obtained from renewable sources such as vegetable oils or animal fat. This study presents kinetics of thermal esterification of free fatty acids present in jatropha oil with methanol. The effect of process parameters like reaction time (1-5 h), temperature (170-190°C) and oil to methanol ratio (1:3-1:5) at constant pressure was investigated. The optimal conditions were found to be oil to methanol ratio of 1:4, 190°C, at 27.1 bar and 5 h which gave a maximum conversion of 95.1%. A second order kinetic model for both forward and backward reactions was proposed to study the reaction system. A good agreement was observed between the experimental data and the model values. The activation energy for forward reaction and the heat of reaction were found to be 36.364 Kcal/mol and 1.74 Kcal/mol respectively. PMID:27086997

  19. In-Water and Neat Batch and Continuous-Flow Direct Esterification and Transesterification by a Porous Polymeric Acid Catalyst

    NASA Astrophysics Data System (ADS)

    Baek, Heeyoel; Minakawa, Maki; Yamada, Yoichi M. A.; Han, Jin Wook; Uozumi, Yasuhiro

    2016-05-01

    A porous phenolsulphonic acid—formaldehyde resin (PAFR) was developed. The heterogeneous catalyst PAFR was applied to the esterification of carboxylic acids and alcohols, affording the carboxylic acid esters in a yield of up to 95% where water was not removed from the reaction mixture. Surprisingly, the esterification in water as a solvent proceeded to afford the desired esters in high yield. PAFR provided the corresponding esters in higher yield than other homogeneous and heterogeneous catalysts. The transesterification of alcohols and esters was also investigated by using PAFR, giving the corresponding esters. PAFR was applied to the batch-wise and continuous-flow production of biodiesel fuel FAME. The PAFR-packed flow reactor that was developed for the synthesis of carboxylic acids and FAME worked for four days without loss of its catalytic activity.

  20. In-Water and Neat Batch and Continuous-Flow Direct Esterification and Transesterification by a Porous Polymeric Acid Catalyst

    PubMed Central

    Baek, Heeyoel; Minakawa, Maki; Yamada, Yoichi M. A.; Han, Jin Wook; Uozumi, Yasuhiro

    2016-01-01

    A porous phenolsulphonic acid—formaldehyde resin (PAFR) was developed. The heterogeneous catalyst PAFR was applied to the esterification of carboxylic acids and alcohols, affording the carboxylic acid esters in a yield of up to 95% where water was not removed from the reaction mixture. Surprisingly, the esterification in water as a solvent proceeded to afford the desired esters in high yield. PAFR provided the corresponding esters in higher yield than other homogeneous and heterogeneous catalysts. The transesterification of alcohols and esters was also investigated by using PAFR, giving the corresponding esters. PAFR was applied to the batch-wise and continuous-flow production of biodiesel fuel FAME. The PAFR-packed flow reactor that was developed for the synthesis of carboxylic acids and FAME worked for four days without loss of its catalytic activity. PMID:27189631

  1. Esterification of oleic acid in a three-phase, fixed-bed reactor packed with a cation exchange resin catalyst.

    PubMed

    Son, Sung Mo; Kimura, Hiroko; Kusakabe, Katsuki

    2011-01-01

    Esterification of oleic acid was performed in a three-phase fixed-bed reactor with a cation exchange resin catalyst (Amberlyst-15) at high temperature, which was varied from 80 to 120 °C. The fatty acid methyl ester (FAME) yields in the fixed-bed reactor were increased with increases in the reaction temperature, methanol flow rate and bed height. Moreover, the FAME yields were higher than those obtained using a batch reactor due to an equilibrium shift toward the product that resulted from continuous evaporation of the produced water. In addition, there was no catalyst deactivation during the esterification of oleic acid. However, addition of sunflower oil to the oleic acid reduced the FAME yield obtained from simultaneous esterification and transesterification. The FAME yield was 97.5% at a reaction temperature of 100 °C in the fixed-bed with a height of 5 cm when the methanol and oleic acid feed rates were 8.6 and 9.0 mL/h, respectively.

  2. The effect of BAY o 2752 on bile acid absorption and cholesterol esterification

    SciTech Connect

    Harnett, K.M.

    1988-01-01

    BAY o 2752 (N,N-(1,11-undecandiyl)bis(2,3-dihydro-2-methyl-1H-indole-1-carboxamide)) has been demonstrated to inhibit intestinal cholesterol absorption in rats. Studies were carried out on male Wistar rats to determine if this drug alters intestinal bile acid absorption or cholesterol esterification by acyl CoA: cholesterol acyltransferase (ACAT) or cholesterol ester hydrolase (CEH). BAY o 2752 did not affect intestinal absorption of taurocholic acid (TC) from ileal segments perfused in vivo with a tragacanth suspension in phosphate buffer containing NaCl, TC, and 24-{sup 14}C-TC as determined by the excretory rate of radioactivity in bile. BAY o 2752 also did not affect the uptake of TC into ileal everted sacs incubated in stirred, gassed Krebs-Ringer bicarbonate buffer with 1 mM TC, 24-{sup 14}C-TC and {sup 3}H-inulin. BAY o 2752 also did not bind TC; TG, in a filtrate of the above solutions remained at 92-98% of control.

  3. Biodiesel synthesis via esterification of feedstock with high content of free fatty acids.

    PubMed

    Souza, Marcella S; Aguieiras, Erika C G; da Silva, Mônica A P; Langone, Marta A P

    2009-05-01

    The objective of this work was to study the synthesis of ethyl esters via esterification of soybean oil deodorizer distillate with ethanol, using solid acid catalysts and commercial immobilized lipases, in a solvent-free system. Three commercially immobilized lipases were used, namely, Lipozyme RM-IM, Lipozyme TL-IM, and Novozym 435, all from Novozymes. We aimed for optimum reaction parameters: temperature, enzyme concentration, initial amount of ethanol, and its feeding technique to the reactor (stepwise ethanolysis). Reaction was faster with Novozym 435. The highest conversion (83.5%) was obtained after 90 min using 3 wt.% of Novozym 435 and two-stage stepwise addition of ethanol at 50 degrees C. Four catalysts were also tested: zeolite CBV-780, SAPO-34, niobia, and niobic acid. The highest conversion (30%) was obtained at 100 degrees C, with 3 wt.% of CBV-780 after 2.5 h. The effects of zeolite CBV 780 concentration were studied, resulting in a conversion of 49% using 9 wt.% of catalyst. PMID:19067243

  4. Liquid phase esterification of acetic acid over WO3 promoted β-SiC in a solvent free system.

    PubMed

    Mishra, Gopa; Behera, Gobinda C; Singh, S K; Parida, K M

    2012-12-21

    A series of tungstate promoted β-SiC catalysts was synthesized by a wetness impregnation method. The as synthesized catalysts were unambiguously characterized by XRD, Raman, FTIR, XPS, UV-Vis DRS, TEM, BET surface areas and FE-SEM, and simultaneously the total amount of the acidity of the catalysts was estimated by NH(3)-TPD. The catalytic activities of the synthesized materials were tested in the liquid phase esterification of acetic acid with n-butanol in a solvent free medium. The reaction parameters were optimized to a temperature of 120 °C, molar ratio of butanol and acetic acid of 1:2 and a reaction time of 6 h after performing a number of experiments. Under the optimum conditions, the catalytic esterification revealed a significant effect of 88% conversion with 100% selectivity to butyl acetate in 20 wt% WO(3)/β-SiC. This is the first report on the effective utilization of β-SiC as a catalyst support for liquid phase esterification of acetic acid.

  5. Fatty acid steryl, stanyl, and steroid esters by esterification and transesterification in vacuo using Candida rugosa lipase as catalyst.

    PubMed

    Weber, N; Weitkamp, P; Mukherjee, K D

    2001-01-01

    Sterols (sitosterol, cholesterol, stigmasterol, ergosterol, and 7-dehydrocholesterol) and sitostanol have been converted in high to near-quantitative yields to the corresponding long-chain acyl esters via esterification with fatty acids or transesterification with methyl esters of fatty acids or triacylglycerols using lipase from Candida rugosa as biocatalyst in vacuo (20-40 mbar) at 40 degrees C. Neither organic solvent nor water is added in these reactions. Under similar conditions, cholesterol has been converted to cholesteryl butyrate and steroids (5alpha-pregnan-3beta-ol-20-one or 5-pregnen-3beta-ol-20-one) have been converted to their propionic acid esters, both in moderate to high yields, via transesterification with tributyrin and tripropionin, respectively. Reaction parameters studied in esterification include the temperature and the molar ratio of the substrates as well as the amount and reuse properties of the C. rugosa lipase. Lipases from porcine pancreas, Rhizopus arrhizus, and Chromobacterium viscosum are quite ineffective as biocatalysts for the esterification of cholesterol with oleic acid under the above conditions.

  6. Kinetic study of esterification of sulfuric acid with alcohols in aerosol bulk phase

    NASA Astrophysics Data System (ADS)

    Li, J.; Jang, M.

    2013-09-01

    In this study, we hypothesize that the formation of organosulfates through the reactions between sulfuric acid and alcohols in the aerosol bulk phase is more efficient than that in solution chemistry. To prove this hypothesis, the kinetics of the organosulfate formation was investigated for both aliphatic alcohol with single OH group (e.g., 1-heptanol) and the multialcohols ranging from semivolatiles (e.g., hydrated-glyoxal and glycerol) to nonvolatiles (e.g., sucrose) using analytical techniques directly monitoring aerosol bulk phase. Both the forward (k1) and the backward (k-1) reaction rate constants of organosulfate formation via the particle phase esterification of 1-heptanol with sulfuric acid were estimated using a Fourier Transform Infrared (FTIR) spectrometer equipped with a flow chamber under varying humidities. Both k1 and k-1 are in orders of 10-3 L mol-1 min-1, which are three orders of magnitude higher than the reported values obtained in solution chemistry. The formation of organosulfate in the H2SO4 aerosol internally mixed with multialcohols was studied by measuring the proton concentration of the aerosol collected on the filter using a newly developed Colorimetry integrated with a Reflectance UV-Visible spectrometer (C-RUV). The formation of organosulfate significantly decreases aerosol acidity due to the transformation of H2SO4 into dialkylsulfates. The forward reaction rate constants for the dialkylsulfate formation in the multialcohol-H2SO4 aerosols were also three orders of magnitude greater than the reported values in solution chemistry. The water content (MH2O) in the multialcohol-H2SO4 particle was monitored using the FTIR spectrometer. A large reduction of MH2O accords with the high yield of organosulfate in aerosol. Based on this study, we conclude that organosulfate formation in atmospheric aerosol, where both alcohols and sulfuric acid are found together, is significant.

  7. Acid-catalyzed hot-water extraction of lipids from Chlorella vulgaris.

    PubMed

    Park, Ji-Yeon; Oh, You-Kwan; Lee, Jin-Suk; Lee, Kyubock; Jeong, Min-Ji; Choi, Sun-A

    2014-02-01

    Acid-catalyzed hot-water treatment for efficient extraction of lipids from a wet microalga, Chlorella vulgaris, was investigated. For an initial fatty acids content of 381.6mg/g cell, the extracted-lipid yield with no heating and no catalyst was 83.2mg/g cell. Under a 1% H2SO4 concentration heated at 120°C for 60min, however, the lipid-extraction yield was 337.4mg/g cell. The fatty acids content, meanwhile, was 935mg fatty acid/g lipid. According to the severity index formula, 337.5mg/g cell of yield under the 1% H2SO4 concentration heated at 150°C for 8min, and 334.2mg/g cell of yield under the 0.5% H2SO4 concentration heated at 150°C for 16min, were obtained. The lipids extracted by acid-catalyzed hot-water treatment were converted to biodiesel. The biodiesel's fatty acid methyl ester (FAME) content after esterification of the microalgal lipids was increased to 79.2% by the addition of excess methanol and sulfuric acid.

  8. Acid-Catalyzed Isomerization of Carvone to Carvacrol

    ERIC Educational Resources Information Center

    Kjonaas, Richard A.; Mattingly, Shawn P.

    2005-01-01

    The acid-catalyzed isomerization of carvone to carvacrol, first reported by Ritter and Ginsburg, is especially well suited with a permanent-magnet FT instrument. The acid-catalyzed isomerization of carvone to carvacrol produced a 61% yield after a three hour reflux with 30% aqueous sulfuric acid.

  9. Monodispersed Hollow SO3H-Functionalized Carbon/Silica as Efficient Solid Acid Catalyst for Esterification of Oleic Acid.

    PubMed

    Wang, Yang; Wang, Ding; Tan, Minghui; Jiang, Bo; Zheng, Jingtang; Tsubaki, Noritatsu; Wu, Mingbo

    2015-12-01

    SO3H-functionalized monodispersed hollow carbon/silica spheres (HS/C-SO3H) with primary mesopores were prepared with polystyrene as a template and p-toluenesulfonic acid (TsOH) as a carbon precursor and -SO3H source simultaneously. The physical and chemical properties of HS/C-SO3H were characterized by N2 adsorption, TEM, SEM, XPS, XRD, Raman spectrum, NH3-TPD, element analysis and acid-base titration techniques. As a solid acid catalyst, HS/C-SO3H shows excellent performance in the esterification of oleic acid with methanol, which is a crucial reaction in biodiesel production. The well-defined hollow architecture and enhanced active sites accessibility of HS/C-SO3H guarantee the highest catalytic performance compared with the catalysts prepared by activation of TsOH deposited on the ordered mesoporous silicas SBA-15 and MCM-41. At the optimized conditions, high conversion (96.9%) was achieved and no distinct activity drop was observed after 5 recycles. This synthesis strategy will provide a highly effective solid acid catalyst for green chemical processes.

  10. Monodispersed Hollow SO3H-Functionalized Carbon/Silica as Efficient Solid Acid Catalyst for Esterification of Oleic Acid.

    PubMed

    Wang, Yang; Wang, Ding; Tan, Minghui; Jiang, Bo; Zheng, Jingtang; Tsubaki, Noritatsu; Wu, Mingbo

    2015-12-01

    SO3H-functionalized monodispersed hollow carbon/silica spheres (HS/C-SO3H) with primary mesopores were prepared with polystyrene as a template and p-toluenesulfonic acid (TsOH) as a carbon precursor and -SO3H source simultaneously. The physical and chemical properties of HS/C-SO3H were characterized by N2 adsorption, TEM, SEM, XPS, XRD, Raman spectrum, NH3-TPD, element analysis and acid-base titration techniques. As a solid acid catalyst, HS/C-SO3H shows excellent performance in the esterification of oleic acid with methanol, which is a crucial reaction in biodiesel production. The well-defined hollow architecture and enhanced active sites accessibility of HS/C-SO3H guarantee the highest catalytic performance compared with the catalysts prepared by activation of TsOH deposited on the ordered mesoporous silicas SBA-15 and MCM-41. At the optimized conditions, high conversion (96.9%) was achieved and no distinct activity drop was observed after 5 recycles. This synthesis strategy will provide a highly effective solid acid catalyst for green chemical processes. PMID:26588826

  11. Radical scavenging activity of lipophilized products from lipase-catalyzed transesterification of triolein with cinnamic and ferulic acids.

    PubMed

    Choo, Wee-Sim; Birch, Edward John

    2009-02-01

    Lipase-catalyzed transesterification of triolein with cinnamic and ferulic acids using an immobilized lipase from Candida antarctica (E.C. 3.1.1.3) was conducted to evaluate the antioxidant activity of the lipophilized products as model systems for enhanced protection of unsaturated oil. The lipophilized products were identified using ESI-MS. Free radical scavenging activity was determined using the DPPH radical method. The polarity of the solvents proved important in determining the radical scavenging activity of the substrates. Ferulic acid showed much higher radical scavenging activity than cinnamic acid, which has limited activity. The esterification of cinnamic acid and ferulic acid with triolein resulted in significant increase and decrease in the radical scavenging activity, respectively. These opposite effects were due to the effect of addition of electron-donating alkyl groups on the predominant mechanism of reaction (hydrogen atom transfer or electron transfer) of a species with DPPH. The effect of esterification of cinnamic acid was confirmed using ethyl cinnamate which greatly enhances the radical scavenging activity. Although, compared to the lipophilized cinnamic acid product, the activity was lower. The radical scavenging activity of the main component isolated from lipophilized cinnamic acid product using solid phase extraction, monocinnamoyl dioleoyl glycerol, was as good as the unseparated mixture of lipophilized product. Based on the ratio of a substrate to DPPH concentration, lipophilized ferulic acid was a much more efficient radical scavenger than lipophilized cinnamic acid.

  12. Kinetics of the esterification of active pharmaceutical ingredients containing carboxylic acid functionality in polyethylene glycol: formulation implications.

    PubMed

    Schou-Pedersen, Anne Marie V; Hansen, Steen Honoré; Moesgaard, Birthe; Østergaard, Jesper

    2014-08-01

    Polyethylene glycols (PEGs) are attractive as excipients in the manufacture of drug products because they are water soluble and poorly immunogenic. They are used in various pharmaceutical preparations. However, because of their terminal hydroxyl groups, PEGs can participate in esterification reactions. In this study, kinetics of two active pharmaceutical ingredients, cetirizine and indomethacin possessing carboxylic acid functionality, has been studied in PEG 400 and PEG 1000 at 50 °C, 60 °C, 70 °C, and 80 °C. HPLC-UV was applied for the determination of concentrations in the kinetic studies, whereas HPLC-MS was used to identify reaction products. The esterification reactions were observed to be reversible. A second-order reversible kinetic model was applied and rate constants were determined. The rate constants demonstrated that cetirizine was esterified about 240 times faster than indomethacin at 80 °C. The shelf-life for cetirizine in a PEG 400 formulation at 25 °C expressed as t(95%) was predicted to be only 30 h. Further, rate constants for esterification of cetirizine in PEG 1000 in relation to PEG 400 decreased by a factor of 10, probably related to increased viscosity. However, it is important to be aware of this drug-excipient interaction, as it can reduce the shelf-life of a low-average molecular weight PEG formulation considerably.

  13. Synthesis and evaluation of odour-active methionyl esters of fatty acids via esterification and transesterification of butter oil.

    PubMed

    Li, Cheng; Sun, Jingcan; Fu, Caili; Yu, Bin; Liu, Shao Quan; Li, Tianhu; Huang, Dejian

    2014-02-15

    Methionol-derived fatty acid esters were synthesised by both chemical and lipase catalysed esterification between fatty acids and methionol. Beneficial effects of both methods were compared qualitatively and quantitatively by GC-MS/GC-FID results. And the high acid and heat stability of our designed methionyl esters meet the requirement of the food industry. Most importantly, the sensory test showed that fatty acid carbon-chain length had an important effect on the flavour attributes of methionyl esters. Moreover, through Lipozyme TL IM-mediated transesterification, valuable methionol-derived esters were synthesised from the readily available natural material butter oil as the fatty acid source. The conversion of methionol and yield of each methionyl ester were also elucidated by GC-MS-FID.

  14. Influences of fatty acid moiety and esterification of polyglycerol fatty acid esters on the crystallization of palm mid fraction in oil-in-water emulsion.

    PubMed

    Sakamoto, Mitsuhiro; Ohba, Azusa; Kuriyama, Juhei; Maruo, Kouichi; Ueno, Satoru; Sato, Kiyotaka

    2004-08-15

    We examined the crystallization of palm mid fraction (PMF) in oil-in-water (O/W) emulsion, after adding polyglycerol fatty acid esters (PGFEs). We employed ultrasonic velocity measurements and DSC techniques, with special emphases on the influences of fatty acid moiety and esterification of PGFE. Twelve types of PGFEs were examined as additives. PGFEs have a large hydrophilic moiety composed of 10 glycerol molecules to which palmitic, stearic and behenic acids were esterified as the fatty acid moiety with different degrees of esterification. Crystallization temperature (T(c)) of PMF remarkably increased with increasing concentrations of the PGFEs as the chain length of the fatty acid moiety increased, and the PGFE became more hydrophobic in accordance with increasing degree of esterification. We observed that the heterogeneous nucleation of PMF in the O/W emulsion was activated at the oil-water interface, where the template effect of very hydrophobic long saturated fatty acid chains of the PGFE might play the main role of heterogeneous nucleation.

  15. Tailoring the Synergistic Bronsted-Lewis acidic effects in Heteropolyacid catalysts: Applied in Esterification and Transesterification Reactions

    NASA Astrophysics Data System (ADS)

    Tao, Meilin; Xue, Lifang; Sun, Zhong; Wang, Shengtian; Wang, Xiaohong; Shi, Junyou

    2015-09-01

    In order to investigate the influences of Lewis metals on acidic properties and catalytic activities, a series of Keggin heteropolyacid (HPA) catalysts, HnPW11MO39 (M = TiIV, CuII, AlIII, SnIV, FeIII, CrIII, ZrIV and ZnII; for Ti and Zr, the number of oxygen is 40), were prepared and applied in the esterification and transesterification reactions. Only those cations with moderate Lewis acidity had a higher impact. Ti Substituted HPA, H5PW11TiO40, posse lower acid content compared with TixH3-4xPW12O40 (Ti partial exchanged protons in saturated H3PW12O40), which demonstrated that the Lewis metal as an addenda atom (H5PW11TiO40) was less efficient than those as counter cations (TixH3-4xPW12O40). On the other hand, the highest conversion reached 92.2% in transesterification and 97.4% in esterification. Meanwhile, a good result was achieved by H5PW11TiO40 in which the total selectivity of DAG and TGA was 96.7%. In addition, calcination treatment to H5PW11TiO40 make it insoluble in water which resulted in a heterogeneous catalyst feasible for reuse.

  16. Tailoring the Synergistic Bronsted-Lewis acidic effects in Heteropolyacid catalysts: Applied in Esterification and Transesterification Reactions.

    PubMed

    Tao, Meilin; Xue, Lifang; Sun, Zhong; Wang, Shengtian; Wang, Xiaohong; Shi, Junyou

    2015-09-16

    In order to investigate the influences of Lewis metals on acidic properties and catalytic activities, a series of Keggin heteropolyacid (HPA) catalysts, HnPW11MO39 (M = Ti(IV), Cu(II), Al(III), Sn(IV), Fe(III), Cr(III), Zr(IV) and Zn(II); for Ti and Zr, the number of oxygen is 40), were prepared and applied in the esterification and transesterification reactions. Only those cations with moderate Lewis acidity had a higher impact. Ti Substituted HPA, H5PW11TiO40, posse lower acid content compared with Ti(x)H(3-4x)PW12O40 (Ti partial exchanged protons in saturated H3PW12O40), which demonstrated that the Lewis metal as an addenda atom (H5PW11TiO40) was less efficient than those as counter cations (Ti(x)H(3-4x)PW12O40). On the other hand, the highest conversion reached 92.2% in transesterification and 97.4% in esterification. Meanwhile, a good result was achieved by H5PW11TiO40 in which the total selectivity of DAG and TGA was 96.7%. In addition, calcination treatment to H5PW11TiO40 make it insoluble in water which resulted in a heterogeneous catalyst feasible for reuse.

  17. Continuous esterification of free fatty acids in crude biodiesel by an integrated process of supercritical methanol and sodium methoxide catalyst.

    PubMed

    Zeng, Dan; Li, Ruosong; Feng, Mingjun; Fang, Tao

    2014-10-01

    An integrated process of supercritical methanol (SCM) and sodium methoxide catalyst was developed to produce fatty acid methyl esters (FAMEs) via continuous esterification from crude biodiesel. The crude biodiesel with high free fatty acid (FFA) content must be refined to reduce the acid value (AV) for meeting the quality standards. The process parameters were studied by Box-Behnken design (BBD) of response surface methodology (RSM). The experimental results revealed that the AV of crude biodiesel decreased from 18.66 to 0.55 mg KOH g(-1) at the reaction conditions of 350 °C, 0.5 % amount of sodium methoxide catalyst, and 10 MPa. Temperature shows the most significant effect on the esterification, followed by pressure and amount of sodium methoxide catalyst. This integrated process proved to be a potential route to refine the crude biodiesel because of its continuity, high efficiency, and less energy consumption with relatively moderate reaction conditions compared with conventional methods.

  18. Tailoring the Synergistic Bronsted-Lewis acidic effects in Heteropolyacid catalysts: Applied in Esterification and Transesterification Reactions

    PubMed Central

    Tao, Meilin; Xue, Lifang; Sun, Zhong; Wang, Shengtian; Wang, Xiaohong; Shi, Junyou

    2015-01-01

    In order to investigate the influences of Lewis metals on acidic properties and catalytic activities, a series of Keggin heteropolyacid (HPA) catalysts, HnPW11MO39 (M = TiIV, CuII, AlIII, SnIV, FeIII, CrIII, ZrIV and ZnII; for Ti and Zr, the number of oxygen is 40), were prepared and applied in the esterification and transesterification reactions. Only those cations with moderate Lewis acidity had a higher impact. Ti Substituted HPA, H5PW11TiO40, posse lower acid content compared with TixH3−4xPW12O40 (Ti partial exchanged protons in saturated H3PW12O40), which demonstrated that the Lewis metal as an addenda atom (H5PW11TiO40) was less efficient than those as counter cations (TixH3−4xPW12O40). On the other hand, the highest conversion reached 92.2% in transesterification and 97.4% in esterification. Meanwhile, a good result was achieved by H5PW11TiO40 in which the total selectivity of DAG and TGA was 96.7%. In addition, calcination treatment to H5PW11TiO40 make it insoluble in water which resulted in a heterogeneous catalyst feasible for reuse. PMID:26374393

  19. Synthesis of 2-monoacylglycerols and structured triacylglycerols rich in polyunsaturated fatty acids by enzyme catalyzed reactions.

    PubMed

    Rodríguez, Alicia; Esteban, Luis; Martín, Lorena; Jiménez, María José; Hita, Estrella; Castillo, Beatriz; González, Pedro A; Robles, Alfonso

    2012-08-10

    This paper studies the synthesis of structured triacylglycerols (STAGs) by a four-step process: (i) obtaining 2-monoacylglycerols (2-MAGs) by alcoholysis of cod liver oil with several alcohols, catalyzed by lipases Novozym 435, from Candida antartica and DF, from Rhizopus oryzae, (ii) purification of 2-MAGs, (iii) formation of STAGs by esterification of 2-MAGs with caprylic acid catalyzed by lipase DF, from R. oryzae, and (iv) purification of these STAGs. For the alcoholysis of cod liver oil, absolute ethanol, ethanol 96% (v/v) and 1-butanol were compared; the conditions with ethanol 96% were then optimized and 2-MAG yields of around 54-57% were attained using Novozym 435. In these 2-MAGs, DHA accounted for 24-31% of total fatty acids. In the operational conditions this lipase maintained a stable level of activity over at least 11 uses. These results were compared with those obtained with lipase DF, which deactivated after only three uses. The alcoholysis of cod liver oil and ethanol 96% catalyzed by Novozym 435 was scaled up by multiplying the reactant amounts 100-fold and maintaining the intensity of treatment constant (IOT=3g lipase h/g oil). In these conditions, the 2-MAG yield attained was about 67%; these 2-MAGs contained 36.6% DHA. The synthesized 2-MAGs were separated and purified from the alcoholysis reaction products by solvent extraction using solvents of low toxicity (ethanol and hexane); 2-MAG recovery yield and purity of the target product were approximately 96.4% and 83.9%, respectively. These 2-MAGs were transformed to STAGs using the optimal conditions obtained in a previous work. After synthesis and purification, 93% pure STAGs were obtained, containing 38% DHA at sn-2 position and 60% caprylic acid (CA) at sn-1,3 positions (of total fatty acids at these positions), i.e. the major TAG is the STAG with the structure CA-DHA-CA. PMID:22759534

  20. Synthesis of 2-monoacylglycerols and structured triacylglycerols rich in polyunsaturated fatty acids by enzyme catalyzed reactions.

    PubMed

    Rodríguez, Alicia; Esteban, Luis; Martín, Lorena; Jiménez, María José; Hita, Estrella; Castillo, Beatriz; González, Pedro A; Robles, Alfonso

    2012-08-10

    This paper studies the synthesis of structured triacylglycerols (STAGs) by a four-step process: (i) obtaining 2-monoacylglycerols (2-MAGs) by alcoholysis of cod liver oil with several alcohols, catalyzed by lipases Novozym 435, from Candida antartica and DF, from Rhizopus oryzae, (ii) purification of 2-MAGs, (iii) formation of STAGs by esterification of 2-MAGs with caprylic acid catalyzed by lipase DF, from R. oryzae, and (iv) purification of these STAGs. For the alcoholysis of cod liver oil, absolute ethanol, ethanol 96% (v/v) and 1-butanol were compared; the conditions with ethanol 96% were then optimized and 2-MAG yields of around 54-57% were attained using Novozym 435. In these 2-MAGs, DHA accounted for 24-31% of total fatty acids. In the operational conditions this lipase maintained a stable level of activity over at least 11 uses. These results were compared with those obtained with lipase DF, which deactivated after only three uses. The alcoholysis of cod liver oil and ethanol 96% catalyzed by Novozym 435 was scaled up by multiplying the reactant amounts 100-fold and maintaining the intensity of treatment constant (IOT=3g lipase h/g oil). In these conditions, the 2-MAG yield attained was about 67%; these 2-MAGs contained 36.6% DHA. The synthesized 2-MAGs were separated and purified from the alcoholysis reaction products by solvent extraction using solvents of low toxicity (ethanol and hexane); 2-MAG recovery yield and purity of the target product were approximately 96.4% and 83.9%, respectively. These 2-MAGs were transformed to STAGs using the optimal conditions obtained in a previous work. After synthesis and purification, 93% pure STAGs were obtained, containing 38% DHA at sn-2 position and 60% caprylic acid (CA) at sn-1,3 positions (of total fatty acids at these positions), i.e. the major TAG is the STAG with the structure CA-DHA-CA.

  1. Pd-catalyzed arylation of chlorotrifluoroethylene using arylboronic acids.

    PubMed

    Yamamoto, Tetsuya; Yamakawa, Tetsu

    2012-07-01

    The palladium-catalyzed cross-coupling of chlorotrifluoroethylene and arylboronic acids proceeds in the presence of a base and H(2)O to provide α,β,β-trifluorostyrene derivatives in satisfactory yields. PMID:22691065

  2. Copper-catalyzed trifluoromethylthiolation of primary and secondary alkylboronic acids.

    PubMed

    Shao, Xinxin; Liu, Tianfei; Lu, Long; Shen, Qilong

    2014-09-19

    A Cu-catalyzed trifluoromethylthiolation of primary and secondary alkylboronic acids with an electrophilic trifluoromethylthiolating reagent is described. Tolerance for a variety of functional groups was observed. PMID:25198142

  3. Influence of two different alcohols in the esterification of fatty acids over layered zinc stearate/palmitate.

    PubMed

    de Paiva, Eduardo José Mendes; Corazza, Marcos Lúcio; Sierakowski, Maria Rita; Wärnå, Johan; Murzin, Dmitry Yu; Wypych, Fernando; Salmi, Tapio

    2015-10-01

    In this work, esterification of fatty acids (oleic, linoleic and stearic acid) with a commercial zinc carboxylate (a layered compound formed by simultaneous intercalation of stearate and palmitate anions) was performed. Kinetic modeling using a quasi-homogeneous approach successfully fitted experimental data at different molar ratio of fatty acids/alcohols (1-butanol and 1-hexanol) and temperature. An apparent first-order reaction related to all reactants was found and activation energy of 66 kJ/mol was reported. The catalyst showed to be unique, as it can be easily recovered like a heterogeneous catalysts behaving like ionic liquids. In addition, this catalyst demonstrated a peculiar behavior, because higher reactivity was observed with the increase in the alcohols chain length compared to the authors' previous work using ethanol.

  4. Esterification of essential and non-essential fatty acids into distinct lipid classes in ruminant and non-ruminant tissues.

    PubMed

    Caldari-Torres, Cristina; McGilliard, Michael L; Corl, Benjamin A

    2016-10-01

    Extensive microbial biohydrogenation of polyunsaturated fatty acids (PUFA) in the rumen reduces the essential fatty acids (EFA) available for absorption in ruminant animals, but there is no published documentation of ruminants developing EFA deficiency. In ruminants, most circulating PUFA are found in the phospholipid (PL) and cholesteryl ester lipid classes that have slow turn-over compared to other lipid classes. The objective of this experiment was to measure fatty acid esterification patterns of the non-EFA palmitic (16:0) and oleic acid (18:1), and the EFA linoleic (18:2) and linolenic acid (18:3) in small intestine, liver, and muscle tissue of cows and pigs to identify tissues participating in sequestration of these FA in less metabolically active lipid classes in ruminants. Bovine and porcine small intestine, liver, and muscle explants were prepared and incubated in media containing radiolabeled 16:0, 18:1, 18:2, or 18:3 to measure esterification of fatty acids into PL and TG. Neither bovine nor porcine small intestine explants preferentially incorporated non-EFA compared to EFA into PL vs TG. Bovine liver explants esterified a larger proportion of EFA than non-EFA into PL compared to TG, while incorporation was similar among the FA tested in porcine liver explants. Bovine muscle explants showed preferential incorporation of EFA into PL rather than TG. Results show that bovine and porcine liver and muscle esterify EFA and non-EFA differently and that the conservation of EFA in ruminants is a result of preferential incorporation of EFA into PL mediated by bovine liver and muscle, but not the small intestine. PMID:27134010

  5. Hierarchically structured meso-macroporous aluminosilicates with high tetrahedral aluminium content in acid catalysed esterification of fatty acids.

    PubMed

    Lemaire, Arnaud; Wang, Quan-Yi; Wei, Yingxu; Liu, Zhongmin; Su, Bao-Lian

    2011-11-15

    A simple synthesis pathway has been developed for the design of hierarchically structured spongy or spherical voids assembled meso-macroporous aluminosilicates with high tetrahedral aluminium content on the basis of the aqueous polymerisation of new stabilized alkoxy-bridged single molecular precursors. The intimate mixing of an aluminosilicate ester (sec-BuO)(2)-Al-O-Si(OEt)(3) and a silica co-reactant (tetramethoxysilane, TMOS) with variable ratios and the use of alkaline solutions (pH 13.0 and 13.5) improve significantly the heterocondensation rates between the highly reactive aluminium alkoxide part of the single precursor and added silica co-reactant, leading to aluminosilicate materials with high intra-framework aluminium content and low Si/Al ratios. The spherically-shaped meso-macroporosity was spontaneously generated by the release of high amount of liquid by-products (water/alcohol molecules) produced during the rapid hydrolysis and condensation processes of this double alkoxide and the TMOS co-reactant. It has been observed that both pH value and Al-Si/TMOS molar ratio can strongly affect the macroporous structure formation. Increasing pH value, even slightly from 13 to 13.5, can significantly favour the incorporation of Al atoms in tetrahedral position of the framework. After the total ionic exchange of Na(+) compensating cations, catalytic tests of obtained materials were realised in the esterification reaction of high free fatty acid (FFA) oils, showing their higher catalytic activity compared to commercial Bentonite clay, and their potential applications as catalyst supports in acid catalysed reactions.

  6. Continuous process of preparation of n-butyl(meth)acrylate by esterification of (meth)acrylic acid by butanol on thermostable sulfo-cation exchanger

    SciTech Connect

    Zheleznaya, L.L.; Karakhanov, R.A.; Lunin, A.F.; Magadov, R.S.; Meshcheryakov, S.V.; Mkrtychan, V.R.; Fomin, V.A.

    1987-11-10

    The authors propose an effective thermostable sulfo-cation exchanger based on polymers with a system of conjugated bonds, sulfopolyphenylene ketone (SPP) differing from the known cation exchangers by the high thermostability (up to 250/sup 0/C), and also having the effect of the stabilization of the double bond in unsaturated monomers. The combination of inhibiting and cation exchange properties makes it also possible to use these sulfo-cation exchangers in the processes of esterification of (meth)acrylic acids by alcohols without addition of special inhibitors. The SPP catalyst was tested in esterification processes of acrylic an methacrylic acid by butanol at a pilot plant.

  7. A comparative study of solid carbon acid catalysts for the esterification of free fatty acids for biodiesel production. Evidence for the leaching of colloidal carbon.

    PubMed

    Deshmane, Chinmay A; Wright, Marcus W; Lachgar, Abdessadek; Rohlfing, Matthew; Liu, Zhening; Le, James; Hanson, Brian E

    2013-11-01

    The preparation of a variety of sulfonated carbons and their use in the esterification of oleic acid is reported. All sulfonated materials show some loss in activity associated with the leaching of active sites. Exhaustive leaching shows that a finite amount of activity is lost from the carbons in the form of colloids. Fully leached catalysts show no loss in activity upon recycling. The best catalysts; 1, 3, and 6; show initial TOFs of 0.07 s(-1), 0.05 s(-1), and 0.14 s(-1), respectively. These compare favorably with literature values. Significantly, the leachate solutions obtained from catalysts 1, 3, and 6, also show excellent esterification activity. The results of TEM and catalyst poisoning experiments on the leachate solutions associate the catalytic activity of these solutions with carbon colloids. This mechanism for leaching active sites from sulfonated carbons is previously unrecognized.

  8. Pharmacokinetics and tissue distribution of docetaxel liposome mediated by a novel galactosylated cholesterol derivatives synthesized by lipase-catalyzed esterification in non-aqueous phase.

    PubMed

    Luo, Li-Hua; Zheng, Pin-Jing; Nie, Hua; Chen, Yu-Chao; Tong, Dan; Chen, Jin; Cheng, Yi

    2016-05-01

    The purpose of this study is to synthesize a novel galactosylated cholesterol derivative, cholesterol-diethenyl decanedioate-lactitol (CHS-DD-LA) through lipase-catalyzed esterification in non-aqueous and to evaluate the preparation, pharmacokinetics and biodistribution of docetaxel (DOC) liposomes modified with CHS-DD-LA (G-DOC-L), which may actively gather at the liver compared with the conventional DOC liposomes (DOC-L) and commercial dosage form of DOC injection (DOC-i). A rapid and simple liquid chromatography-tandem mass spectrometry (LC-MS/MS) assay was developed for the determination of the DOC concentration in plasma and tissues with Taxol as the internal standard (IS). To measure the liver-targeting effect of the G-DOC-L, relative uptake rate (Re), peak concentration ratio (Ce), targeting efficiency (Te) and relative targeting efficiency (RTe) were reduced as the evaluation parameters. The results showed that the entrapment efficiency, particle size and Zeta potential of G-DOC-L was 76.8 ± 3.5%, 95.6 nm and 27.19 mV, respectively. After i.v. administration at the dose of 2.5 mg/kg in rats, a decrease in the AUC, MRT and an increase in CL (p < 0.05) were observed in the G-DOC-L group compared with DOC-L. All these results suggested that galactose-anchored liposomes could rapidly be removed from the circulation in vivo. The tissue distribution of G-DOC-L was widely different from that of DOC-L. The Re of G-DOC-L, DOC-L on liver was 4.011, 0.102; Ce was 3.391, 0.111; Te was 55.01, 3.08, respectively, demonstrating that G-DOC-L had an excellent effect on liver-targeting, which may help to improve the therapeutic effect of hepatic diseases.

  9. Methyl Acetate Synthesis by Esterification on the Modified Ferrierite: Correlation of Acid Sites Measured by Pyridine IR and NH3-TPD for Steady-State Activity.

    PubMed

    Park, Jae Hyun; Pang, Changhyun; Chung, Chan-Hwa; Bae, Jong Wook

    2016-05-01

    The amounts of Brønsted acid sites on K, P, and Zr-modified microporous Ferrierite zeolite were investigated through pyridine FT-IR and NH3-TPD analyses. P-modified Ferrierite showed a superior catalytic activity for methyl acetate synthesis by esterification of methanol and acetic acid. The catalytic activity at steady-state with the acidic properties of as-prepared catalysts was well correlated with the results of pyridine FT-IR (intensity ratio of Brønsted acid sites to total acid sites) compared with that of NH3-TPD. The results can suggest the proper and simple method to estimate the esterification activity at steady-state using the measured acid sites on the as-prepared zeolites. PMID:27483801

  10. Monolayer structures of niobic acids supported on SiO[sub 2] and their catalytic activities for esterification of acetic acid with ethanol

    SciTech Connect

    Shirai, Masayuki; Asakura, Kiyotaka; Iwasawa, Yasuhiro )

    1991-11-28

    New submonolayer niobic acid catalysts were prepared by the reaction of Nb(OC[sub 2]H[sub 5])[sub 5] with surface OH groups of SiO[sub 2], followed by H[sub 2]O treatment. The surface structures were characterized by means of EXAFS, XRD, XRF, and FT-IR. The niobic acids on SiO[sub 2] up to 8.0 wt % Nb loadings were found to grow in a monolayer mode. These catalysts showed activities 20 times as large as that of a niobic acid bulk catalyst for the esterification of acetic acid with ethanol. The activity was referred to Lewis acid sites in the monolayer structure, which was stable even after evacuation at high temperatures such as 873 K.

  11. Rapid and simple solid-phase esterification of sialic acid residues for quantitative glycomics by mass spectrometry.

    PubMed

    Miura, Yoshiaki; Shinohara, Yasuro; Furukawa, Jun-ichi; Nagahori, Noriko; Nishimura, Shin-Ichiro

    2007-01-01

    A rapid and quantitative method for solid-phase methyl esterification of carboxy groups of various sialylated oligosaccharides has been established. The method employed a triazene derivative, 3-methyl-1-p-tolyltriazene, for facile derivatization of oligosaccharides immobilized onto general solid supports such as Affi-Gel Hz and gold colloidal nanoparticles in a multiwell plate. The workflow protocol was optimized for the solid-phase processing of captured sialylated/unsialylated oligosaccharides separated from crude sample mixtures by chemical ligation. From tryptic and/or PNGase F-digest mixtures of glycoproteins, purification by chemoselective immobilization, esterification and recovery were achieved in the same well of the filter plate within three hours when used in conjunction with "glycoblotting technology" (S.-I. Nishimura, K. Niikura, M. Kurogochi, T. Matsushita, M. Fumoto, H. Hinou, R. Kamitani, H. Nakagawa, K. Deguchi, N. Miura, K. Monde, H. Kondo, High-throughput protein glycomics: Combined use of chemoselective glycoblotting and MALDI-TOF/TOF mass spectrometry: Angew. Chem. 2005, 117, 93-98; Angew. Chem. Int. Ed. 2005, 44, 91-96). The recovered materials were directly applicable to subsequent characterization by mass spectrometric techniques such as MALDI-TOF for large-scale glycomics of both neutral and sialylated oligosaccharides. On-bead/on-gold nanoparticle derivatization of glycans containing sialic acids allowed rapid and quantitative glycoform profiling by MALDI-TOF MS with reflector and positive ion mode. In addition to its simplicity and speed, the method eliminates the use of unfavorable halogenated solvents such as chloroform and dichloromethane or volatile solvents such as diethyl ether and hexane, resulting in a practical and green chemical method for automated robotic adaptation.

  12. Nonthermal effect of microwave irradiation in nonaqueous enzymatic esterification.

    PubMed

    Wan, Hui-da; Sun, Shi-yu; Hu, Xue-yi; Xia, Yong-mei

    2012-03-01

    Microwave has nonthermal effects on enzymatic reactions, mainly caused by the polarities of the solvents and substrates. In this experiment, a model reaction with caprylic acid and butanol that was catalyzed by lipase from Mucor miehei in alkanes or arenes was employed to investigate the nonthermal effect in nonaqueous enzymatic esterification. With the comparison of the esterification carried by conventional heating and consecutive microwave irradiation, the positive nonthermal effect on the initial reaction rates was found substrate concentration-dependent and could be vanished ostensibly when the substrate concentration was over 2.0 mol L(-1). The polar parameter log P well correlates the solvent polarity with the microwave effect, comparing to dielectric constant and assayed solvatochromic solvent polarity parameters. The log P rule presented in conventional heating-enzymatic esterification still fits in the microwaved enzymatic esterification. Alkanes or arenes with higher log P provided positive nonthermal effect in the range of 2 ≤ log P ≤ 4, but yielded a dramatic decrement after log P = 4. Isomers of same log P with higher dielectric constant received stronger positive nonthermal effect. With lower substrate concentration, the total log P of the reaction mixture has no obvious functional relation with the microwave effect.

  13. Oil palm trunk and sugarcane bagasse derived solid acid catalysts for rapid esterification of fatty acids and moisture-assisted transesterification of oils under pseudo-infinite methanol.

    PubMed

    Ezebor, Francis; Khairuddean, Melati; Abdullah, Ahmad Zuhairi; Boey, Peng Lim

    2014-04-01

    The use of pseudo-infinite methanol in increasing the rate of esterification and transesterification reactions was studied using oil palm trunk (OPT) and sugarcane bagasse (SCB) derived solid acid catalysts. The catalysts were prepared by incomplete carbonisation at 400°C for 8h, followed by sulfonation at 150°C for 15h and characterised using TGA/DTA, XRD, FT-IR, SEM-EDS, EA and titrimetric determinations of acid sites. Under optimal reaction conditions, the process demonstrated rapid esterification of palmitic acid, with FAME yields of 93% and 94% in 45min for OPT and SCB catalysts, respectively. With the process, moisture levels up to 16.7% accelerated the conversion of low FFA oils by sulfonated carbon catalysts, through moisture-induced violent bumping. Moisture assisted transesterification of palm olein containing 1.78% FFA and 8.33% added water gave FAME yield of 90% in 10h, which was two folds over neat oil.

  14. Intermediates to ethylene glycol: carbonylation of formaldehyde catalyzed by Nafion solid perfluorosulfonic acid resin

    SciTech Connect

    Hendriksen, D.E.

    1983-01-01

    Details of a series of reactions for the production of ethylene glycol using a catalyst of Nafion solid perfluorosulfonic acid resin was detailed. The reactions included the carbonylation of formaldehyde and esterification and then hydrogenation of the product of the carbonylation, glycolic acid. Other preparations included in the work included methyl glycolate, acetylglycolic acid, methyl acetylglycolate, and methyl methoxyacetate.

  15. Rh-Catalyzed arylation of fluorinated ketones with arylboronic acids.

    PubMed

    Dobson, Luca S; Pattison, Graham

    2016-09-25

    The Rh-catalyzed arylation of fluorinated ketones with boronic acids is reported. This efficient process allows access to fluorinated alcohols in high yields under mild conditions. Competition experiments suggest that difluoromethyl ketones are more reactive than trifluoromethyl ketones in this process, despite their decreased electronic activation, an effect we postulate to be steric in origin.

  16. Acid-catalyzed dehydrogenation of amine-boranes

    DOEpatents

    Stephens, Frances Helen; Baker, Ralph Thomas

    2010-01-12

    A method of dehydrogenating an amine-borane using an acid-catalyzed reaction. The method generates hydrogen and produces a solid polymeric [R.sup.1R.sup.2B--NR.sup.3R.sup.4].sub.n product. The method of dehydrogenating amine-boranes may be used to generate H.sub.2 for portable power sources.

  17. Esterification of oleic acid with methanol by immobilized lipase on wrinkled silica nanoparticles with highly ordered, radially oriented mesochannels.

    PubMed

    Pang, Jinli; Zhou, Guowei; Liu, Ruirui; Li, Tianduo

    2016-02-01

    Mesoporous silica nanoparticles with a wrinkled structure (wrinkled silica nanoparticles, WSNs) having highly ordered, radially oriented mesochannels were synthesized by a solvothermal method. The method used a mixture of cyclohexane, ethanol, and water as solvent, tetraethoxysilane (TEOS) as source of inorganic silica, ammonium hydroxide as hydrolysis additive, cetyltrimethylammonium bromide (CTAB) as surfactant, and polyvinylpyrrolidone (PVP) as stabilizing agent of particle growth. Particle size (240nm to 540nm), specific surface areas (490m(2)g(-1) to 634m(2)g(-1)), surface morphology (radial wrinkled structures), and pore structure (radially oriented mesochannels) of WSN samples were varied using different molar ratios of CTAB to PVP. Using synthesized WSN samples with radially oriented mesochannels as support, we prepared immobilized Candida rugosa lipase (CRL) as a new biocatalyst for biodiesel production through the esterification of oleic acid with methanol. These results suggest that WSNs with highly ordered, radially oriented mesochannels have promising applications in biocatalysis, with the highest oleic acid conversion rate of about 86.4% under the optimum conditions. PMID:26652346

  18. Aerobic Copper-Catalyzed O-Methylation with Methylboronic Acid.

    PubMed

    Jacobson, Clare E; Martinez-Muñoz, Noelia; Gorin, David J

    2015-07-17

    The oxidative coupling of alkylboronic acids with oxygen nucleophiles offers a strategy for replacing toxic, electrophilic alkylating reagents. Although the Chan-Lam reaction has been widely applied in the arylation of heteroatom nucleophiles, O-alkylation with boronic acids is rare. We report a Cu-catalyzed nondecarboxylative methylation of carboxylic acids with methylboronic acid that proceeds in air with no additional oxidant. An isotope-labeling study supports an oxidative cross-coupling mechanism, in analogy to that proposed for Chan-Lam arylation. PMID:26111825

  19. Profiles of fatty acids and 7-O-acyl okadaic acid esters in bivalves: can bacteria be involved in acyl esterification of okadaic acid?

    PubMed

    Vale, Paulo

    2010-01-01

    The presence of 7-O-acyl okadaic acid (OA) esters was studied by LC-MS in the digestive glands of blue mussel (Mytilus galloprovincialis) and common cockle (Cerastoderma edule) from Albufeira lagoon, located 20km south of Lisbon. The profile of free and total fatty acids (FA) was analysed using a similar LC separation with a reversed phase C8 column and mass spectrometry detection. In mussel the free FA profile was reflected in the FA esterified to OA, being palmitic acid for instance the most abundant in both cases. In cockle, 7-O-acyl esters with palmitic acid were almost absent and esters with a C16:0 isomer were dominant, followed by esters with C15:1 and C15:0. The cockle free FA profile was similar to mussel, and in accordance with literature findings in bivalves. After hydrolysis, a major difference in the FA profile occurred in both species, presenting a high percentage of a C16:0 isomer. The isomer found in general lipids and bound to OA seemed to be related, presenting similar relative retention times (RRT) to C16:0, differing from expected RRT of monomethyl-branched isomers (iso- or anteiso-). A tentative identification was made with the multimethyl-branched isoprenoid, 4,8,12-trimethyltridecanoic acid (TMTD). TMTD is a product of phytol degradation. This was also suspected when the proportion of this compound in relation to palmitic acid was reduced in vivo in mussels fed a chlorophyll-free diet. Extensive esterification of OA by, among others, phytol-degrading bacteria is discussed as a plausible hypothesis in cockle, but not in mussel, due to the relatively high specific proportion of odd-numbered and branched FA.

  20. Cutinase promotes dry esterification of cotton cellulose.

    PubMed

    Xiaoman, Zhao; Teresa, Matama; Artur, Ribeiro; Carla, Silva; Jing, Wu; Jiajia, Fu; Artur, Cavaco-Paulo

    2016-01-01

    Cutinase from Thermobifida fusca was used to esterify the hydroxyl groups of cellulose with the fatty acids from triolein. Cutinase and triolein were pre-adsorbed on cotton and the reaction proceeded in a dry state during 48 h at 35°C. The cutinase-catalyzed esterification of the surface of cotton fabric resulted in the linkage of the oleate groups to the glycoside units of cotton cellulose. The superficial modification was confirmed by performing ATR-FTIR on treated cotton samples and by MALDI-TOF analysis of the liquors from the treatment of the esterified cotton with a crude cellulase mixture. Modified cotton fabric also showed a significant increase of hydrophobicity. This work proposes a novel bio-based approach to obtain hydrophobic cotton.

  1. Surface esterification of cellulose nanofibers by a simple organocatalytic methodology.

    PubMed

    Avila Ramírez, Jhon Alejandro; Suriano, Camila Juan; Cerrutti, Patricia; Foresti, María Laura

    2014-12-19

    Bacterial cellulose nanofibers were esterified with two short carboxylic acids by means of a simple and novel organic acid-catalyzed route. The methodology proposed relayed on the use of a non-toxic biobased α-hydroxycarboxylic acid as catalyst, and proceeded under moderate reaction conditions in solventless medium. By varying the esterification interval, acetylated and propionized bacterial cellulose nanofibers with degree of substitution (DS) in the 0.02-0.45 range could be obtained. Esterified bacterial cellulose samples were characterized by means of Solid-State CP/MAS (13)C Nuclear Magnetic Resonance spectroscopy (CP/MAS (13)C NMR), Fourier Transform Infrared spectroscopy (FTIR), X-ray Diffraction (XRD), Thermogravimetric Analysis (TGA) and chosen hydrophobicity test assays. TGA results showed that the esterified nanofibers had increased thermal stability, whereas XRD data evidenced that the organocatalytic esterification protocol did not alter their crystallinity. The analysis of the ensuing modified nanofibers by NMR, FTIR, XRD and TGA demonstrated that esterification occurred essentially at the surface of bacterial cellulose microfibrils, something highly desirable for changing their surface hydrophilicity while not affecting their ultrastructure.

  2. Surface esterification of cellulose nanofibers by a simple organocatalytic methodology.

    PubMed

    Avila Ramírez, Jhon Alejandro; Suriano, Camila Juan; Cerrutti, Patricia; Foresti, María Laura

    2014-12-19

    Bacterial cellulose nanofibers were esterified with two short carboxylic acids by means of a simple and novel organic acid-catalyzed route. The methodology proposed relayed on the use of a non-toxic biobased α-hydroxycarboxylic acid as catalyst, and proceeded under moderate reaction conditions in solventless medium. By varying the esterification interval, acetylated and propionized bacterial cellulose nanofibers with degree of substitution (DS) in the 0.02-0.45 range could be obtained. Esterified bacterial cellulose samples were characterized by means of Solid-State CP/MAS (13)C Nuclear Magnetic Resonance spectroscopy (CP/MAS (13)C NMR), Fourier Transform Infrared spectroscopy (FTIR), X-ray Diffraction (XRD), Thermogravimetric Analysis (TGA) and chosen hydrophobicity test assays. TGA results showed that the esterified nanofibers had increased thermal stability, whereas XRD data evidenced that the organocatalytic esterification protocol did not alter their crystallinity. The analysis of the ensuing modified nanofibers by NMR, FTIR, XRD and TGA demonstrated that esterification occurred essentially at the surface of bacterial cellulose microfibrils, something highly desirable for changing their surface hydrophilicity while not affecting their ultrastructure. PMID:25263909

  3. Decomposition of peracetic acid catalyzed by vanadium complexes

    SciTech Connect

    Makarov, A.P.; Gekhman, A.E.; Moiseev, I.I.; Polotryuk, O.Y.

    1986-02-01

    This paper studies the decomposition of peracetic acid (AcOOH) in acetic acid (AcOH) catalyzed by vanadium complexes. It is shown that peractic acid in acetic acid solutions of ammonium anadate decomposes with the predominant formation of 0/sub 2/ and small amounts of CO/sub 2/, the yield of which increases with increasing temperature and peracetic acid concentration. Both reactions proceed without the formation of free radicals in amounts detectable by ESR spectroscopy. The rate of oxygen release under conditions in which the formation of CO/sub 2/ is insignificant obeys a kinetic equation indicating the intermediate formation of a complex between V/sup 5 +/ ions and peracetic acid and the slow conversion of this complex into the observed products.

  4. Characteristics of post-impregnated SBA-15 with 12- Tungstophosphoric acid and its correlation with catalytic activity in selective esterification of glycerol to monolaurate

    NASA Astrophysics Data System (ADS)

    Hoo, P. Y.; Abdullah, A. Z.

    2016-06-01

    Selective esterification of glycerol and lauric acid to monolaurin was conducted using 12-tungstophosphoric acid (HPW) incorporated SBA-15 as catalyst. They were synthesized with HPW loadings of 10-40 wt. % via post impregnation and characterized in terms of surficial and structural characteristic, acidity and morphology. Relatively high lauric acid conversion (up to 95%) and monolaurin yield (53%) were observed while the activity was successfully correlated to the material behaviours, i.e. highly acidic active acid sites within highly uniformed mesopores. The effects of different reaction parameters including reactant ratio (1:1-5:1), catalyst loading (1-5 wt. %) and length of fatty acid were also elucidated. Reduced fatty acid conversion was observed when longer fatty acids were used, thus further strengthen the idea of size selectivity effect provided by the synthesized catalysts.

  5. Novel surface-active oligofructose fatty acid mono-esters by enzymatic esterification.

    PubMed

    van Kempen, Silvia E H J; Boeriu, Carmen G; Schols, Henk A; de Waard, Pieter; van der Linden, Erik; Sagis, Leonard M C

    2013-06-01

    This article describes the synthesis of a series of oligofructose monoesters with fatty acids of different chain length (C8, C12, C16 and C18) to obtain food-grade surfactants with a range of amphiphilicity. Reactions were performed in a mixture of DMSO/Bu(t)OH (10/90 v/v) at 60°C and catalysed by immobilised Candida antarctica lipase B. MALDI-TOF-MS analysis showed that the crude reaction products were mixtures of unmodified oligofructose and mostly mono-esters. The conversion into mono-esters increased with the length of the fatty acid chain, reflecting the specificity of the lipase towards more lipophilic substrates. Reverse phase solid phase extraction was used to fractionate the products, which lead to sufficient purity (>93%) of the fatty acid esters for functionality testing. It was shown that derivatives of longer (C16 and C18) fatty acids were more efficient in lowering surface tension and gave a much higher dilatational modulus than derivatives of the shorter (C8 and C12) fatty acids.

  6. Solvent-free lipase-catalyzed preparation of diacylglycerols.

    PubMed

    Weber, Nikolaus; Mukherjee, Kumar D

    2004-08-25

    Various methods have been applied for the enzymatic preparation of diacylglycerols that are used as dietary oils for weight reduction in obesity and related disorders. Interesterification of rapeseed oil triacylglycerols with commercial preparations of monoacylglycerols, such as Monomuls 90-O18, Mulgaprime 90, and Nutrisoft 55, catalyzed by immobilized lipase from Rhizomucor miehei (Lipozyme RM IM) in vacuo at 60 degrees C led to extensive (from 60 to 75%) formation of diacylglycerols. Esterification of rapeseed oil fatty acids with Nutrisoft, catalyzed by Lipozyme RM in vacuo at 60 degrees C, also led to extensive (from 60 to 70%) formation of diacylglycerols. Esterification of rapeseed oil fatty acids with glycerol in vacuo at 60 degrees C, catalyzed by Lipozyme RM and lipases from Thermomyces lanuginosus (Lipozyme TL IM) and Candida antarctica (lipase B, Novozym 435), also provided diacylglycerols, however, to a lower extent (40-45%). Glycerolysis of rapeseed oil triacylglycerols with glycerol in vacuo at 60 degrees C, catalyzed by Lipozyme TL and Novozym 435, led to diacylglycerols to the extent of esterification of rapeseed oil fatty acids with Monomuls resulted in minor reduction of its activity. The products of esterification of rapeseed oil fatty acids with Monomuls and glycerol yielded upon short-path vacuum distillation residues (diacylglycerol oils) containing 66-70% diacylglycerols.

  7. 4-Dimenthylaminopyridine or Acid-Catalyzed Synthesis of Esters: A Comparison

    ERIC Educational Resources Information Center

    van den Berg, Annemieke W. C.; Hanefeld, Ulf

    2006-01-01

    A set of highly atom-economic experiments was developed to highlight the differences between acid- and base-catalyzed ester syntheses and to introduce the principles of atom economy. The hydrochloric acid-catalyzed formation of an ester was compared with the 4-dimethylaminopyradine-catalyzed ester synthesis.

  8. Esterification and transesterification of greases to fatty acid methyl esters with highly active diphanylammonium salts

    Technology Transfer Automated Retrieval System (TEKTRAN)

    We have conducted an investigation designed to identify alternate catalysts for the production of fatty acid methyl esters (FAME) to be used as biodiesel. Diphenylammonium sulfate (DPAS) and diphenylammonium chloride (DPA-HCl) salts were found to be highly active homogeneous catalysts for the simu...

  9. Chemoselectivity in reactions of esterification.

    PubMed

    Nahmany, Moshe; Melman, Artem

    2004-06-01

    This review is devoted to the problem of chemoselective formation of ester functions in polyfunctional molecules. The review covers most typical approaches to chemoselective acylation of hydroxy groups in molecules containing an amino, mercapto, or another hydroxy functionality as well as chemoselective esterification of di- and polycarboxylic acids.

  10. A biodegradable thermoset polymer made by esterification of citric acid and glycerol.

    PubMed

    Halpern, Jeffrey M; Urbanski, Richard; Weinstock, Allison K; Iwig, David F; Mathers, Robert T; von Recum, Horst A

    2014-05-01

    A new biomaterial, a degradable thermoset polymer, was made from simple, economical, biocompatable monomers without the need for a catalyst. Glycerol and citric acid, nontoxic and renewable reagents, were crosslinked by a melt polymerization reaction at temperatures from 90 to 150°C. Consistent with a condensation reaction, water was determined to be the primary byproduct. The amount of crosslinking was controlled by the reaction conditions, including temperature, reaction time, and ratio between glycerol and citric acid. Also, the amount of crosslinking was inversely proportional to the rate of degradation. As a proof-of-principle for drug delivery applications, gentamicin, an antibiotic, was incorporated into the polymer with preliminary evaluations of antimicrobial activity. The polymers incorporating gentamicin had significantly better bacteria clearing of Staphylococcus aureus compared to non-gentamicin gels for up to 9 days.

  11. A Biodegradable Thermoset Polymer Made by Esterification of Citric Acid and Glycerol

    PubMed Central

    Halpern, Jeffrey M.; Urbanski, Richard; Weinstock, Allison K.; Iwig, David F.; Mathers, Robert T.; von Recum, Horst

    2014-01-01

    A new biomaterial, a degradable thermoset polymer, was made from simple, economical, biocompatable monomers without the need for a catalyst. Glycerol and citric acid, non-toxic and renewable reagents, were crosslinked by a melt polymerization reaction at temperatures from 90-150°C. Consistent with a condensation reaction, water was determined to be the primary byproduct. The amount of crosslinking was controlled by the reaction conditions, including temperature, reaction time, and ratio between glycerol and citric acid. Also, the amount of crosslinking was inversely proportional to the rate of degradation. As a proof-of-principle for drug delivery applications, gentamicin, an antibiotic, was incorporated into the polymer with preliminary evaluations of antimicrobial activity. The polymers incorporating gentamicin had significantly better bacteria clearing of Staphylococcus aureus compared to non-gentamicin gels for up to nine days. PMID:23737239

  12. Synthesis of sulfated titania supported on mesoporous silica using direct impregnation and its application in esterification of acetic acid and n-butanol

    NASA Astrophysics Data System (ADS)

    Wang, Yuhong; Gan, Yunting; Whiting, Roger; Lu, Guanzhong

    2009-09-01

    A new method has been developed for the preparation of sulfated titania (S-TiO 2) supported on mesoporous silica. The use of direct exchange of metal containing precursors for the surfactants in the as-synthesized MCM-41 substrate produced a product with high sulfur content without serious blockage of the pore structure of MCM-41. The pore sizes and volumes of the resultant S-TiO 2/MCM-41 composites were found to vary markedly with the loading of TiO 2. The strong acidic character of the composites obtained was examined by using them as catalysts for the esterification of acetic acid and n-butanol.

  13. Effects of dry method esterification of starch on the degradation characteristics of starch/polylactic acid composites.

    PubMed

    Zuo, Ying Feng; Gu, Jiyou; Qiao, Zhibang; Tan, Haiyan; Cao, Jun; Zhang, Yanhua

    2015-01-01

    Maleic anhydride esterified corn starch was prepared by dry method. Esterified starch/polylactic acid (PLA) biodegradable composite was produced via melt extrusion method with blending maleic anhydride esterified corn starch and PLA. The influence of the dry method esterification of starch on the degradation characteristics of starch/PLA composites was investigated by the natural aging degradation which was soil burial method. Test results of mass loss rate showed that the first 30 days of degradation was mainly starch degradation, and the degradation rate of esterified starch/PLA (ES/PLA) was slower than that of native starch/PLA (NS/PLA). Therefore, the damage degree of ES/PLA on the surface and inside was smaller than that of NS/PLA, and the infrared absorption peak intensities of C-O, C=O and C-H were stronger than that of NS/PLA. With the increasing time of soil burial degradation, the damage degree of NS/PLA and ES/PLA on the exterior and interior were gradually increased, whereas the infrared absorption peak intensities of C-O, C=O and C-H were gradually decreased. The XRD diffraction peak intensity of PLA in composites showed an increased trend at first which was then followed by a decreased one along with the increasing time of soil burial degradation, indicating that the degradation of amorphous regions of PLA was earlier than its crystalline regions. When the soil burial time was the same, the diffraction peak intensity of PLA in ES/PLA was stronger than that of NS/PLA. If the degradation time was the same, T0, Ti and residual rate of thermal decomposition of NS/PLA were larger than those of ES/PLA. The tensile strength and bending strength of composites were decreased gradually with soil burial time increasing. Both the tensile strength and bending strength of ES/PLA were stronger than those of NS/PLA.

  14. Solvent effects in acid-catalyzed biomass conversion reactions.

    PubMed

    Mellmer, Max A; Sener, Canan; Gallo, Jean Marcel R; Luterbacher, Jeremy S; Alonso, David Martin; Dumesic, James A

    2014-10-27

    Reaction kinetics were studied to quantify the effects of polar aprotic organic solvents on the acid-catalyzed conversion of xylose into furfural. A solvent of particular importance is γ-valerolactone (GVL), which leads to significant increases in reaction rates compared to water in addition to increased product selectivity. GVL has similar effects on the kinetics for the dehydration of 1,2-propanediol to propanal and for the hydrolysis of cellobiose to glucose. Based on results obtained for homogeneous Brønsted acid catalysts that span a range of pKa values, we suggest that an aprotic organic solvent affects the reaction kinetics by changing the stabilization of the acidic proton relative to the protonated transition state. This same behavior is displayed by strong solid Brønsted acid catalysts, such as H-mordenite and H-beta. PMID:25214063

  15. Esterification of free fatty acids in adipocytes: a comparison between octanoate and oleate.

    PubMed

    Guo, W; Choi, J K; Kirkland, J L; Corkey, B E; Hamilton, J A

    2000-07-15

    Medium-chain triacylglycerols (MCT) are present in milk, coconut oil and other foods, and are used therapeutically in special diets for certain disorders of lipid and glucose utilization. Recently, it has become apparent that MCT are not only oxidized in the liver, but are also present in lymph and fat tissue, particularly after chronic treatment. To evaluate the influence of MCT on metabolism in fat cells, we compared incorporation of octanoate and oleate into cellular triacylglycerols of 3T3-L1 adipocytes as well as their effects on preadipocyte differentiation. We found that less octanoate than oleate was stored and that more octanoate than oleate was oxidized. Octanoate was esterified to a greater extent at the sn-1,3 position of glyceryl carbons than at the sn-2 position, whereas the opposite was true for oleate. Glycerol release from fat cells pre-treated with octanoate was also greater than from cells pre-treated with oleate, presumably related to the preferential release of octanoate from the sn-1,3 position. Octanoate was not incorporated into lipids in undifferentiated cells and did not induce differentiation in these cells, whereas oleate was readily stored and actually induced differentiation. Incorporation of octanoate into lipids increased as cells differentiated, but reached a maximum of about 10% of the total stored fatty acids. If these effects in vitro also occur in vivo, substitution of octanoate for oleate or other long-chain fatty acids could have the beneficial effect of diminishing fat-cell number and lipid content. PMID:10880345

  16. Esterification of polyglycerol with polycondensed ricinoleic acid catalysed by immobilised Rhizopus oryzae lipase.

    PubMed

    Ortega, S; Máximo, M F; Montiel, M C; Murcia, M D; Arnold, G; Bastida, J

    2013-09-01

    The enzymatic method for synthesising polyglycerol polyricinoleate (PGPR), a food additive named E-476, was successfully carried out in the presence of immobilised Rhizopus oryzae lipase in a solvent-free medium. The great advantage of using the commercial preparation of R. oryzae lipase is that it is ten times cheaper than the commercial preparation of R. arrhizus lipase, the biocatalyst used in previous studies. The reaction, which is really a reversal of hydrolysis, takes place in the presence of a very limited amount of aqueous phase. Immobilisation of the lipase by physical adsorption onto an anion exchange resin provided good results in terms of activity, enzyme stability and reuse of the immobilised derivative. It has been established that the adsorption of R. oryzae lipase on Lewatit MonoPlus MP 64 follows a pseudo-second order kinetics, which means that immobilisation is a process of chemisorption, while the equilibrium adsorption follows a Langmuir isotherm. The use of this immobilised derivative as catalyst for obtaining PGPR under a controlled atmosphere in a vacuum reactor, with a dry nitrogen flow intake, allowed the synthesis of a product with an acid value lower than 6 mg KOH/g, which complies with the value established by the European Commission Directive. This product also fulfils the European specifications regarding the hydroxyl value and refractive index given for this food additive, one of whose benefits, as proved in our experiments, is that it causes a drastic decrease in the viscosity (by 50 %) and yield stress (by 82 %) of chocolate, comparable to the impact of customary synthesised PGPR.

  17. Synthesis of aliphatic esters of cinnamic acid as potential lipophilic antioxidants catalyzed by lipase B from Candida antarctica.

    PubMed

    Jakovetić, Sonja M; Jugović, Branimir Z; Gvozdenović, Milica M; Bezbradica, Dejan I; Antov, Mirjana G; Mijin, Dušan Z; Knežević-Jugović, Zorica D

    2013-08-01

    Immobilized lipase from Candida antarctica (Novozyme 435) was tested for the synthesis of various phenolic acid esters (ethyl and n-butyl cinnamate, ethyl p-coumarate and n-butyl p-methoxycinnamate). The second-order kinetic model was used to mathematically describe the reaction kinetics and to compare present processes quantitatively. It was found that the model agreed well with the experimental data. Further, the effect of alcohol type on the esterification of cinnamic acid was investigated. The immobilized lipase showed more ability to catalyze the synthesis of butyl cinnamate. Therefore, the process was optimized for the synthesis of butyl cinnamate as a function of solvent polarity (logP) and amount of biocatalyst. The highest ester yield of 60.7 % was obtained for the highest enzyme concentration tested (3 % w/w), but the productivity was for 34 % lower than the corresponding value obtained for the enzyme concentration of 1 % (w/w). The synthesized esters were purified, identified, and screened for antioxidant activities. Both DPPH assay and cyclic voltammetry measurement have shown that cinnamic acid esters have better antioxidant properties than cinnamic acid itself.

  18. Methods and catalysts for making biodiesel from the transesterification and esterification of unrefined oils

    DOEpatents

    Yan, Shuli; Salley, Steven O.; Ng, K. Y. Simon

    2012-04-24

    A method of forming a biodiesel product and a heterogeneous catalyst system used to form said product that has a high tolerance for the presence of water and free fatty acids (FFA) in the oil feedstock is disclosed. This catalyst system may simultaneously catalyze both the esterification of FAA and the transesterification of triglycerides present in the oil feedstock. The catalyst system according to one aspect of the present disclosure represents a class of zinc and lanthanum oxide heterogeneous catalysts that include different ratios of zinc oxide to lanthanum oxides (Zn:La ratio) ranging from about 10:0 to 0:10. The Zn:La ratio in the catalyst is believed to have an effect on the number and reactivity of Lewis acid and base sites, as well as the transesterification of glycerides, the esterification of fatty acids, and the hydrolysis of glycerides and biodiesel.

  19. Borinic Acid Catalyzed Stereo- and Regioselective Couplings of Glycosyl Methanesulfonates.

    PubMed

    D'Angelo, Kyan A; Taylor, Mark S

    2016-08-31

    In the presence of a diarylborinic acid catalyst, glycosyl methanesulfonates engage in regio- and stereoselective couplings with partially protected pyranoside and furanoside acceptors. The methanesulfonate donors are prepared in situ from glycosyl hemiacetals, and are coupled under mild, operationally simple conditions (amine base, organoboron catalyst, room temperature). The borinic acid catalyst not only influences site-selectivity via activation of 1,2- or 1,3-diol motifs, but also has a pronounced effect on the stereochemical outcome: 1,2-trans-linked disaccharides are obtained selectively in the absence of neighboring group participation. Reaction progress kinetic analysis was used to obtain insight into the mechanism of glycosylation, both in the presence of catalyst and in its absence, while rates of interconversion of methanesulfonate anomers were determined by NMR exchange spectroscopy (EXSY). Together, the results suggest that although the uncatalyzed and catalyzed reactions give rise to opposite stereochemical outcomes, both proceed by associative mechanisms. PMID:27533523

  20. Hydrolysis of cellulose catalyzed by novel acidic ionic liquids.

    PubMed

    Zhuo, Kelei; Du, Quanzhou; Bai, Guangyue; Wang, Congyue; Chen, Yujuan; Wang, Jianji

    2015-01-22

    The conversion of cellulosic biomass directly into valuable chemicals becomes a hot subject. Six novel acidic ionic liquids (ILs) based on 2-phenyl-2-imidazoline were synthesized and characterized by UV-VIS, TGA, and NMR. The novel acidic ionic liquids were investigated as catalysts for the hydrolysis of cellulose in 1-butyl-3-methylimidazolium chloride ([Bmim]Cl). The acidic ionic liquids with anions HSO4(-) and Cl(-) showed better catalytic performance for the hydrolysis of cellulose than those with H2PO4(-). The temperature and dosage of water affect significantly the yield of total reducing sugar (TRS). When the hydrolysis of cellulose was catalyzed by 1-propyl sulfonic acid-2-phenyl imidazoline hydrogensulfate (IL-1) and the dosage of water was 0.2g, the TRS yield was up to 85.1% within 60 min at 100°C. These new acidic ionic liquids catalysts are expected to have a wide application in the conversion of cellulose into valuable chemicals. PMID:25439867

  1. Greater Transport Efficiencies of the Membrane Fatty Acid Transporters FAT/CD36 and FATP4 Compared with FABPpm and FATP1 and Differential Effects on Fatty Acid Esterification and Oxidation in Rat Skeletal Muscle*

    PubMed Central

    Nickerson, James G.; Alkhateeb, Hakam; Benton, Carley R.; Lally, James; Nickerson, Jennifer; Han, Xiao-Xia; Wilson, Meredith H.; Jain, Swati S.; Snook, Laelie A.; Glatz, Jan F. C.; Chabowski, Adrian; Luiken, Joost J. F. P.; Bonen, Arend

    2009-01-01

    In selected mammalian tissues, long chain fatty acid transporters (FABPpm, FAT/CD36, FATP1, and FATP4) are co-expressed. There is controversy as to whether they all function as membrane-bound transporters and whether they channel fatty acids to oxidation and/or esterification. Among skeletal muscles, the protein expression of FABPpm, FAT/CD36, and FATP4, but not FATP1, correlated highly with the capacities for oxidative metabolism (r ≥ 0.94), fatty acid oxidation (r ≥ 0.88), and triacylglycerol esterification (r ≥ 0.87). We overexpressed independently FABPpm, FAT/CD36, FATP1, and FATP4, within a normal physiologic range, in rat skeletal muscle, to determine the effects on fatty acid transport and metabolism. Independent overexpression of each fatty acid transporter occurred without altering either the expression or plasmalemmal content of other fatty acid transporters. All transporters increased fatty acid transport, but FAT/CD36 and FATP4 were 2.3- and 1.7-fold more effective than FABPpm and FATP1, respectively. Fatty acid transporters failed to alter the rates of fatty acid esterification into triacylglycerols. In contrast, all transporters increased the rates of long chain fatty acid oxidation, but the effects of FABPpm and FAT/CD36 were 3-fold greater than for FATP1 and FATP4. Thus, fatty acid transporters exhibit different capacities for fatty acid transport and metabolism. In vivo, FAT/CD36 and FATP4 are the most effective fatty acid transporters, whereas FABPpm and FAT/CD36 are key for stimulating fatty acid oxidation. PMID:19380575

  2. Extensive esterification of adrenal C19-delta 5-sex steroids to long-chain fatty acids in the ZR-75-1 human breast cancer cell line

    SciTech Connect

    Poulin, R.; Poirier, D.; Merand, Y.; Theriault, C.; Belanger, A.; Labrie, F.

    1989-06-05

    Estrogen-sensitive human breast cancer cells (ZR-75-1) were incubated with the 3H-labeled adrenal C19-delta 5-steroids dehydroepiandrosterone (DHEA) and its fully estrogenic derivative, androst-5-ene-3 beta,17 beta-diol (delta 5-diol) for various time intervals. When fractionated by solvent partition, Sephadex LH-20 column chromatography and silica gel TLC, the labeled cell components were largely present (40-75%) in three highly nonpolar, lipoidal fractions. Mild alkaline hydrolysis of these lipoidal derivatives yielded either free 3H-labeled DHEA or delta 5-diol. The three lipoidal fractions cochromatographed with the synthetic DHEA 3 beta-esters, delta 5-diol 3 beta (or 17 beta)-monoesters and delta 5-diol 3 beta,17 beta-diesters of long-chain fatty acids. DHEA and delta 5-diol were mainly esterified to saturated and mono-unsaturated fatty acids. For delta 5-diol, the preferred site of esterification of the fatty acids is the 3 beta-position while some esterification also takes place at the 17 beta-position. Time course studies show that ZR-75-1 cells accumulate delta 5-diol mostly (greater than 95%) as fatty acid mono- and diesters while DHEA is converted to delta 5-diol essentially as the esterified form. Furthermore, while free C19-delta 5-steroids rapidly diffuse out of the cells after removal of the precursor (3H)delta 5-diol, the fatty acid ester derivatives are progressively hydrolyzed, and DHEA and delta 5-diol thus formed are then sulfurylated prior to their release into the culture medium. The latter process however is rate-limited, since new steady-state levels of free steroids and fatty acid esters are rapidly reached and maintained for extended periods of time after removal of precursor, thus maintaining minimal concentrations of intracellular steroids.

  3. Catalysis by heteropoly compounds. XXII. Reactions of esters and esterification catalyzed by heteropolyacids in a homogeneous liquid phase - effects of the central atom of heteropolyanions having tungsten as the addenda atom

    SciTech Connect

    Hu, Changwen; Hashimoto, Masato; Okuhara, Toshio; Misono, Makoto )

    1993-10-01

    Decomposition of isobutyl propionate (IBP) (Reaction (1)), ester exchange of IBP with acetic acid (Reaction (2)), ester exchange of IBP with n-propyl alcohol (Reaction (3)), and esterification of propionic acid with isobutyl alcohol (Reaction (4)) have been studied in a homogeneous liquid phase using heteropolyacids H[sub m]XW[sub 12]O[sub 40] (X = P, Si, Ge, B, and Co) having the Keggin structure and H[sub 6]P[sub 2]W[sub 18]O[sub 62] having the Dawson structure. The results clearly indicated that the catalytic behavior of heteropolyacids remarkably depended on the kind of reaction system, namely, the basicity of reactants. For Reaction (1), the catalytic activities of the heteropolyacids were 60-100 times higher than those of H[sub 2]SO[sub 4] and p-toluenesulfonic acid. Among the heteropolyacids, the activity was in the order H[sub 3]PW[sub 12]O[sub 40] > H[sub 4]SiW[sub 12]O[sub 40] [approximately] H[sub 4]GeW[sub 12]O[sub 40] > H[sub 5]BW[sub 12]O[sub 40] > H[sub 6]CoW[sub 12]O[sub 40]. This order suggests that the activity follows the order of the acid strength of the solutions of heteropolyacids, which increases with the decrease in the negative charge of the polyanion. H[sub 6]P[sub 2]W[sub 18]O[sub 62] showed an activity between those of H[sub 5]BW[sub 12]O[sub 40] and H[sub 6]CoW[sub 12]O[sub 40]. Water molecules in the system retarded Reaction 1. For Reaction 2, the activity order was similar to that for Reaction 1 in the absence of water. However, contrary to Reaction 1, the addition of water greatly accelerated Reaction 2. It was presumed that, in the presence of water, Reaction 2 proceeds via the hydrolysis of IBP to propionic acid and isobutyl alcohol, followed by the esterification of isobutyl alcohol with acetic acid. 28 refs., 8 figs., 4 tabs.

  4. Acid-Catalyzed Preparation of Biodiesel from Waste Vegetable Oil: An Experiment for the Undergraduate Organic Chemistry Laboratory

    ERIC Educational Resources Information Center

    Bladt, Don; Murray, Steve; Gitch, Brittany; Trout, Haylee; Liberko, Charles

    2011-01-01

    This undergraduate organic laboratory exercise involves the sulfuric acid-catalyzed conversion of waste vegetable oil into biodiesel. The acid-catalyzed method, although inherently slower than the base-catalyzed methods, does not suffer from the loss of product or the creation of emulsion producing soap that plagues the base-catalyzed methods when…

  5. SulE, a sulfonylurea herbicide de-esterification esterase from Hansschlegelia zhihuaiae S113.

    PubMed

    Hang, Bao-Jian; Hong, Qing; Xie, Xiang-Ting; Huang, Xing; Wang, Cheng-Hong; He, Jian; Li, Shun-Peng

    2012-03-01

    De-esterification is an important degradation or detoxification mechanism of sulfonylurea herbicide in microbes and plants. However, the biochemical and molecular mechanisms of sulfonylurea herbicide de-esterification are still unknown. In this study, a novel esterase gene, sulE, responsible for sulfonylurea herbicide de-esterification, was cloned from Hansschlegelia zhihuaiae S113. The gene contained an open reading frame of 1,194 bp, and a putative signal peptide at the N terminal was identified with a predicted cleavage site between Ala37 and Glu38, resulting in a 361-residue mature protein. SulE minus the signal peptide was synthesized in Escherichia coli BL21 and purified to homogeneity. SulE catalyzed the de-esterification of a variety of sulfonylurea herbicides that gave rise to the corresponding herbicidally inactive parent acid and exhibited the highest catalytic efficiency toward thifensulfuron-methyl. SulE was a dimer without the requirement of a cofactor. The activity of the enzyme was completely inhibited by Ag(+), Cd(2+), Zn(2+), methamidophos, and sodium dodecyl sulfate. A sulE-disrupted mutant strain, ΔsulE, was constructed by insertion mutation. ΔsulE lost the de-esterification ability and was more sensitive to the herbicides than the wild type of strain S113, suggesting that sulE played a vital role in the sulfonylurea herbicide resistance of the strain. The transfer of sulE into Saccharomyces cerevisiae BY4741 conferred on it the ability to de-esterify sulfonylurea herbicides and increased its resistance to the herbicides. This study has provided an excellent candidate for the mechanistic study of sulfonylurea herbicide metabolism and detoxification through de-esterification, construction of sulfonylurea herbicide-resistant transgenic crops, and bioremediation of sulfonylurea herbicide-contaminated environments.

  6. Metal ion-catalyzed nucleic acid alkylation and fragmentation.

    PubMed

    Browne, Kenneth A

    2002-07-10

    Nucleic acid microarrays are a growing technology in which high densities of known sequences are attached to a substrate in known locations (addressed). Hybridization of complementary sequences leads to a detectable signal such as an electrical impulse or fluorescence. This combination of sequence addressing, hybridization, and detection increases the efficiency of a variety of genomic disciplines including those that profile genetic expression, search for single nucleotide polymorphisms (SNPs), or diagnose infectious diseases by sequencing portions of microbial or viral genomes. Incorporation of reporter molecules into nucleic acids is essential for the sensitive detection of minute amounts of nucleic acids on most types of microarrays. Furthermore, polynucleic acid size reduction increases hybridization because of increased diffusion rates and decreased competing secondary structure of the target nucleic acids. Typically, these reactions would be performed as two separate processes. An improvement to past techniques, termed labeling-during-cleavage (LDC), is presented in which DNA or RNA is alkylated with fluorescent tags and fragmented in the same reaction mixture. In model studies with 26 nucleotide-long RNA and DNA oligomers using ultraviolet/visible and fluorescence spectroscopies as well as high-pressure liquid chromatography and mass spectrometry, addition of both alkylating agents (5-(bromomethyl)fluorescein, 5- or 6-iodoacetamidofluorescein) and select metal ions (of 21 tested) to nucleic acids in aqueous solutions was critical for significant increases in both labeling and fragmentation, with >or=100-fold increases in alkylation possible relative to metal ion-free reactions. Lanthanide series metal ions, Pb(2+), and Zn(2+) were the most reactive ions in terms of catalyzing alkylation and fragmentation. While oligonucleotides were particularly susceptible to fragmentation at sites containing phosphorothioate moieties, labeling and cleavage reactions

  7. Lewis Acid-Catalyzed Indole Synthesis via Intramolecular Nucleophilic Attack of Phenyldiazoacetates to Iminium Ions

    PubMed Central

    Zhou, Lei; Doyle, Michael P.

    2009-01-01

    Lewis acids catalyze the cyclization of methyl phenyldiazoacetates with an ortho-imino group, prepared from o-aminophenylacetic acid, to give 2,3-substituted indoles in quantitative yields. PMID:19904905

  8. Metabolic regulation of fatty acid esterification and effects of conjugated linoleic acid on glucose homeostasis in pig hepatocytes.

    PubMed

    Conde-Aguilera, J A; Lachica, M; Nieto, R; Fernández-Fígares, I

    2012-02-01

    Conjugated linoleic acids (CLAs) are geometric and positional isomers of linoleic acid (LA) that promote growth, alter glucose metabolism and decrease body fat in growing animals, although the mechanisms are poorly understood. A study was conducted to elucidate the effects of CLA on glucose metabolism, triglyceride (TG) synthesis and IGF-1 synthesis in primary culture of porcine hepatocytes. In addition, hormonal regulation of TG and IGF-1 synthesis was addressed. Hepatocytes were isolated from piglets (n = 5, 16.0 ± 1.98 kg average body weight) by collagenase perfusion and seeded into collagen-coated T-25 flasks. Hepatocytes were cultured in William's E containing dexamethasone (10-8 and 10-7 M), insulin (10 and 100 ng/ml), glucagon (0 and 100 ng/ml) and CLA (1 : 1 mixture of cis-9, trans-11 and trans-10, cis-12 CLA, 0.05 and 0.10 mM) or LA (0.05 and 0.10 mM). Addition of CLA decreased gluconeogenesis (P < 0.05), whereas glycogen synthesis and degradation, TG synthesis and IGF-1 synthesis were not affected compared with LA. Increased concentration of fatty acids in the media decreased IGF-1 production (P < 0.001) and glycogen synthesis (P < 0.01), and increased gluconeogenesis (P < 0.001) and TG synthesis (P < 0.001). IGF-1 synthesis increased (P < 0.001) and TG synthesis decreased (P < 0.001) as dexamethasone concentration in the media rose. High insulin/glucagon increased TG synthesis. These results indicate that TG synthesis in porcine hepatocytes is hormonally regulated so that dexamethasone decreases and insulin/glucagon increases it. In addition, CLA decreases hepatic glucose production through decreased gluconeogenesis.

  9. Diacylglycerol and triacylglycerol as responses in a dual response surface-optimized process for diacylglycerol production by lipase-catalyzed esterification in a pilot packed-bed enzyme reactor.

    PubMed

    Lo, Seong-Koon; Cheong, Ling-Zhi; Arifin, Norlelawati; Tan, Chin-Ping; Long, Kamariah; Yusoff, Mohd Suria Affandi; Lai, Oi-Ming

    2007-07-11

    Diacylglycerol (DAG) and triacylglycerol (TAG) as responses on optimization of DAG production using a dual response approach of response surface methodology were investigated. This approach takes the molecular equilibrium of DAG into account and allows for the optimization of reaction conditions to achieve maximum DAG and minimum TAG yields. The esterification reaction was optimized with four factors using a central composite rotatable design. The following optimized conditions yielded 48 wt % DAG and 14 wt % TAG: reaction temperature of 66.29 degrees C, enzyme dosage of 4 wt %, fatty acid/glycerol molar ratio of 2.14, and reaction time of 4.14 h. Similar results were achieved when the process was scaled up to a 10 kg production in a pilot packed-bed enzyme reactor. Lipozyme RM IM did not show any significant activity losses or changes in fatty acid selectivity on DAG synthesis during the 10 pilot productions. However, lipozyme RM IM displayed higher selectivity toward the production of oleic acid-enriched DAG. The purity of DAG oil after purification was 92 wt %.

  10. Hydrolysis and esterification in organically modified alkoxysilanes: A {sup 29}Si NMR investigation of methyltrimethoxysilane

    SciTech Connect

    Alam, T.M.; Assink, R.A.; Loy, D.A.

    1996-09-01

    High-resolution {sup 29}Si NMR was used to investigate the acid-catalyzed hydrolysis and esterification reactions of methyltrimethoxysilane (MTMS) in methanol. The INEPT experiment, adapted for spin systems with multiple heteronuclear coupling constants, was used to assign the closely spaced resonances of the MTMS hydrolysis products. Due to the rapid reaction rates, only the pseudoequilibrium concentration distributions for the resulting hydrolysis products could be determined. Models based on thermodynamically statistical distributions, irreversible hydrolysis reactions, and reversible hydrolysis reactions were nearly equally successful in accounting for the concentration distributions over a wide range of H{sub 2}O/Si ratios (R{sub w}) and temperatures. However, preparation of hydrolyzed MTMS in a nonpseudoequilibrium state unequivocally demonstrated the reversibility of hydrolysis reactions on a short time scale. By measuring the extent of reaction of MTMS systems at high water concentrations, the ratio of the hydrolysis to esterification rate constant was determined to be approximately 100. 36 refs., 7 figs.

  11. Use of a palladium(II)-catalyzed oxidative kinetic resolution in synthetic efforts toward bielschowskysin

    PubMed Central

    Meyer, Michael E.; Phillips, John H.; Ferreira, Eric M.; Stoltz, Brian M.

    2013-01-01

    Progress toward the cyclobutane core of bielshowskysin is reported. The core was thought to arise from a cyclopropane intermediate via a furan-mediated cyclopropane fragmentation, followed by a 1,4-Michael addition. The synthesis of the cyclopropane intermediate utilizes a Suzuki coupling reaction, an esterification with 2-diazoacetoacetic acid, and a copper catalyzed cyclopropanation. An alcohol intermediate within the synthetic route was obtained in high enantiopurity via a highly selective palladium(II)-catalyzed oxidative kinetic resolution (OKR). PMID:23913988

  12. Template-free synthesis of a porous organic-inorganic hybrid tin(IV) phosphonate and its high catalytic activity for esterification of free fatty acids.

    PubMed

    Dutta, Arghya; Patra, Astam K; Uyama, Hiroshi; Bhaumik, Asim

    2013-10-23

    Here we have synthesized an organic-inorganic hybrid mesoporous tin phosphonate monolith (MLSnP-1) with crystalline pore walls by a template-free sol-gel route. N2 sorption analysis shows Brunauer-Emmett-Teller (BET) surface area of 347 m2 g(-1). Wide-angle powder X-ray diffraction (PXRD) pattern shows few broad diffraction peaks indicating crystalline pore wall of the material. High-resolution transmission electron microscopic (HR TEM) image further reveals the crystal fringes on the pore wall. Framework bonding and local environment around phosphorus and carbon were examined by Fourier transform infrared (FT IR) spectroscopy and solid-state MAS NMR spectroscopy. The material exhibits remarkable catalytic activity for esterification of long chain fatty acids under mild reaction conditions at room temperature.

  13. Theoretical study of water cluster catalyzed decomposition of formic acid.

    PubMed

    Inaba, Satoshi

    2014-04-24

    We have performed a number of quantum chemical simulations to examine water cluster catalyzed decomposition of formic acid. The decomposition of formic acid consists of two competing pathways, dehydration, and decarboxylation. We use the Gaussian 4 method of the Gaussian09 software to locate and optimize a transition state of the decomposition reaction and obtain the activation energy. The decomposition starts by transferring a proton of a formic acid to a water molecule. The de Broglie wavelength of a proton is similar to the width of the potential barrier of the decomposition reaction at low temperature. The tunneling, in which a proton penetrates the potential barrier, enhances the decomposition rate. Water molecules serve as the catalyst in the decomposition and reduce the activation energy. The relay of a proton from a water molecule to a neighboring water molecule is accomplished with little change of the geometry of a molecule, resulting in the reduction of the activation energy. Two water molecules are actively involved in the decomposition reaction to reduce the activation energy. We have also examined the effect of water clusters with three, four, and five water molecules on the decomposition reaction. The noncovalent distance between a hydrogen atom of a water molecule and an oxygen atom of a neighboring water molecule decreases in a water cluster due to the cooperative many-body interactions. A water molecule in a water cluster becomes a better proton donor as well as a better proton acceptor. The activation energy of the decomposition is further decreased by the catalytic effect of a water cluster. We calculate the reaction rate using the transition state theory corrected by the tunneling effect of a proton. The calculated reaction rate of the decarboxylation is smaller than that of the dehydration when less than three water molecules are included in the simulation. However, the major product of the decomposition of a formic acid becomes carbon dioxide

  14. Efficient and simple approaches towards direct oxidative esterification of alcohols.

    PubMed

    Ray, Ritwika; Jana, Rahul Dev; Bhadra, Mayukh; Maiti, Debabrata; Lahiri, Goutam Kumar

    2014-11-17

    The present article describes novel oxidative protocols for direct esterification of alcohols. The protocols involve successful demonstrations of both "cross" and "self" esterification of a wide variety of alcohols. The cross-esterification proceeds under a simple transition-metal-free condition, containing catalytic amounts of TEMPO (2,2,6,6-tetramethyl-1-piperidinyloxy)/TBAB (tetra-n-butylammonium bromide) in combination with oxone (potassium peroxo monosulfate) as the oxidant, whereas the self-esterification is achieved through simple induction of Fe(OAc)2 /dipic (dipic=2,6-pyridinedicarboxylic acid) as the active catalyst under an identical oxidizing environment.

  15. Integrated Production of Xylonic Acid and Bioethanol from Acid-Catalyzed Steam-Exploded Corn Stover.

    PubMed

    Zhu, Junjun; Rong, Yayun; Yang, Jinlong; Zhou, Xin; Xu, Yong; Zhang, Lingling; Chen, Jiahui; Yong, Qiang; Yu, Shiyuan

    2015-07-01

    High-efficiency xylose utilization is one of the restrictive factors of bioethanol industrialization. However, xylonic acid (XA) as a new bio-based platform chemical can be produced by oxidation of xylose with microbial. So, an applicable technology of XA bioconversion was integrated into the process of bioethanol production. After corn stover was pretreated with acid-catalyzed steam-explosion, solid and liquid fractions were obtained. The liquid fraction, also named as acid-catalyzed steam-exploded corn stover (ASC) prehydrolyzate (mainly containing xylose), was catalyzed with Gluconobacter oxydans NL71 to prepare XA. After 72 h of bioconversion of concentrated ASC prehydrolyzate (containing 55.0 g/L of xylose), the XA concentration reached a peak value of 54.97 g/L, the sugar utilization ratio and XA yield were 94.08 and 95.45 %, respectively. The solid fraction was hydrolyzed to produce glucose with cellulase and then fermented with Saccharomyces cerevisiae NL22 to produce ethanol. After 18 h of fermentation of concentrated enzymatic hydrolyzate (containing 86.22 g/L of glucose), the ethanol concentration reached its highest value of 41.48 g/L, the sugar utilization ratio and ethanol yield were 98.72 and 95.25 %, respectively. The mass balance showed that 1 t ethanol and 1.3 t XA were produced from 7.8 t oven dry corn stover.

  16. Optimizing the Acid Catalyzed Synthesis of Hyperbranched Poly(Glycerol-diacids) Oligomers

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Oligomeric pre-polymers were synthesized by the acid-catalyzed condensation of glycerol with succinic acid, glutaric acid and azelaic acid in dimethylsulfoxide (DMSO) or dimethylformamide (DMF). The prepolymers were obtained, on average in 84% yield, and were characterized by proton NMR, MALDI-TOF ...

  17. The Lewis acid catalyzed synthesis of hyperbranched Oligo(glycerol-diacid)s in aprotic polar media

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The Lewis-acid, titanium (IV) butoxide (15% (w/w; catalyst/reactants)), was used to catalyze the condensation of 0.05 mol glycerol with 0.10 mol of either succinic acid, glutaric acid, or azelaic acid to produce oligomers. The reactions were refluxed in dilute solutions of dimethylsulfoxide (DMSO) o...

  18. The BioC O-Methyltransferase Catalyzes Methyl Esterification of Malonyl-Acyl Carrier Protein, an Essential Step in Biotin Synthesis*

    PubMed Central

    Lin, Steven; Cronan, John E.

    2012-01-01

    Recent work implicated the Escherichia coli BioC protein as the initiator of the synthetic pathway that forms the pimeloyl moiety of biotin (Lin, S., Hanson, R. E., and Cronan, J. E. (2010) Nat. Chem. Biol. 6, 682–688). BioC was believed to be an O-methyltransferase that methylated the free carboxyl of either malonyl-CoA or malonyl-acyl carrier protein based on the ability of O-methylated (but not unmethylated) precursors to bypass the BioC requirement for biotin synthesis both in vivo and in vitro. However, only indirect proof of the hypothesized enzymatic activity was obtained because the activities of the available BioC preparations were too low for direct enzymatic assay. Because E. coli BioC protein was extremely recalcitrant to purification in an active form, BioC homologues of other bacteria were tested. We report that the native form of Bacillus cereus ATCC10987 BioC functionally replaced E. coli BioC in vivo, and the protein could be expressed in soluble form and purified to homogeneity. In disagreement with prior scenarios that favored malonyl-CoA as the methyl acceptor, malonyl-acyl carrier protein was a far better acceptor of methyl groups from S-adenosyl-l-methionine than was malonyl-CoA. BioC was specific for the malonyl moiety and was inhibited by S-adenosyl-l-homocysteine and sinefungin. High level expression of B. cereus BioC in E. coli blocked cell growth and fatty acid synthesis. PMID:22965231

  19. Pentafluorobenzyl esterification of haloacetic acids in tap water for simple and sensitive analysis by gas chromatography/mass spectrometry with negative chemical ionization.

    PubMed

    Zhao, Can; Fujii, Yukiko; Yan, Junxia; Harada, Kouji H; Koizumi, Akio

    2015-01-01

    Chlorine is the most widely used disinfectant for control of waterborne diseases in drinking water treatment. It can react with natural organic matter in water and form haloacetic acids (HAAs). For analysis of HAA levels, derivatization with diazomethane is commonly recommended as the standard methodology in Japan. However, diazomethane is a carcinogenic alkylating agent. Therefore, in this study, a safe, simple, and sensitive quantification method was developed to monitor HAAs in drinking water. Pentafluorobenzyl esterification was used for pretreatment. The pentafluorobenzyl-ester derivative was detected by gas chromatography-negative ion chemical ionization-mass spectrometry analysis with very high sensitivity for HAAs analysis. The method has low detection limits (8-94 ng L(-1)) and good recovery rates (89-99%) for HAAs. The method was applied to 30 tap water samples from 15 cities in the Kansai region of Japan. The levels of HAAs detected were in the range 0.54-7.83 μg L(-1). Dichloroacetic acid, trichloroacetic acid, and bromochloroacetic acid were the major HAAs detected in most of the tap water, and accounted for 29%, 20% and 19% of the total HAAs, respectively. This method could be used for routine monitoring of HAAs in drinking water without exposure of workers to occupational hazards.

  20. Highly chemoselective methylation and esterification reactions with dimethyl carbonate in the presence of NaY faujasite. The case of mercaptophenols, mercaptobenzoic acids, and carboxylic acids bearing OH substituents.

    PubMed

    Selva, Maurizio; Tundo, Pietro

    2006-02-17

    In the presence of NaY faujasite, the reactions of dimethyl carbonate (DMC) with several ambident nucleophiles such as o- and p-mercaptophenols (1a,b), o- and p-mercaptobenzoic acids (2a,b), o- and p-hydroxybenzoic acids (3a,b), mandelic and phenyllactic acids (4, 5), have been explored under batch conditions. Highly chemoselective reactions can be performed: at 150 degrees C, compounds 1 and 2 undergo only a S-methylation reaction, without affecting OH and CO2H groups; at 165 degrees C, acids 3-5 form the corresponding methyl esters, while both their aromatic and aliphatic OH substituents are fully preserved from methylation and/or transesterification processes. Typical selectivities are of 90-98% and isolated yields of products (S-methyl derivatives and methyl esters, respectively) are in the range of 85-96%. A comparative study with K2CO3 as a catalyst is also reported. Although the base (K2CO3) turns out to be more active than the zeolite, the chemoselectivity is elusive: compounds 2a,b undergo simultaneous S-methylation and esterification reactions, and acids 3-5 yield complex mixtures of products of O-methylation, O-methoxycarbonylation, and esterification of their OH and CO2H groups, respectively. Overall, the combined use of a nontoxic reagent/solvent (DMC) and a safe promoter (NaY) imparts a genuine ecofriendly nature to the investigated synthesis.

  1. Design of an effective bifunctional catalyst organotriphosphonic acid-functionalized ferric alginate (ATMP-FA) and optimization by Box-Behnken model for biodiesel esterification synthesis of oleic acid over ATMP-FA.

    PubMed

    Liu, Wei; Yin, Ping; Liu, Xiguang; Qu, Rongjun

    2014-12-01

    Biodiesel production has become an intense research area because of rapidly depleting energy reserves and increasing petroleum prices together with environmental concerns. This paper focused on the optimization of the catalytic performance in the esterification reaction of oleic acid for biodiesel production over the bifunctional catalyst organotriphosphonic acid-functionalized ferric alginate ATMP-FA. The reaction parameters including catalyst amount, ethanol to oleic acid molar ratio and reaction temperature have been optimized by response surface methodology (RSM) using the Box-Behnken model. It was found that the reaction temperature was the most significant factor, and the best conversion ratio of oleic acid could reach 93.17% under the reaction conditions with 9.53% of catalyst amount and 8.62:1 of ethanol to oleic acid molar ratio at 91.0 °C. The research results show that two catalytic species could work cooperatively to promote the esterification reaction, and the bifunctional ATMP-FA is a potential catalyst for biodiesel production.

  2. The effects of sterol structure upon sterol esterification.

    PubMed

    Lin, Don S; Steiner, Robert D; Merkens, Louise S; Pappu, Anuradha S; Connor, William E

    2010-01-01

    Cholesterol is esterified in mammals by two enzymes: LCAT (lecithin cholesterol acyltransferase) in plasma and ACAT(1) and ACAT(2) (acyl-CoA cholesterol acyltransferases) in the tissues. We hypothesized that the sterol structure may have significant effects on the outcome of esterification by these enzymes. To test this hypothesis, we analyzed sterol esters in plasma and tissues in patients having non-cholesterol sterols (sitosterolemia and Smith-Lemli-Opitz syndrome). The esterification of a given sterol was defined as the sterol ester percentage of total sterols. The esterification of cholesterol in plasma by LCAT was 67% and in tissues by ACAT was 64%. Esterification of nine sterols (cholesterol, cholestanol, campesterol, stigmasterol, sitosterol, campestanol, sitostanol, 7-dehydrocholesterol and 8-dehydrocholesterol) was examined. The relative esterification (cholesterol being 1.0) of these sterols by the plasma LCAT was 1.00, 0.95, 0.89, 0.40, 0.85, 0.82 and 0.80, 0.69 and 0.82, respectively. The esterification by the tissue ACAT was 1.00, 1.29, 0.75, 0.49, 0.45, 1.21 and 0.74, respectively. The predominant fatty acid of the sterol esters was linoleic acid for LCAT and oleic acid for ACAT. We compared the esterification of two sterols differing by only one functional group (a chemical group attached to sterol nucleus) and were able to quantify the effects of individual functional groups on sterol esterification. The saturation of the A ring of cholesterol increased ester formation by ACAT by 29% and decreased the esterification by LCAT by 5.9%. Esterification by ACAT and LCAT was reduced, respectively, by 25 and 11% by the presence of an additional methyl group on the side chain of cholesterol at the C-24 position. This data supports our hypothesis that the structure of the sterol substrate has a significant effect on its esterification by ACAT or LCAT.

  3. High-throughput profiling of protein N-glycosylation by MALDI-TOF-MS employing linkage-specific sialic acid esterification.

    PubMed

    Reiding, Karli R; Blank, Dennis; Kuijper, Dennis M; Deelder, André M; Wuhrer, Manfred

    2014-06-17

    Protein glycosylation is an important post-translational modification associated, among others, with diseases and the efficacy of biopharmaceuticals. Matrix-assisted laser desorption/ionization (MALDI) time-of-fight (TOF) mass spectrometry (MS) can be performed to study glycosylation in a high-throughput manner, but is hampered by the instability and ionization bias experienced by sialylated glycan species. Stabilization and neutralization of these sialic acids can be achieved by permethylation or by specific carboxyl group derivatization with the possibility of discrimination between α2,3- and α2,6-linked sialic acids. However, these methods typically require relatively pure glycan samples, show sensitivity to side reactions, and need harsh conditions or long reaction times. We established a rapid, robust and linkage-specific high-throughput method for sialic acid stabilization and MALDI-TOF-MS analysis, to allow direct modification of impure glycan-containing mixtures such as PNGase F-released human plasma N-glycome. Using a combination of carboxylic acid activators in ethanol achieved near-complete ethyl esterification of α2,6-linked sialic acids and lactonization of α2,3-linked variants, in short time using mild conditions. Glycans were recovered by hydrophilic interaction liquid chromatography solid phase extraction and analyzed by MALDI-TOF-MS in reflectron positive mode with 2,5-dihydroxybenzoic acid as the matrix substance. Analysis of the human plasma N-glycome allowed high-throughput detection and relative quantitation of more than 100 distinct N-glycan compositions with varying sialic acid linkages. PMID:24831253

  4. An Oral Load of [13C3]Glycerol and Blood NMR Analysis Detect Fatty Acid Esterification, Pentose Phosphate Pathway, and Glycerol Metabolism through the Tricarboxylic Acid Cycle in Human Liver.

    PubMed

    Jin, Eunsook S; Sherry, A Dean; Malloy, Craig R

    2016-09-01

    Drugs and other interventions for high impact hepatic diseases often target biochemical pathways such as gluconeogenesis, lipogenesis, or the metabolic response to oxidative stress. However, traditional liver function tests do not provide quantitative data about these pathways. In this study, we developed a simple method to evaluate these processes by NMR analysis of plasma metabolites. Healthy subjects ingested [U-(13)C3]glycerol, and blood was drawn at multiple times. Each subject completed three visits under differing nutritional states. High resolution (13)C NMR spectra of plasma triacylglycerols and glucose provided new insights into a number of hepatic processes including fatty acid esterification, the pentose phosphate pathway, and gluconeogenesis through the tricarboxylic acid cycle. Fasting stimulated pentose phosphate pathway activity and metabolism of [U-(13)C3]glycerol in the tricarboxylic acid cycle prior to gluconeogenesis or glyceroneogenesis. Fatty acid esterification was transient in the fasted state but continuous under fed conditions. We conclude that a simple NMR analysis of blood metabolites provides an important biomarker of pentose phosphate pathway activity, triacylglycerol synthesis, and flux through anaplerotic pathways in mitochondria of human liver.

  5. An Oral Load of [13C3]Glycerol and Blood NMR Analysis Detect Fatty Acid Esterification, Pentose Phosphate Pathway, and Glycerol Metabolism through the Tricarboxylic Acid Cycle in Human Liver.

    PubMed

    Jin, Eunsook S; Sherry, A Dean; Malloy, Craig R

    2016-09-01

    Drugs and other interventions for high impact hepatic diseases often target biochemical pathways such as gluconeogenesis, lipogenesis, or the metabolic response to oxidative stress. However, traditional liver function tests do not provide quantitative data about these pathways. In this study, we developed a simple method to evaluate these processes by NMR analysis of plasma metabolites. Healthy subjects ingested [U-(13)C3]glycerol, and blood was drawn at multiple times. Each subject completed three visits under differing nutritional states. High resolution (13)C NMR spectra of plasma triacylglycerols and glucose provided new insights into a number of hepatic processes including fatty acid esterification, the pentose phosphate pathway, and gluconeogenesis through the tricarboxylic acid cycle. Fasting stimulated pentose phosphate pathway activity and metabolism of [U-(13)C3]glycerol in the tricarboxylic acid cycle prior to gluconeogenesis or glyceroneogenesis. Fatty acid esterification was transient in the fasted state but continuous under fed conditions. We conclude that a simple NMR analysis of blood metabolites provides an important biomarker of pentose phosphate pathway activity, triacylglycerol synthesis, and flux through anaplerotic pathways in mitochondria of human liver. PMID:27432878

  6. Synthesis of sulfated titania supported on mesoporous silica using direct impregnation and its application in esterification of acetic acid and n-butanol

    SciTech Connect

    Wang Yuhong; Gan Yunting; Whiting, Roger; Lu Guanzhong

    2009-09-15

    A new method has been developed for the preparation of sulfated titania (S-TiO{sub 2}) supported on mesoporous silica. The use of direct exchange of metal containing precursors for the surfactants in the as-synthesized MCM-41 substrate produced a product with high sulfur content without serious blockage of the pore structure of MCM-41. The pore sizes and volumes of the resultant S-TiO{sub 2}/MCM-41 composites were found to vary markedly with the loading of TiO{sub 2}. The strong acidic character of the composites obtained was examined by using them as catalysts for the esterification of acetic acid and n-butanol. - Abstract: XRD profiles of the composites of S-TiO{sub 2}/MCM-41 with different TiO{sub 2} contents. The low angle peaks indicate the MCM-41-like structure retained and a TiO{sub 2} phase appeared at high angle region. Display Omitted

  7. Functional characterization of a novel aspartic acid rich lipase, TALipC, from Trichosporon asahii MSR54: solvent-dependent enantio inversion during esterification of 1-phenylethanol.

    PubMed

    Kumari, Arti; Gupta, Rani

    2015-01-01

    A novel lipase gene TAlipC was isolated from Trichosporon asahii MSR54 and functionally expressed in Pichia pastoris. The protein was His-tagged and purified to homogeneity by affinity chromatography. Sequence comparison revealed a high homology with lipases from Cryptococcus sp. It had a GX type oxyanion hole and a GHSLG-type conserved penta-peptide similar to those in the lipases from Yarrowia lipolytica. The enzyme had optimal activity at pH 8 and 50 °C. It was specific for long chain fatty acid groups of p-nitrophenol esters and triacylglycerols, showing regio- and enantio-selectivity. It was activated by Mg(2+) ions (20 mM) and had a predicted Mg-binding domain at the aspartic acid-rich C-terminal. Solvent-based enantio- inversion was the key feature of the enzyme where it showed (S)-selectivity in 1,4-dioxane and 2-propanol and (R)-selectivity in hexane during chiral separation of (±)1-phenylethanol by esterification.

  8. Selective and recyclable depolymerization of cellulose to levulinic acid catalyzed by acidic ionic liquid.

    PubMed

    Ren, Huifang; Girisuta, Buana; Zhou, Yonggui; Liu, Li

    2015-03-01

    Cellulose depolymerization to levulinic acid (LA) was catalyzed by acidic ionic liquids (ILs) selectively and recyclably under hydrothermal conditions. The effects of reaction temperature, time, water amount and cellulose intake were investigated. Dilution effect becomes more pronounced at lower cellulose intake, dramatically improving the yield of LA to 86.1%. A kinetic model has been developed based on experimental data, whereby a good fit was obtained and kinetic parameters were derived. The relationships between IL structure, polymeric structure and depolymerization efficiency were established, shedding light on the in-depth catalytic mechanism of IL, inclusive of acidity and hydrogen bonding ability. The LA product can be readily separated through extraction by methyl isobutyl ketone (MIBK) and IL can be reused over five cycles without loss of activity. This environmentally friendly methodology can be applied to selective production of LA from versatile biomass feedstocks, including cellulose and derivatives, glucose, fructose and HMF.

  9. Chemoselective Conversion from α-Hydroxy Acids to α-Keto Acids Enabled by Nitroxyl-Radical-Catalyzed Aerobic Oxidation.

    PubMed

    Furukawa, Keisuke; Inada, Haruki; Shibuya, Masatoshi; Yamamoto, Yoshihiko

    2016-09-01

    The chemoselective oxidation of α-hydroxy acids to α-keto acids catalyzed by 2-azaadamantane N-oxyl (AZADO), a nitroxyl radical catalyst, is described. Although α-keto acids are labile and can easily release CO2 under oxidation conditions, the use of molecular oxygen as a cooxidant enables the desired chemoselective oxidation. PMID:27533283

  10. A highly enantioselective amino acid-catalyzed route to functionalized alpha-amino acids.

    PubMed

    Córdova, Armando; Notz, Wolfgang; Zhong, Guofu; Betancort, Juan M; Barbas, Carlos F

    2002-03-01

    The development of syntheses providing enantiomerically pure alpha-amino acids has intrigued generations of chemists and been the subject of intense research. This report describes a general approach to functionalized alpha-amino acids based on catalytic asymmetric synthesis. Proline catalyzed Mannich-type reactions of N-PMP-protected alpha-imino ethyl glyoxylate with a variety of unmodified ketones to provide functionalized alpha-amino acids in high yields with excellent regio-, diastereo-, and enantioselectivities. Study of seven examples yielded six with product ee values of > or = 99%. In reactions involving ketone donors where diastereoisomeric products could be formed, two adjacent stereogenic centers were created simultaneously upon carbon-carbon bond formation with complete syn-stereocontrol. Significantly, this methodology utilizes readily available and rather inexpensive starting materials, does not require any preactivation of substrates or metal ion assistance, and can be carried out on a gram scale under operationally simple reaction conditions. The keto-functionality present in the products provides a particularly attractive site for versatile modifications. This study compliments and extends our bioorganic approach to asymmetric synthesis to a versatile synthon class. Given that we have shown that a variety of optically active amino acids can be synthesized with proline catalysis, where an L-amino acid begets other L-amino acids, our results may stimulate thoughts concerning prebiotic syntheses of optically active amino acids based on this route.

  11. Lipase catalyzed synthesis of neutral glycerides rich in micronutrients from rice bran oil fatty acid distillate.

    PubMed

    Nandi, Sumit; Gangopadhyay, Sarbani; Ghosh, Santinath

    2008-01-01

    Neutral glycerides with micronutrients like sterols, tocopherols and squalene may be prepared from cheap raw material like rice bran oil fatty acid distillate (RBO FAD). RBO FAD is an important byproduct of vegetable oil refining industries in the physical refining process. Glycerides like triacylglycerols (TAG), diacylglycerols (DAG) and monoacylglycerols (MAG) containing significant amounts of unsaponifiable matter like sterols, tocopherols and hydrocarbons (mainly squalene) may certainly be considered as novel functional food ingredients. Fatty acids present in RBO FAD were esterified with glycerol of varying amount (1:0.33, 1:0.5, 1:1 and 1:1.5 of FAD : glycerol ratio) for 8 h using non-specific enzyme NS 40013 (Candida antartica). After esterification the product mixture containing mono, di- and triglycerides was purified by molecular distillation to remove excess free fatty acids and also other volatile undesirable components. The purified product containing sterols, tocopherols and squalene can be utilized in various food formulations. PMID:18838832

  12. Lipase catalyzed synthesis of neutral glycerides rich in micronutrients from rice bran oil fatty acid distillate.

    PubMed

    Nandi, Sumit; Gangopadhyay, Sarbani; Ghosh, Santinath

    2008-01-01

    Neutral glycerides with micronutrients like sterols, tocopherols and squalene may be prepared from cheap raw material like rice bran oil fatty acid distillate (RBO FAD). RBO FAD is an important byproduct of vegetable oil refining industries in the physical refining process. Glycerides like triacylglycerols (TAG), diacylglycerols (DAG) and monoacylglycerols (MAG) containing significant amounts of unsaponifiable matter like sterols, tocopherols and hydrocarbons (mainly squalene) may certainly be considered as novel functional food ingredients. Fatty acids present in RBO FAD were esterified with glycerol of varying amount (1:0.33, 1:0.5, 1:1 and 1:1.5 of FAD : glycerol ratio) for 8 h using non-specific enzyme NS 40013 (Candida antartica). After esterification the product mixture containing mono, di- and triglycerides was purified by molecular distillation to remove excess free fatty acids and also other volatile undesirable components. The purified product containing sterols, tocopherols and squalene can be utilized in various food formulations.

  13. Quantitative Structure-Property Relationship (QSPR) Models for a Local Quantum Descriptor: Investigation of the 4- and 3-Substituted-Cinnamic Acid Esterification.

    PubMed

    Rodrigues-Santos, Cláudio E; Echevarria, Aurea; Sant'Anna, Carlos M R; Bitencourt, Thiago B; Nascimento, Maria G; Bauerfeldt, Glauco F

    2015-09-22

    In this work, the theoretical description of the 4- and 3-substituted-cinnamic acid esterification with different electron donating and electron withdrawing groups was performed at the B3LYP and M06-2X levels, as a two-step process: the O-protonation and the nucleophile attack by ethanol. In parallel, an experimental work devoted to the synthesis and characterization of the substituted-cinnamate esters has also been performed. In order to quantify the substituents effects, quantitative structure-property relationship (QSPR) models based on the atomic charges, Fukui functions and the Frontier Effective-for-Reaction Molecular Orbitals (FERMO) energies were investigated. In fact, the Fukui functions, ƒ⁺C and ƒ(-)O, indicated poor correlations for each individual step, and in contrast with the general literature, the O-protonation step is affected both by the FERMO energies and the O-charges of the carbonyl group. Since the process was shown to not be totally described by either charge- or frontier-orbitals, it is proposed to be frontier-charge-miscere controlled. Moreover, the observed trend for the experimental reaction yields suggests that the electron withdrawing groups favor the reaction and the same was observed for Step 2, which can thus be pointed out as the determining step.

  14. Benzoic acid 2-hydroxylase, a soluble oxygenase from tobacco, catalyzes salicylic acid biosynthesis

    SciTech Connect

    Leon, J.; Shulaev, V.; Yalpani, N.

    1995-10-24

    Benzoic acid 2-hydroxylase (BA2H) catalyzes the biosynthesis of salicylic acid from benzoic acid. The enzyme has been partially purified and characterized as a soluble protein of 160 kDa. High-efficiency in vivo labeling of salicyclic acid with {sup 18}O{sub 2} suggested that BA2H is an oxygenase that specifically hydroxylates the ortho position of benzoic acid. The enzyme was strongly induced by either tobacco mosaic virus inoculation of benzoic acid infiltration of tobacco leaves and it was inhibited by CO and other inhibitors of cytochrome P450 hydroxylases. The BA2H activity was immunodepleted by antibodies raised against SU2, a soluble cytochrome P450 from Streptomyces griseolus. The anti-SU2 antibodies immunoprecipitated a radiolabeled polypeptide of around 160 kDa from the soluble protein extracts of L-[{sup 35}S]-methionine-fed tobacco leaves. Purified BA2H showed CO-difference spectra with a maximum at 457 nm. These data suggest that BA2H belongs to a novel class of soluble, high molecular weight cytochrome P450 enzymes. 21 refs., 6 figs., 1 tab.

  15. KI-catalyzed α-acyloxylation of acetone with carboxylic acids.

    PubMed

    Wu, Ya-Dong; Huang, Bei; Zhang, Yue-Xin; Wang, Xiao-Xu; Dai, Jian-Jun; Xu, Jun; Xu, Hua-Jian

    2016-07-01

    The KI-catalyzed reaction of acetone with aromatic carboxylic acids is achieved, leading to α-acyloxycarbonyl compounds in good to excellent yields under mild reaction conditions. The present method exhibits good functional-group compatibility. Notably, this reaction system is even suitable for cinnamic acid, 3-phenylpropiolic acid and 4-phenylbutanoic acid. A kinetic isotope effect (KIE) study indicates that C-H cleavage of the acetone is the rate-limiting step in the catalytic cycle. PMID:27251323

  16. Formation of Linear Polyenes in Thermal Dehydration of Polyvinyl Alcohol, Catalyzed by Phosphotungstic Acid

    NASA Astrophysics Data System (ADS)

    Tretinnikov, O. N.; Sushko, N. I.

    2015-01-01

    In order to obtain linear polyenes in polyvinyl alcohol films via acid-catalyzed thermal dehydration of the polyvinyl alcohol, we used phosphotungstic acid as the catalyst: a safe and heat-stable solid chemical compound. We established that phosphotungstic acid, introduced as solid nanoparticles into polyvinyl alcohol films, is a more effective dehydration catalyst than hydrochloric acid, since in contrast to HCl it does not evaporate from the film during heat treatment.

  17. Mechanism of Boron-Catalyzed N-Alkylation of Amines with Carboxylic Acids.

    PubMed

    Zhang, Qi; Fu, Ming-Chen; Yu, Hai-Zhu; Fu, Yao

    2016-08-01

    Mechanistic study has been carried out on the B(C6F5)3-catalyzed amine alkylation with carboxylic acid. The reaction includes acid-amine condensation and amide reduction steps. In condensation step, the catalyst-free mechanism is found to be more favorable than the B(C6F5)3-catalyzed mechanism, because the automatic formation of the stable B(C6F5)3-amine complex deactivates the catalyst in the latter case. Meanwhile, the catalyst-free condensation is constituted by nucleophilic attack and the indirect H2O-elimination (with acid acting as proton shuttle) steps. After that, the amide reduction undergoes a Lewis acid (B(C6F5)3)-catalyzed mechanism rather than a Brønsted acid (B(C6F5)3-coordinated HCOOH)-catalyzed one. The B(C6F5)3)-catalyzed reduction includes twice silyl-hydride transfer steps, while the first silyl transfer is the rate-determining step of the overall alkylation catalytic cycle. The above condensation-reduction mechanism is supported by control experiments (on both temperature and substrates). Meanwhile, the predicted chemoselectivity is consistent with the predominant formation of the alkylation product (over disilyl acetal product). PMID:27441997

  18. The Lewis-acid-catalyzed synthesis of hyperbranched poly(glycerol-diacid)s in toluene

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The first examples of monomeric glycerol-derived hyperbranched polyesters produced in a non-polar solvent system are reported here. The polymers were made by the Lewis acid (dibutyltin(IV)oxide)-catalyzed polycondensation of glycerol with either succinic acid (n (aliphatic chain length)=2), glutari...

  19. Lipase-catalyzed synthesis of monoacylglycerol in a homogeneous system.

    PubMed

    Monteiro, Julieta B; Nascimento, Maria G; Ninow, Jorge L

    2003-04-01

    The 1,3-regiospecifique lipase, Lipozyme IM, catalyzed the esterification of lauric acid and glycerol in a homogeneous system. To overcome the drawback of the insolubility of glycerol in hexane, which is extensively used in enzymatic synthesis, a mixture of n-hexane/tert-butanol (1:1, v/v) was used leading to a monophasic system. The conversion of lauric acid into monolaurin was 65% in 8 h, when a molar ratio of glycerol to fatty acid (5:1) was used with the fatty acid at 0.1 M, and the phenomenon of acyl migration was minimized.

  20. Scandium trifluoromethanesulfonate as an extremely active Lewis acid catalyst in acylation of alcohols with acid anhydrides and mixed anhydrides

    SciTech Connect

    Ishihara, K.; Kubota, M.; Kurihara, H.; Yamamoto, H.

    1996-07-12

    Scandium triflate catalyzes the acylation of alcohols with acid anhydrides or the esterification of alcohols by carboxylic acids in the presence of p-nitrobenzoic anhydrides. The catalytic activity of the scandium triflates is found to be quite high allowing the acylation of secondary and tertiary alcohols.

  1. Acid-catalyzed heterogeneous reaction of 3-methyl-2-buten-1-ol with hydrogen peroxide.

    PubMed

    Liu, Qifan; Wang, Weigang; Ge, Maofa

    2015-05-01

    Acid-catalyzed heterogeneous oxidation with hydrogen peroxide (H2O2) has been suggested to be a potential pathway for secondary organic aerosol (SOA) formation from isoprene and its oxidation products. However, knowledge of the chemical mechanism and kinetics for this process is still incomplete. 3-Methyl-2-buten-1-ol (MBO321), an aliphatic alcohol structurally similar to isoprene, is emitted by pine forests and widely used in the manufacturing industries. Herein the uptake of MBO321 into H2SO4-H2O2 mixed solution was investigated using a flow-tube reactor coupled to a mass spectrometer. The reactive uptake coefficients (γ) were acquired for the first time and were found to increase rapidly with increasing acid concentration. Corresponding aqueous-phase reactions were performed to further study the mechanism of this acid-catalyzed reaction. MBO321 could convert to 2-methyl-3-buten-2-ol (MBO232) and yield isoprene in acidic media. Organic hydroperoxides (ROOHs) were found to be generated through the acid-catalyzed route, which could undergo a rearrangement reaction and result in the formation of acetone and acetaldehyde. Organosulfates, which have been proposed to be SOA tracer compounds in the atmosphere, were also produced during the oxidation process. These results suggest that the heterogeneous acid-catalyzed reaction of MBO321 with H2O2 may contribute to SOA mass under certain atmospheric conditions.

  2. Direct Ruthenium-Catalyzed Hydrogenation of Carboxylic Acids to Alcohols.

    PubMed

    Cui, Xinjiang; Li, Yuehui; Topf, Christoph; Junge, Kathrin; Beller, Matthias

    2015-09-01

    The "green" reduction of carboxylic acids to alcohols is a challenging task in organic chemistry. Herein, we describe a general protocol for generation of alcohols by catalytic hydrogenation of carboxylic acids. Key to success is the use of a combination of Ru(acac)3, triphos and Lewis acids. The novel method showed broad substrate tolerance and a variety of aliphatic carboxylic acids including biomass-derived compounds can be smoothly reduced.

  3. Acid-catalyzed autohydrolysis of wheat straw to improve sugar recovery.

    PubMed

    Ertas, Murat; Han, Qiang; Jameel, Hasan

    2014-10-01

    A comparison study of autohydrolysis and acid-catalyzed autohydrolysis of wheat straw was performed to understand the impact of acid addition on overall sugar recovery. Autohydrolysis combined with refining is capable of achieving sugar recoveries in the mid 70s. If the addition of a small amount of acid is capable of increasing the sugar recovery even higher it may be economically attractive. Acetic, sulfuric, hydrochloric and sulfurous acids were selected for acid-catalyzed autohydrolysis pretreatments. Autohydrolysis with no acid at 190 °C showed the highest total sugar in the prehydrolyzate. Enzymatic hydrolysis was performed for all the post-treated solids with and without refining at enzyme loadings of 4 and 10 FPU/g for 96 h. Acid-catalyzed autohydrolysis at 190 °C with sulfurous acid showed the highest total sugar recovery of 81.2% at 4 FPU/g enzyme charge compared with 64.3% at 190 °C autohydrolysis without acid.

  4. Ethyl Esterification for MALDI-MS Analysis of Protein Glycosylation.

    PubMed

    Reiding, Karli R; Lonardi, Emanuela; Hipgrave Ederveen, Agnes L; Wuhrer, Manfred

    2016-01-01

    Ethyl esterification is a technique for the chemical modification of sialylated glycans, leading to enhanced stability when performing matrix-assisted laser desorption/ionization (MALDI)-mass spectrometry (MS), as well as allowing the efficient detection of both sialylated and non-sialylated glycans in positive ion mode. In addition, the method shows specific reaction products for α2,3- and α2,6-linked sialic acids, leading to an MS distinguishable mass difference. Here, we describe the ethyl esterification protocol for 96 glycan samples, including enzymatic N-glycan release, the aforementioned ethyl esterification, glycan enrichment, MALDI target preparation, and the MS(/MS) measurement. PMID:26700047

  5. Dietary phenolic acids and ascorbic acid: Influence on acid-catalyzed nitrosative chemistry in the presence and absence of lipids.

    PubMed

    Combet, Emilie; El Mesmari, Aziza; Preston, Tom; Crozier, Alan; McColl, Kenneth E L

    2010-03-15

    Acid-catalyzed nitrosation and production of potentially carcinogenic nitrosative species is focused at the gastroesophageal junction, where salivary nitrite, derived from dietary nitrate, encounters the gastric juice. Ascorbic acid provides protection by converting nitrosative species to nitric oxide (NO). However, NO may diffuse into adjacent lipid, where it reacts with O(2) to re-form nitrosative species and N-nitrosocompounds (NOC). In this way, ascorbic acid promotes acid nitrosation. Using a novel benchtop model representing the gastroesophageal junction, this study aimed to clarify the action of a range of water-soluble antioxidants on the nitrosative mechanisms in the presence or absence of lipids. Caffeic, ferulic, gallic, or chlorogenic and ascorbic acids were added individually to simulated gastric juice containing secondary amines, with or without lipid. NO and O(2) levels were monitored by electrochemical detection. NOC were measured in both aqueous and lipid phases by gas chromatography-tandem mass spectrometry. In the absence of lipids, all antioxidants tested inhibited nitrosation, ranging from 35.9 + or - 7.4% with gallic acid to 93 + or - 0.6% with ferulic acid. In the presence of lipids, the impact of each antioxidant on nitrosation was inversely correlated with the levels of NO they generated (R(2) = 0.95, p<0.01): gallic, chlorogenic, and ascorbic acid promoted nitrosation, whereas ferulic and caffeic acids markedly inhibited nitrosation.

  6. Esterification Catalysis by Pyridinium p-Toluenesulfonate Revisited—Modification with a Lipid Chain for Improved Activities and Selectivities

    PubMed Central

    Wang, Wei; Liu, Huimin; Xu, Shaoyi; Gao, Yong

    2013-01-01

    The lipid analogues of pyridinium p-toluenesulfonate (PPTS) were examined for catalyzing the condensation of an equimolar mixture of carboxylic acids and alcohols under mild conditions without removal of water. Although PPTS is a poor catalyst, the introduction of a lipid chain and nitro group significantly improved the activity of PPTS and led to selectivity at suppressing elimination side reactions of alcohols. 2-Oleamido-5-nitro-pyridinium p-toluenesulfonate (6) is a lead catalyst that promoted various esterification reactions with yields up to 99%. PMID:24039303

  7. Silver-catalyzed arylation of (hetero)arenes by oxidative decarboxylation of aromatic carboxylic acids.

    PubMed

    Kan, Jian; Huang, Shijun; Lin, Jin; Zhang, Min; Su, Weiping

    2015-02-01

    A long-standing challenge in Minisci reactions is achieving the arylation of heteroarenes by oxidative decarboxylation of aromatic carboxylic acids. To address this challenge, the silver-catalyzed intermolecular Minisci reaction of aromatic carboxylic acids was developed. With an inexpensive silver salt as a catalyst, this new reaction enables a variety of aromatic carboxylic acids to undergo decarboxylative coupling with electron-deficient arenes or heteroarenes regardless of the position of the substituents on the aromatic carboxylic acid, thus eliminating the need for ortho-substituted aromatic carboxylic acids, which were a limitation of previously reported methods.

  8. Iridium-catalyzed enantioselective hydrogenation of unsaturated heterocyclic acids.

    PubMed

    Song, Song; Zhu, Shou-Fei; Pu, Liu-Yang; Zhou, Qi-Lin

    2013-06-01

    Spiral binding: A highly enantioselective hydrogenation of unsaturated heterocyclic acids has been developed by using chiral iridium/spirophosphino oxazoline catalysts (see scheme; BArF(-) =tetrakis[3,5-bis(trifluoromethyl)phenyl]borate, Boc=tert-butoxycarbonyl). This reaction provided an efficient method for the preparation of optically active heterocyclic acids with excellent enantioselectivities. PMID:23610004

  9. Solvent-free lipase-catalyzed synthesis of a novel hydroxyl-fatty acid derivative of kojic acid.

    PubMed

    El-Boulifi, Noureddin; Ashari, Siti Efliza; Serrano, Marta; Aracil, Jose; Martínez, Mercedes

    2014-02-01

    The aim of this work was the synthesis of a novel hydroxyl-fatty acid derivative of kojic acid rich in kojic acid monoricinoleate (KMR) which can be widely used in the cosmetic and food industry. The synthesis of KMR was carried out by lipase-catalysed esterification of ricinoleic and kojic acids in solvent-free system. Three immobilized lipases were tested and the best KMR yields were attained with Lipozyme TL IM and Novozym 435. Since Lipozyme TL IM is the cheapest, it was selected to optimize the reaction conditions. The optimal reaction conditions were 80 °C for the temperature, 1:1 for the alcohol/acid molar ratio, 600 rpm for stirring speed and 7.8% for the catalyst concentration. Under these conditions, the reaction was scaled up in a 5×10⁻³ m³ stirred tank reactor. ¹H-¹³C HMBC-NMR showed that the primary hydroxyl group of kojic acid was regioselectively esterified. The KMR has more lipophilicity than kojic acid and showed antioxidant activity that improves the oxidation stability of biodiesel.

  10. Rh-catalyzed sulfonic acid group directed ortho C-H olefination of arenes.

    PubMed

    Dong, Yi; Liu, Gang

    2013-09-21

    A Rh-catalyzed ortho C-H olefination of arenes directed by a sulfonic acid group was developed with good yields and a broad reaction scope. Efficient performance of the catalyst caused this electron-poor aromatic C-H to be activated effectively and unactivated alkenes are also suitable for this reaction.

  11. Copper-catalyzed C-N cross-coupling of sulfondiimines with boronic acids.

    PubMed

    Bohmann, Rebekka Anna; Bolm, Carsten

    2013-09-01

    The copper-catalyzed C-N cross-coupling of sulfondiimines with boronic acids has been developed. The reaction proceeds at room temperature in good to excellent yields and provides access to a variety of N,N'-disubstituted sulfondiimines, including N-(hetero)aryl sulfondiimines and the first reported N-alkenylated sulfondiimine. PMID:23937076

  12. Brønsted acid-catalyzed Nazarov cyclization of pyrrole derivatives accelerated by microwave irradiation.

    PubMed

    Bachu, Prabhakar; Akiyama, Takahiko

    2009-07-15

    The Brønsted acid-catalyzed Nazarov cyclization of pyrrole derivatives was developed. Microwave irradiation accelerated the Nazarov cyclization significantly at 40 degrees C to give cyclopenta[b]pyrrole derivatives in excellent yields with high trans selectivity. PMID:19447615

  13. Transformation of cellulose and its derived carbohydrates into formic and lactic acids catalyzed by vanadyl cations.

    PubMed

    Tang, Zhenchen; Deng, Weiping; Wang, Yanliang; Zhu, Enze; Wan, Xiaoyue; Zhang, Qinghong; Wang, Ye

    2014-06-01

    The transformation of cellulose or cellulose-derived carbohydrates into platform chemicals is the key to establish biomass-based sustainable chemical processes. The systems able to catalyze the conversion of cellulose into key chemicals in water without the consumption of hydrogen are limited. We report that simple vanadyl (VO(2+)) cations catalyze the conversions of cellulose and its monomer, glucose, into lactic acid and formic acid in water. We have discovered an interesting shift of the major product from formic acid to lactic acid on switching the reaction atmosphere from oxygen to nitrogen. Our studies suggest that VO(2+) catalyzes the isomerization of glucose to fructose, the retro-aldol fragmentation of fructose to two trioses, and the isomerization of trioses, which leads to the formation of lactic acid under anaerobic conditions. The oxidative cleavage of C-C bonds in the intermediates caused by the redox conversion of VO2(+)/VO(2+) under aerobic conditions results in formic acid and CO2. We demonstrate that the addition of an alcohol suppresses the formation of CO2 and enhances the formic acid yield significantly to 70-75 %.

  14. Transformation of cellulose and its derived carbohydrates into formic and lactic acids catalyzed by vanadyl cations.

    PubMed

    Tang, Zhenchen; Deng, Weiping; Wang, Yanliang; Zhu, Enze; Wan, Xiaoyue; Zhang, Qinghong; Wang, Ye

    2014-06-01

    The transformation of cellulose or cellulose-derived carbohydrates into platform chemicals is the key to establish biomass-based sustainable chemical processes. The systems able to catalyze the conversion of cellulose into key chemicals in water without the consumption of hydrogen are limited. We report that simple vanadyl (VO(2+)) cations catalyze the conversions of cellulose and its monomer, glucose, into lactic acid and formic acid in water. We have discovered an interesting shift of the major product from formic acid to lactic acid on switching the reaction atmosphere from oxygen to nitrogen. Our studies suggest that VO(2+) catalyzes the isomerization of glucose to fructose, the retro-aldol fragmentation of fructose to two trioses, and the isomerization of trioses, which leads to the formation of lactic acid under anaerobic conditions. The oxidative cleavage of C-C bonds in the intermediates caused by the redox conversion of VO2(+)/VO(2+) under aerobic conditions results in formic acid and CO2. We demonstrate that the addition of an alcohol suppresses the formation of CO2 and enhances the formic acid yield significantly to 70-75 %. PMID:24798653

  15. Rh(III)-catalyzed synthesis of sultones through C-H activation directed by a sulfonic acid group.

    PubMed

    Qi, Zisong; Wang, Mei; Li, Xingwei

    2014-09-01

    A new rhodium-catalyzed synthesis of sultones via the oxidative coupling of sulfonic acids with internal alkynes is described. The reaction proceeds via aryl C-H activation assisted by a sulfonic acid group.

  16. Chemoselective nucleophilic arylation and single-step oxidative esterification of aldehydes using siloxanes and a palladium-phosphinous acid as a reaction switch.

    PubMed

    Lerebours, Rachel; Wolf, Christian

    2006-10-11

    Aldehydes and siloxanes form methyl esters in a single step through mild oxidative esterification in the presence of a palladium catalyst or, alternatively, afford secondary alcohols via TBAF-promoted arylation in the absence of a catalyst at increased temperatures under otherwise identical reaction conditions.

  17. Anti-melanogenic effects of resveratryl triglycolate, a novel hybrid compound derived by esterification of resveratrol with glycolic acid.

    PubMed

    Park, Soojin; Seok, Jin Kyung; Kwak, Jun Yup; Choi, Yun-Hyeok; Hong, Seong Su; Suh, Hwa-Jin; Park, Woncheol; Boo, Yong Chool

    2016-07-01

    Resveratrol is known to inhibit cellular melanin synthesis by multiple mechanisms. Glycolic acid (GA) is used in skin care products for its excellent skin penetration. The purpose of this study was to examine the anti-melanogenic effects of resveratryl triglycolate (RTG), a novel hybrid compound of resveratrol and GA, in comparison with resveratrol, GA, resveratryl triacetate (RTA) and arbutin. Resveratrol, RTG, and RTA inhibited the catalytic activity human tyrosinase (TYR) more potently than arbutin or GA did. Their cytotoxic and anti-melanogenic effects were examined using murine melanoma B16/F10 cells and human epidermal melanocytes (HEMs). The cytotoxicity of RTG was similar to that of resveratrol and RTA. RTG at 3-10 μM decreased melanin levels and cellular TYR activities in α-melanocyte-stimulating hormone-stimulated B16/F10 cells, and L-tyrosine-stimulated HEMs. RTG also suppressed mRNA and protein expression of TYR, tyrosinase-related protein 1, L-3,4-dihydroxyphenylalanine chrome tautomerase, and microphthalmia-associated transcription factor (MITF) in HEMs stimulated with L-tyrosine. This study suggests that, like resveratrol and RTA, RTG can attenuate cellular melanin synthesis effectively through the suppression of MITF-dependent expression of melanogenic enzymes and the inhibition of catalytic activity of TYR enzyme. RTG therefore has potential for use as a cosmeceutical ingredient for skin whitening.

  18. Anti-melanogenic effects of resveratryl triglycolate, a novel hybrid compound derived by esterification of resveratrol with glycolic acid.

    PubMed

    Park, Soojin; Seok, Jin Kyung; Kwak, Jun Yup; Choi, Yun-Hyeok; Hong, Seong Su; Suh, Hwa-Jin; Park, Woncheol; Boo, Yong Chool

    2016-07-01

    Resveratrol is known to inhibit cellular melanin synthesis by multiple mechanisms. Glycolic acid (GA) is used in skin care products for its excellent skin penetration. The purpose of this study was to examine the anti-melanogenic effects of resveratryl triglycolate (RTG), a novel hybrid compound of resveratrol and GA, in comparison with resveratrol, GA, resveratryl triacetate (RTA) and arbutin. Resveratrol, RTG, and RTA inhibited the catalytic activity human tyrosinase (TYR) more potently than arbutin or GA did. Their cytotoxic and anti-melanogenic effects were examined using murine melanoma B16/F10 cells and human epidermal melanocytes (HEMs). The cytotoxicity of RTG was similar to that of resveratrol and RTA. RTG at 3-10 μM decreased melanin levels and cellular TYR activities in α-melanocyte-stimulating hormone-stimulated B16/F10 cells, and L-tyrosine-stimulated HEMs. RTG also suppressed mRNA and protein expression of TYR, tyrosinase-related protein 1, L-3,4-dihydroxyphenylalanine chrome tautomerase, and microphthalmia-associated transcription factor (MITF) in HEMs stimulated with L-tyrosine. This study suggests that, like resveratrol and RTA, RTG can attenuate cellular melanin synthesis effectively through the suppression of MITF-dependent expression of melanogenic enzymes and the inhibition of catalytic activity of TYR enzyme. RTG therefore has potential for use as a cosmeceutical ingredient for skin whitening. PMID:27059716

  19. Telomerization of amino acids with butadiene, catalyzed by palladium complexes

    SciTech Connect

    Dzhemilev, U.M.; Fakhretdinov, R.N.; Telin, A.G.

    1987-01-10

    The telomerization of ..cap alpha..-, ..beta..-, ..gamma..-, and epsilon-amino acids having various structures with butadiene under the influence of the three-component palladium catalyst Pd(acac)/sub 2/-PPh/sub 3/-AlEt/sub 3/ was investigated in DMSO-toluene solution. The ..cap alpha..- and epsilon-aliphatic and also the ..cap alpha..-, ..beta..-, and ..gamma..-aromatic amino acids react with butadiene, giving the products from octadienylation at the amino group exclusively. Under the conditions of telomerization aliphatic ..beta..-amino acids are cleaved with the formation of unsaturated tertiary amines. In the case of aliphatic ..gamma..-amino acids it is possible to obtain telomers alkylated at the carbonyl group.

  20. A mild copper-catalyzed aerobic oxidative thiocyanation of arylboronic acids with TMSNCS.

    PubMed

    Sun, Nan; Che, Liusheng; Mo, Weimin; Hu, Baoxiang; Shen, Zhenlu; Hu, Xinquan

    2015-01-21

    A facile and efficient transformation of arylboronic acids to their corresponding aryl thiocyanates has been successfully developed. Based on the CuCl-catalyzed oxidative cross-coupling reaction between arylboronic acids and trimethylsilylisothiocyanate (TMSNCS) under oxygen atmosphere, the transformation can be readily conducted at ambient temperature. The newly-developed protocol provided a competitive synthetic approach to aryl thiocyanates that can tolerate a broad range of reactive functional groups and/or strong electron-withdrawing groups. PMID:25514847

  1. Copper-assisted palladium(II)-catalyzed direct arylation of cyclic enaminones with arylboronic acids.

    PubMed

    Kim, Yong Wook; Niphakis, Micah J; Georg, Gunda I

    2012-11-01

    Described herein is a palladium(II)-catalyzed direct arylation of cyclic enaminones with arylboronic acids. The versatility of this method is that both electron-rich and electron-poor boronic acids can be coupled in high yields. A mixture of two Cu(II) additives was crucial for efficient cross-coupling. The role of each Cu(II) reagent appears to be distinct and complementary serving to assist catalyst reoxidation and transmetalation through a putative arylcopper intermediate. PMID:23088256

  2. On the Brønsted acid-catalyzed homogeneous hydrolysis of furans.

    PubMed

    Nikbin, Nima; Caratzoulas, Stavros; Vlachos, Dionisios G

    2013-11-01

    Furan affairs: Electronic structure calculations of the homogeneous Brønsted acid-catalyzed hydrolysis of 2,5-dimethylfuran show that proton transfer to the β-position is rate-limiting and provides support that the hydrolysis follows general acid catalysis. By means of projected Fukui indices, we show this to be the case for unsubstituted, 2-, and 2,5-substituted furans with electron-donating groups.

  3. Lewis Acid Catalyzed Selective Reactions of Donor-Acceptor Cyclopropanes with 2-Naphthols.

    PubMed

    Kaicharla, Trinadh; Roy, Tony; Thangaraj, Manikandan; Gonnade, Rajesh G; Biju, Akkattu T

    2016-08-16

    Lewis acid-catalyzed reactions of 2-substituted cyclopropane 1,1-dicarboxylates with 2-naphthols is reported. The reaction exhibits tunable selectivity depending on the nature of Lewis acid employed and proceed as a dearomatization/rearomatization sequence. With Bi(OTf)3 as the Lewis acid, a highly selective dehydrative [3+2] cyclopentannulation takes place leading to the formation of naphthalene-fused cyclopentanes. Interestingly, engaging Sc(OTf)3 as the Lewis acid, a Friedel-Crafts-type addition of 2-naphthols to cyclopropanes takes place, thus affording functionalized 2-naphthols. Both reactions furnished the target products in high regioselectivity and moderate to high yields. PMID:27391792

  4. Particle growth by acid-catalyzed heterogeneous reactions of organic carbonyls on preexisting aerosols.

    PubMed

    Jang, Myoseon; Carroll, Brian; Chandramouli, Bharadwaj; Kamens, Richard M

    2003-09-01

    Aerosol growth by the heterogeneous reactions of different aliphatic and alpha,beta-unsaturated carbonyls in the presence/absence of acidified seed aerosols was studied in a 2 m long flow reactor (2.5 cm i.d.) and a 0.5-m3 Teflon film bag under darkness. For the flow reactor experiments, 2,4-hexadienal, 5-methyl-3-hexen-2-one, 2-cyclohexenone, 3-methyl-2-cyclopentenone, 3-methyl-2-cyclohexenone, and octanal were studied. The carbonyls were selected based on their reactivity for acid-catalyzed reactions, their proton affinity, and their similarity to the ring-opening products from the atmospheric oxidation of aromatics. To facilitate acid-catalyzed heterogeneous hemiacetal/acetal formation, glycerol was injected along with inorganic seed aerosols into the flow reactor system. Carbonyl heterogeneous reactions were accelerated in the presence of acid catalysts (H2SO4), leading to higher aerosol yields than in their absence. Aldehydes were more reactive than ketones for acid-catalyzed reactions. The conjugated functionality also resulted in higher organic aerosol yieldsthan saturated aliphatic carbonyls because conjugation with the olefinic bond increases the basicity of the carbonyl leading to increased stability of the protonated carbonyl. Aerosol population was measured from a series of sampling ports along the length of the flow reactor using a scanning mobility particle sizer. Fourier transform infrared spectrometry of either an impacted liquid aerosol layer or direct reaction of carbonyls as a thin liquid layer on a zinc selenide FTIR disk was employed to demonstrate the direct transformation of chemical functional groups via the acid-catalyzed reactions. These results strongly indicate that atmospheric multifunctional organic carbonyls, which are created by atmospheric photooxidation reactions, can contribute significantly to secondary organic aerosol formation through acid-catalyzed heterogeneous reactions. Exploratory studies in 25- and 190-m3 outdoor chambers

  5. Ursolic acid from Plantago major, a selective inhibitor of cyclooxygenase-2 catalyzed prostaglandin biosynthesis.

    PubMed

    Ringbom, T; Segura, L; Noreen, Y; Perera, P; Bohlin, L

    1998-10-01

    A hexane extract of Plantago major was investigated by bioactivity-directed fractionation, using an in vitro cyclooxygenase-2 (COX-2) catalyzed prostaglandin biosynthesis inhibition assay, and resulted in the isolation of ursolic acid (1). This triterpenoid showed a significant COX-2 inhibitory effect, directly on the enzyme activity, with an IC50 value of 130 microM and a COX-2/COX-1 selectivity ratio of 0.6. The structural isomer oleanolic acid (2) was found to be less active than 1, with an IC50 value of 295 microM, but showed a similar selectivity ratio (0.8). Furthermore, no significant inhibition on COX-2 or COX-1 was observed by the triterpenoid, 18beta-glycyrrhetinic acid (3). The direct inhibitory effect of 1 and 2 on COX-2 catalyzed prostaglandin biosynthesis increased with preincubation, indicating a time-dependent inhibition, while the effect on COX-1 was found to be independent of preincubation time.

  6. Choline Chloride Catalyzed Amidation of Fatty Acid Ester to Monoethanolamide: A Green Approach.

    PubMed

    Patil, Pramod; Pratap, Amit

    2016-01-01

    Choline chloride catalyzed efficient method for amidation of fatty acid methyl ester to monoethanolamide respectively. This is a solvent free, ecofriendly, 100% chemo selective and economically viable path for alkanolamide synthesis. The Kinetics of amidation of methyl ester were studied and found to be first order with respect to the concentration of ethanolamine. The activation energy (Ea) for the amidation of lauric acid methyl ester catalyzed by choline chloride was found to be 50.20 KJ mol(-1). The 98% conversion of lauric acid monoethanolamide was obtained at 110°C in 1 h with 6% weight of catalyst and 1:1.5 molar ratio of methyl ester to ethanolamine under nitrogen atmosphere. PMID:26666271

  7. Scope of the Palladium-Catalyzed Aryl Borylation Utilizing Bis-Boronic Acid

    PubMed Central

    Molander, Gary A.; Trice, Sarah L. J.; Kennedy, Steven M.; Dreher, Spencer D.; Tudge, Matthew T.

    2012-01-01

    The Suzuki-Miyaura reaction has become one of the more useful tools for synthetic organic chemists. Until recently, there did not exist a direct way to make the most important component in the coupling reaction, namely the boronic acid. Current methods to make boronic acids often employ harsh or wasteful reagents to prepare boronic acid derivatives and require additional steps to afford the desired boronic acid. The scope of the previously reported palladium-catalyzed, direct boronic acid synthesis is unveiled, which includes a wide array of synthetically useful aryl electrophiles. It makes use of the newly available second generation Buchwald XPhos preformed palladium catalyst and bis-boronic acid (BBA). For ease of isolation and to preserve the often sensitive C-B bond, all boronic acids were readily converted to their more stable trifluoroborate counterparts. PMID:22769742

  8. Enantioselective Rh(I)-Catalyzed Addition of Arylboronic Acids to Cyclic Ketimines.

    PubMed

    Kong, Jongrock; McLaughlin, Mark; Belyk, Kevin; Mondschein, Ryan

    2015-11-20

    A method for the enantioselective synthesis of chiral α-tertiary amines via Rh-catalyzed 1,2-addition of arylboronic acids to cyclic ketimines is described. The products are efficiently accessed in good yields and excellent enantioselectivities using a commercially available chiral ligand. The reaction scope includes vinyl, aryl, and heteroarylboronic acids with yields ranging from 40% to 99% and enantiomeric excesses from 88% to 99%. Conversion of an addition product into an α,α-diaryl-substituted amino acid is also demonstrated.

  9. Organosolv liquefaction of sugarcane bagasse catalyzed by acidic ionic liquids.

    PubMed

    Chen, Zhengjian; Long, Jinxing

    2016-08-01

    An efficient and eco-friendly process is proposed for sugarcane bagasse liquefaction under mild condition using IL catalyst and environmental friendly solvent of ethanol/H2O. The relationship between IL acidic strength and its catalytic performance is investigated. The effects of reaction condition parameters such as catalyst dosage, temperature, time and solvent are also intensively studied. The results show that ethanol/H2O has a significant promotion effect on the simultaneous liquefaction of sugarcane bagasse carbohydrate and lignin. 97.5% of the bagasse can be liquefied with 66.46% of volatile product yield at 200°C for 30min. Furthermore, the IL catalyst shows good recyclability where no significant loss of the catalytic activity is exhibited even after five runs. PMID:27115746

  10. Organosolv liquefaction of sugarcane bagasse catalyzed by acidic ionic liquids.

    PubMed

    Chen, Zhengjian; Long, Jinxing

    2016-08-01

    An efficient and eco-friendly process is proposed for sugarcane bagasse liquefaction under mild condition using IL catalyst and environmental friendly solvent of ethanol/H2O. The relationship between IL acidic strength and its catalytic performance is investigated. The effects of reaction condition parameters such as catalyst dosage, temperature, time and solvent are also intensively studied. The results show that ethanol/H2O has a significant promotion effect on the simultaneous liquefaction of sugarcane bagasse carbohydrate and lignin. 97.5% of the bagasse can be liquefied with 66.46% of volatile product yield at 200°C for 30min. Furthermore, the IL catalyst shows good recyclability where no significant loss of the catalytic activity is exhibited even after five runs.

  11. Enantioselective aldol reaction between isatins and cyclohexanone catalyzed by amino acid sulphonamides.

    PubMed

    Wang, Jun; Liu, Qi; Hao, Qing; Sun, Yanhua; Luo, Yiming; Yang, Hua

    2015-04-01

    Sulphonamides derived from primary α-amino acid were successfully applied to catalyze the aldol reaction between isatin and cyclohexanone under neat conditions. More interestingly, molecular sieves, as privileged additives, were found to play a vital role in achieving high enantioselectivity. Consequently, high yields (up to 99%) along with good enantioselectivities (up to 92% ee) and diastereoselectivities (up to 95:5 dr) were obtained. In addition, this reaction was also conveniently scaled up, demonstrating the applicability of this protocol.

  12. One site is enough: a theoretical investigation of iron-catalyzed dehydrogenation of formic Acid.

    PubMed

    Sánchez-de-Armas, Rocío; Xue, Liqin; Ahlquist, Mårten S G

    2013-09-01

    Dehydrogenation of HCO2H: The reaction mechanism for the dehydrogenation of formic acid catalyzed by a highly active and selective iron complex has been studied by DFT. The most favorable pathway shows the hydride in Fe-H complexes acting as a spectator ligand throughout the catalytic cycle. This result opens up the Fe complex for modification in order to achieve more efficient and selective catalysts. PMID:23907850

  13. Boron-Catalyzed N-Alkylation of Amines using Carboxylic Acids.

    PubMed

    Fu, Ming-Chen; Shang, Rui; Cheng, Wan-Min; Fu, Yao

    2015-07-27

    A boron-based catalyst was found to catalyze the straightforward alkylation of amines with readily available carboxylic acids in the presence of silane as the reducing agent. Various types of primary and secondary amines can be smoothly alkylated with good selectivity and good functional-group compatibility. This metal-free amine alkylation was successfully applied to the synthesis of three commercial medicinal compounds, Butenafine, Cinacalcet. and Piribedil, in a one-pot manner without using any metal catalysts. PMID:26150397

  14. Brønsted Acid-Catalyzed Cascade Reactions Involving 1,2-Indole Migration.

    PubMed

    Álvarez, Estela; Nieto Faza, Olalla; Silva López, Carlos; Fernández-Rodríguez, Manuel A; Sanz, Roberto

    2015-09-01

    A cascade reaction of indoles with propargylic diols involving an unprecedented metal-free 1,2-indole migration onto an alkyne was carried out. DFT calculations support a mechanism consisting of a concerted nucleophilic attack of the indole nucleus with loss of water, followed by the 1,2-migration and subsequent Nazarov cyclization. This Brønsted acid-catalyzed protocol affords indole-functionalized benzofulvene derivatives in high yields. PMID:26211757

  15. Boron-Catalyzed N-Alkylation of Amines using Carboxylic Acids.

    PubMed

    Fu, Ming-Chen; Shang, Rui; Cheng, Wan-Min; Fu, Yao

    2015-07-27

    A boron-based catalyst was found to catalyze the straightforward alkylation of amines with readily available carboxylic acids in the presence of silane as the reducing agent. Various types of primary and secondary amines can be smoothly alkylated with good selectivity and good functional-group compatibility. This metal-free amine alkylation was successfully applied to the synthesis of three commercial medicinal compounds, Butenafine, Cinacalcet. and Piribedil, in a one-pot manner without using any metal catalysts.

  16. Origins of Selectivity and General Model for Chiral Phosphoric Acid-Catalyzed Oxetane Desymmetrizations.

    PubMed

    Champagne, Pier Alexandre; Houk, K N

    2016-09-28

    The origins of the high enantioselectivity of chiral phosphoric acid-catalyzed oxetane desymmetrizations were investigated by density functional theory (DFT) calculations. Distortion of the catalyst structure, caused by steric crowding in the catalyst pocket of one enantiomeric transition state, is the main cause for stereochemical preference. A general model was developed to assist in the rational design of new catalysts for related transformations. PMID:27629045

  17. Acetic acid-catalyzed formation of N-phenylphthalimide from phthalanilic acid: a computational study of the mechanism.

    PubMed

    Takahashi, Ohgi; Kirikoshi, Ryota; Manabe, Noriyoshi

    2015-05-28

    In glacial acetic acid, phthalanilic acid and its monosubstituents are known to be converted to the corresponding phthalimides in relatively good yields. In this study, we computationally investigated the experimentally proposed two-step (addition-elimination or cyclization-dehydration) mechanism at the second-order Møller-Plesset perturbation (MP2) level of theory for the unsubstituted phthalanilic acid, with an explicit acetic acid molecule included in the calculations. In the first step, a gem-diol tetrahedral intermediate is formed by the nucleophilic attack of the amide nitrogen. The second step is dehydration of the intermediate to give N-phenylphthalimide. In agreement with experimental findings, the second step has been shown to be rate-determining. Most importantly, both of the steps are catalyzed by an acetic acid molecule, which acts both as proton donor and acceptor. The present findings, along with those from our previous studies, suggest that acetic acid and other carboxylic acids (in their undissociated forms) can catalyze intramolecular nucleophilic attacks by amide nitrogens and breakdown of the resulting tetrahedral intermediates, acting simultaneously as proton donor and acceptor. In other words, double proton transfers involving a carboxylic acid molecule can be part of an extensive bond reorganization process from cyclic hydrogen-bonded complexes.

  18. Acetic Acid Can Catalyze Succinimide Formation from Aspartic Acid Residues by a Concerted Bond Reorganization Mechanism: A Computational Study

    PubMed Central

    Takahashi, Ohgi; Kirikoshi, Ryota; Manabe, Noriyoshi

    2015-01-01

    Succinimide formation from aspartic acid (Asp) residues is a concern in the formulation of protein drugs. Based on density functional theory calculations using Ace-Asp-Nme (Ace = acetyl, Nme = NHMe) as a model compound, we propose the possibility that acetic acid (AA), which is often used in protein drug formulation for mildly acidic buffer solutions, catalyzes the succinimide formation from Asp residues by acting as a proton-transfer mediator. The proposed mechanism comprises two steps: cyclization (intramolecular addition) to form a gem-diol tetrahedral intermediate and dehydration of the intermediate. Both steps are catalyzed by an AA molecule, and the first step was predicted to be rate-determining. The cyclization results from a bond formation between the amide nitrogen on the C-terminal side and the side-chain carboxyl carbon, which is part of an extensive bond reorganization (formation and breaking of single bonds and the interchange of single and double bonds) occurring concertedly in a cyclic structure formed by the amide NH bond, the AA molecule and the side-chain C=O group and involving a double proton transfer. The second step also involves an AA-mediated bond reorganization. Carboxylic acids other than AA are also expected to catalyze the succinimide formation by a similar mechanism. PMID:25588215

  19. Sulfuric, hydrochloric, and nitric acid-catalyzed triacetone triperoxide (TATP) reaction mixtures: an aging study.

    PubMed

    Fitzgerald, Mark; Bilusich, Daniel

    2011-09-01

    The organic peroxide explosive triacetone triperoxide (TATP) is regularly encountered by law enforcement agents in various stages of its production. This study utilizes solid-phase microextraction (SPME) and gas chromatography/mass spectrometry (GC/MS) to examine sulfuric acid-, hydrochloric acid-, and nitric acid-catalyzed TATP syntheses during the initial 24 h of these reactions at low temperatures (5-9°C). Additionally, aging of the reaction mixtures was examined at both low and ambient temperatures (19-21°C) for a further 9 days. For each experiment, TATP could be readily identified in the headspace above the reaction mixture 1 h subsequent to the combination of reagents; at 24 h, TATP and diacetone diperoxide (DADP) were prominent. TATP degraded more rapidly than DADP. Additionally, chlorinated acetones chloroacetone and 1,1,-dichloroacetone were identified in the headspace above the hydrochloric acid-catalyzed TATP reaction mixture. These were not present when the catalyst was sulfuric acid or nitric acid. PMID:21595692

  20. Synthesis of Fused Polycyclic Indoles by Brønsted Acid-Catalyzed Intramolecular Alkylation of Indoles with Alcohols.

    PubMed

    Suárez, Anisley; Gohain, Mukut; Fernández-Rodríguez, Manuel A; Sanz, Roberto

    2015-10-16

    An efficient methodology for the synthesis of a series of new fused polyclyclic indoles has been developed by Brønsted acid-catalyzed intramolecular Friedel-Crafts reactions of properly designed indolyl alcohols. PMID:26418556

  1. Solid acid-catalyzed depolymerization of barley straw driven by ball milling.

    PubMed

    Schneider, Laura; Haverinen, Jasmiina; Jaakkola, Mari; Lassi, Ulla

    2016-04-01

    This study describes a time and energy saving, solvent-free procedure for the conversion of lignocellulosic barley straw into reducing sugars by mechanocatalytical pretreatment. The catalytic conversion efficiency of several solid acids was tested which revealed oxalic acid dihydrate as a potential catalyst with high conversion rate. Samples were mechanically treated by ball milling and subsequently hydrolyzed at different temperatures. The parameters of the mechanical treatment were optimized in order to obtain sufficient amount of total reducing sugar (TRS) which was determined following the DNS assay. Additionally, capillary electrophoresis (CE) and Fourier transform infrared spectrometry (FT-IR) were carried out. Under optimal conditions TRS 42% was released using oxalic acid dihydrate as a catalyst. This study revealed that the acid strength plays an important role in the depolymerization of barley straw and in addition, showed, that the oxalic acid-catalyzed reaction generates low level of the degradation product 5-hydroxymethylfurfural (HMF). PMID:26859328

  2. Copper-catalyzed intermolecular trifluoromethylarylation of alkenes: mutual activation of arylboronic acid and CF3+ reagent.

    PubMed

    Wang, Fei; Wang, Dinghai; Mu, Xin; Chen, Pinhong; Liu, Guosheng

    2014-07-23

    A novel copper-catalyzed intermolecular trifluoromethylarylation of alkenes is developed using less active ether-type Togni's reagent under mild reaction conditions. Various alkenes and diverse arylboronic acids are compatible with these conditions. Preliminary mechanistic studies reveal that a mutual activation process between arylboronic acid and CF3(+) reagent is essential. In addition, the reaction might involve a rate-determining transmetalation, and the final aryl C-C bond is derived from reductive elimination of the aryl(alkyl)Cu(III) intermediate. PMID:24983408

  3. Asymmetric epoxidation of allylic alcohols catalyzed by vanadium-binaphthylbishydroxamic Acid complex.

    PubMed

    Noji, Masahiro; Kobayashi, Toshihiro; Uechi, Yuria; Kikuchi, Asami; Kondo, Hisako; Sugiyama, Shigeo; Ishii, Keitaro

    2015-03-20

    A vanadium-binaphthylbishydroxamic acid (BBHA) complex-catalyzed asymmetric epoxidation of allylic alcohols is described. The optically active binaphthyl-based ligands BBHA 2a and 2b were synthesized from (S)-1,1'-binaphthyl-2,2'-dicarboxylic acid and N-substituted-O-trimethylsilyl (TMS)-protected hydroxylamines via a one-pot, three-step procedure. The epoxidations of 2,3,3-trisubstituted allylic alcohols using the vanadium complex of 2a were easily performed in toluene with a TBHP water solution to afford (2R)-epoxy alcohols in good to excellent enantioselectivities.

  4. A short scalable route to (-)-α-kainic acid using Pt-catalyzed direct allylic amination.

    PubMed

    Zhang, Ming; Watanabe, Kenji; Tsukamoto, Masafumi; Shibuya, Ryozo; Morimoto, Hiroyuki; Ohshima, Takashi

    2015-03-01

    An increased supply of scarce or inaccessible natural products is essential for the development of more sophisticated pharmaceutical agents and biological tools, and thus the development of atom-economical, step-economical and scalable processes to access these natural products is in high demand. Herein we report the development of a short, scalable total synthesis of (-)-α-kainic acid, a useful compound in neuropharmacology that is, however, limited in supply from natural resources. The synthesis features sequential platinum-catalyzed direct allylic aminations and thermal ene-cyclization, enabling the gram-scale synthesis of (-)-α-kainic acid in six steps and 34% overall yield. PMID:25604395

  5. Lewis super-acid catalyzed cyclizations: a new route to fragrance compounds.

    PubMed

    Coulombel, Lydie; Grau, Fanny; Weïwer, Michel; Favier, Isabelle; Chaminade, Xavier; Heumann, Andreas; Bayón, J Carles; Aguirre, Pedro A; Duñach, Elisabet

    2008-06-01

    This review deals with the application of Lewis super acids such as Al(III), In(III), and Sn(IV) triflates and triflimidates as catalysts in the synthesis of fragrance materials. Novel catalytic reactions involving C-C and C-heteroatom bond-forming reactions, as well as cycloisomerization processes are presented. In particular, Sn(IV) and Al(III) triflates were employed as catalysts in the selective cyclization of unsaturated alcohols to cyclic ethers, as well as in the cyclization of unsaturated carboxylic acids to lactones. The addition of thiols and thioacids to non-activated olefins, both in intra- and intermolecular versions, was efficiently catalyzed by In(III) derivatives. Sn(IV) Triflimidates catalyzed the cycloisomerization of highly substituted 1,6-dienes to gem-dimethyl-substituted cyclohexanes bearing an isopropylidene substituent. The hydroformylation of these unsaturated substrates, catalyzed by a Rh(I) complex with a bulky phosphite ligand, selectively afforded the corresponding linear aldehydes. The olfactory evaluation of selected heterocycles, carbocycles, and aldehydes synthesized is also discussed.

  6. Formation of linear polyenes in poly(vinyl alcohol) films catalyzed by phosphotungstic acid, aluminum chloride, and hydrochloric acid

    NASA Astrophysics Data System (ADS)

    Tretinnikov, O. N.; Sushko, N. I.; Malyi, A. B.

    2016-07-01

    Formation of linear polyenes-(CH=CH)n-via acid-catalyzed thermal dehydration of polyvinyl alcohol in 9- to 40-µm-thick films of this polymer containing hydrochloric acid, aluminum chloride, and phosphotungstic acid as dehydration catalysts was studied by electronic absorption spectroscopy. The concentration of long-chain ( n ≥ 8) polyenes in films containing phosphotungstic acid is found to monotonically increase with the duration of thermal treatment of films, although the kinetics of this process is independent of film thickness. In films containing hydrochloric acid and aluminum chloride, the formation rate of polyenes with n ≥ 8 rapidly drops as film thickness decreases and the annealing time increases. As a result, at a film thickness of less than 10-12 µm, long-chain polyenes are not formed at all in these films no matter how long thermal duration is. The reason for this behavior is that hydrochloric acid catalyzing polymer dehydration in these films evaporates from the films during thermal treatment, the evaporation rate inversely depending on film thickness.

  7. [Asymmetric synthesis of aromatic L-amino acids catalyzed by transaminase].

    PubMed

    Xia, Wenna; Sun, Yu; Min, Cong; Han, Wei; Wu, Sheng

    2012-11-01

    Aromatic L-Amino acids are important chiral building blocks for the synthesis of many drugs, pesticides, fine chemicals and food additives. Due to the high activity and steroselectivity, enzymatic synthesis of chiral building blocks has become the main research direction in asymmetric synthesis field. Guided by the phylogenetic analysis of transaminases from different sources, two representative aromatic transaminases TyrB and Aro8 in type I subfamily, from the prokaryote Escherichia coli and eukaryote Saccharomyces cerevisia, respectively, were applied for the comparative study of asymmetric transamination reaction process and catalytic efficiency of reversely converting keto acids to the corresponding aromatic L-amino acid. Both TyrB and Aro8 could efficiently synthesize the natural aromatic amino acids phenylalanine and tyrosine as well as non-natural amino acid phenylglycine. The chiral HPLC analysis showed the produced amino acids were L-configuration and the e.e value was 100%. L-alanine was the optimal amino donor, and the transaminase TyrB and Aro8 could not use D-amino acids as amino donor. The optimal molar ratio of amino donor (L-alanine) and amino acceptor (aromatic alpha-keto acids) was 4:1. Both of the substituted group on the aromatic ring and the length of fatty acid carbon chain part in the molecular structure of aromatic substrate alpha-keto acid have the significant impact on the enzyme-catalyzed transamination efficiency. In the experiments of preparative-scale transamination synthesis of L-phenylglycine, L-phenylalanine and L-tyrosine, the specific production rate catalyzed by TryB were 0.28 g/(g x h), 0.31 g/(g x h) and 0.60 g/(g x h) and the specific production rate catalyzed by Aro8 were 0.61 g/(g x h), 0.48 g/(g x h) and 0.59 g/(g x h). The results obtained here were useful for applying the transaminases to asymmetric synthesis of L-amino acids by reversing the reaction balance in industry.

  8. Bronsted Acid Catalyzed Dehydration of Neat Supercritical tert-Butanol in a Capillary Micro-Reactor

    SciTech Connect

    Henry, Matthew C.; Yonker, Clement R.

    2006-02-01

    Dehydration of supercritical t-butanol to yield 2-methyl-propene was observed to occur rapidly and in high yield at elevated pressures without addition of a catalyst. A capillary micro-reactor was used to carry out the reaction at pressures up to 3.1 kbar. The products were characterized in-situ using FTIR, GC-MS and NMR. The dehydration reaction is proposed to occur by a self-catalyzed Bronsted acid mechanism. An addition driving force for the reaction was the phase separation of the 2-methyl-propene product. Self-catalyzed dehydration of t-butanol is a limiting factor for operations in supercritical t-butanol, but it implies the t-butanol may be employed as a self-neutralizing catalyst under these conditions.

  9. Lipid extraction and esterification for microalgae-based biodiesel production using pyrite (FeS2).

    PubMed

    Seo, Yeong Hwan; Sung, Mina; Oh, You-Kwan; Han, Jong-In

    2015-09-01

    In this study, pyrite (FeS2) was used for lipid extraction as well as esterification processes for microalgae-based biodiesel production. An iron-mediated oxidation reaction, Fenton-like reaction, produced an expected degree of lipid extraction, but pyrite was less effective than FeCl3 commercial powder. That low efficiency was improved by using oxidized pyrite, which showed an equivalent lipid extraction efficiency to FeCl3, about 90%, when 20 mM of catalyst was used. Oxidized pyrite was also employed in the esterification step, and converted free fatty acids to fatty acid methyl esters under acidic conditions; thus, the fatal problem of saponification during esterification with alkaline catalysts was avoided, and esterification efficiency over 90% was obtained. This study clearly showed that pyrite could be utilized as a cheap catalyst in the lipid extraction and esterification steps for microalgae-based biodiesel production.

  10. Rhodium-catalyzed asymmetric addition of arylboronic acids to cyclic N-sulfonyl ketimines towards the synthesis of α,α-diaryl-α-amino acid derivatives.

    PubMed

    Takechi, Ryosuke; Nishimura, Takahiro

    2015-05-01

    Rhodium/chiral diene complex-catalyzed asymmetric addition of arylboronic acids to cyclic ketimines having an ester group proceeded to give the corresponding α-amino acid derivatives in high yields with high enantioselectivity. The cyclic amino acid derivative was transformed into a linear α,α-diaryl-substituted α-N-methylamino acid ester.

  11. Catalytic synthesis of biodiesel from high free fatty acid-containing feedstocks

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Recyclable and reusable heterogeneous diarylammonium catalysts are highly effective in catalyzing the esterification of the free fatty acid (FFA) present in greases to methyl esters to reduce the FFA content from 12-40 wt% to 0.5 – 1 wt%. The resulting ester-glyceride mixture (pretreated grease) co...

  12. Study of Soybean Oil Hydrolysis Catalyzed by Thermomyces lanuginosus Lipase and Its Application to Biodiesel Production via Hydroesterification

    PubMed Central

    Cavalcanti-Oliveira, Elisa d'Avila; da Silva, Priscila Rufino; Ramos, Alessandra Peçanha; Aranda, Donato Alexandre Gomes; Freire, Denise Maria Guimarães

    2011-01-01

    The process of biodiesel production by the hydroesterification route that is proposed here involves a first step consisting of triacylglyceride hydrolysis catalyzed by lipase from Thermomyces lanuginosus (TL 100L) to generate free fatty acids (FFAs). This step is followed by esterification of the FFAs with alcohol, catalyzed by niobic acid in pellets or without a catalyst. The best result for the enzyme-catalyzed hydrolysis was obtained under reaction conditions of 50% (v/v) soybean oil and 2.3% (v/v) lipase (25 U/mL of reaction medium) in distilled water and at 60°C; an 89% conversion rate to FFAs was obtained after 48 hours of reaction. For the esterification reaction, the best result was with an FFA/methanol molar ratio of 1:3, niobic acid catalyst at a concentration of 20% (w/w FFA), and 200°C, which yielded 92% conversion of FFAs to soy methyl esters after 1 hour of reaction. This study is exceptional because both the hydrolysis and the esterification use a simple reaction medium with high substrate concentrations. PMID:21052517

  13. Salicylic acid-induced superoxide generation catalyzed by plant peroxidase in hydrogen peroxide-independent manner.

    PubMed

    Kimura, Makoto; Kawano, Tomonori

    2015-01-01

    It has been reported that salicylic acid (SA) induces both immediate spike and long lasting phases of oxidative burst represented by the generation of reactive oxygen species (ROS) such as superoxide anion radical (O2(•-)). In general, in the earlier phase of oxidative burst, apoplastic peroxidase are likely involved and in the late phase of the oxidative burst, NADPH oxidase is likely involved. Key signaling events connecting the 2 phases of oxidative burst are calcium channel activation and protein phosphorylation events. To date, the known earliest signaling event in response to exogenously added SA is the cell wall peroxidase-catalyzed generation of O2(•-) in a hydrogen peroxide (H2O2)-dependent manner. However, this model is incomplete since the source of the initially required H2O2 could not be explained. Based on the recently proposed role for H2O2-independent mechanism for ROS production catalyzed by plant peroxidases (Kimura et al., 2014, Frontiers in Plant Science), we hereby propose a novel model for plant peroxidase-catalyzed oxidative burst fueled by SA.

  14. The Acid Catalyzed Nitration of Methanol: Formation of Methyl Nitrate via Aerosol Chemistry

    NASA Technical Reports Server (NTRS)

    Riffel, Brent G.; Michelsen, Rebecca R.; Iraci, Laura T.

    2004-01-01

    The liquid phase acid catalyzed reaction of methanol with nitric acid to yield methyl nitrate under atmospheric conditions has been investigated using gas phase infrared spectroscopy. This nitration reaction is expected to occur in acidic aerosol particles found in the upper troposphere/lower stratosphere as highly soluble methanol and nitric acid diffuse into these aerosols. Gaseous methyl nitrate is released upon formation, suggesting that some fraction of NO(x) may he liberated from nitric acid (methyl nitrate is later photolyzed to NO(x)) before it is removed from the atmosphere by wet deposition. Thus, this reaction may have important implications for the NO(x) budget. Reactions have been initiated in 45-62 wt% H2SO4 solutions at 10.0 C. Methyl nitrate production rates increased exponentially with acidity within the acidity regime studied. Preliminary calculations suggest that the nitronium ion (NO2(+) is the active nitrating agent under these conditions. The reaction order in methanol appears to depend on the water/methanol ratio and varies from first to zeroth order under conditions investigated. The nitration is first order in nitronium at all acidities investigated. A second order rate constant, kappa(sub 2), has been calculated to be 1 x 10(exp 8)/ M s when the reaction is first order in methanol. Calculations suggest the nitration is first order in methanol under tropospheric conditions. The infinitesimal percentage of nitric acid in the nitronium ion form in this acidity regime probably makes this reaction insignificant for the upper troposphere; however, this nitration may become significant in the mid stratosphere where colder temperatures increase nitric acid solubility and higher sulfuric acid content shifts nitric acid speciation toward the nitronium ion.

  15. Kinetic mechanism and structural requirements of the amine-catalyzed decarboxylation of oxaloacetic acid.

    PubMed

    Thalji, Nabil K; Crowe, William E; Waldrop, Grover L

    2009-01-01

    The kinetic and chemical mechanism of amine-catalyzed decarboxylation of oxaloacetic acid at pH 8.0 has been reevaluated using a new and versatile assay. Amine-catalyzed decarboxylation of oxaloacetic acid proceeds via the formation of an imine intermediate, followed by decarboxylation of the intermediate and hydrolysis to yield pyruvate. The decrease in oxaloacetic acid was coupled to NADH formation by malate dehydrogenase, which allowed the rates of both initial carbinolamine formation (as part of the imination step) and decarboxylation to be determined. By comparing the rates observed for a variety of amines and, in particular, diamines, the structural and electronic requirements for diamine-catalyzed decarboxylation at pH 8.0 were identified. At pH 8.0, monoamines were found to be very poor catalysts, whereas some diamines, most notably ethylenediamine, were excellent catalysts. The results indicate that the second amino group of diamines enhances the rate of imine formation by acting as a proton shuttle during the carbinolamine formation step, which enables diamines to overcome high levels of solvation that would otherwise inhibit carbinolamine, and thus imine, formation. The presence of the second amino group may also enhance the rate of the carbinolamine dehydration step. In contrast to the findings of previous reports, the second amino group participates in the reaction by enhancing the rate of decarboxylation via hydrogen-bonding to the imine nitrogen to either stabilize the negative charge that develops on the imine during decarboxylation or preferentially stabilize the reactive imine over the unreactive enamine tautomer. These results provide insight into the precise catalytic mechanism of several enzymes whose reactions are known to proceed via an imine intermediate.

  16. Optimization and kinetic modeling of esterification of the oil obtained from waste plum stones as a pretreatment step in biodiesel production.

    PubMed

    Kostić, Milan D; Veličković, Ana V; Joković, Nataša M; Stamenković, Olivera S; Veljković, Vlada B

    2016-02-01

    This study reports on the use of oil obtained from waste plum stones as a low-cost feedstock for biodiesel production. Because of high free fatty acid (FFA) level (15.8%), the oil was processed through the two-step process including esterification of FFA and methanolysis of the esterified oil catalyzed by H2SO4 and CaO, respectively. Esterification was optimized by response surface methodology combined with a central composite design. The second-order polynomial equation predicted the lowest acid value of 0.53mgKOH/g under the following optimal reaction conditions: the methanol:oil molar ratio of 8.5:1, the catalyst amount of 2% and the reaction temperature of 45°C. The predicted acid value agreed with the experimental acid value (0.47mgKOH/g). The kinetics of FFA esterification was described by the irreversible pseudo first-order reaction rate law. The apparent kinetic constant was correlated with the initial methanol and catalyst concentrations and reaction temperature. The activation energy of the esterification reaction slightly decreased from 13.23 to 11.55kJ/mol with increasing the catalyst concentration from 0.049 to 0.172mol/dm(3). In the second step, the esterified oil reacted with methanol (methanol:oil molar ratio of 9:1) in the presence of CaO (5% to the oil mass) at 60°C. The properties of the obtained biodiesel were within the EN 14214 standard limits. Hence, waste plum stones might be valuable raw material for obtaining fatty oil for the use as alternative feedstock in biodiesel production.

  17. Acid-catalyzed furfurly alcohol polymerization : characterizations of molecular structure and thermodynamic properties.

    SciTech Connect

    Kim, T.; Assary, R. S.; Marshall, C. L.; Gosztola, D. J.; Curtiss, L. A.; Stair, P. C.

    2011-01-01

    The liquid-phase polymerization of furfuryl alcohol catalyzed by sulfuric acid catalysts and the identities of molecular intermediates were investigated by using Raman spectroscopy and density functional theory calculation. At room temperature, with an acid catalyst, a vigorous furfuryl alcohol polymerization reaction was observed, whereas even at a high water concentration, furfuryl alcohol was very stable in the absence of an acid catalyst. Theoretical studies were carried out to investigate the thermodynamics of protonation of furfuryl alcohol, initiation of polymerization, and formation of conjugated dienes and diketonic species by using the B3LYP level of theory. A strong aliphatic C=C band observed in the calculated and measured Raman spectra provided crucial evidence to understand the polymerization reaction mechanism. It is confirmed that the formation of a conjugated diene structure rather than a diketone structure is involved in the furfuryl alcohol polymerization reaction.

  18. Acid-catalyzed Furfuryl Alcohol Polymerization: Characterizations of Molecular Structure and Thermodynamic Properties

    SciTech Connect

    Kim, Taejin; Assary, Rajeev A.; Marshall, Christopher L.; Gosztola, David J.; Curtiss, Larry A.; Stair, Peter C.

    2011-07-22

    The liquid-phase polymerization of furfuryl alcohol catalyzed by sulfuric acid catalysts and the identities of molecular intermediates were investigated by using Raman spectroscopy and density functional theory calculation. At room temperature, with an acid catalyst, a vigorous furfuryl alcohol polymerization reaction was observed, whereas even at a high water concentration, furfuryl alcohol was very stable in the absence of an acid catalyst. Theoretical studies were carried out to investigate the thermodynamics of protonation of furfuryl alcohol, initiation of polymerization, and formation of conjugated dienes and diketonic species by using the B3LYP level of theory. A strong aliphatic C=C band observed in the calculated and measured Raman spectra provided crucial evidence to understand the polymerization reaction mechanism. It is confirmed that the formation of a conjugated diene structure rather than a diketone structure is involved in the furfuryl alcohol polymerization reaction.

  19. Approach to Merosesquiterpenes via Lewis Acid Catalyzed Nazarov-Type Cyclization: Total Synthesis of Akaol A.

    PubMed

    Kakde, Badrinath N; Kumar, Nivesh; Mondal, Pradip Kumar; Bisai, Alakesh

    2016-04-15

    A Lewis acid catalyzed Nazarov-type cyclization of arylvinylcarbinol has been developed for the asymmetric synthesis of carbotetracyclic core of merosesquiterpenes. The reaction works only in the presence of 2 mol % of Sn(OTf)2 and Bi(OTf)3 in dichloroethane under elevated temperature. The methodology offers the synthesis of a variety of enantioenriched arylvinylcarbinols from commercially available (3aR)-sclareolide 9 in six steps with an eventual concise total synthesis of marine sesquiterpene quinol, akaol A (1a). PMID:27028314

  20. Kinetic and process studies on free and solid acid catalyzed hydrolysis of biomass substrates

    SciTech Connect

    Abasaeed, A.E.

    1987-01-01

    Trifluoroacetic acid (TFA) was tested as a catalyst for cellulose hydrolysis. Eighty percent conversion of cellulose into glucose was obtained with concentrated TFA. The kinetics of TFA catalyzed cellulose hydrolysis was investigated. The reaction was found to follow first order kinetics for both hydrolysis and decomposition. The kinetic parameters were determined from experimental data covering conditions of 160-180 C, 10-30% acid, and 1:2 solid to liquid ratio. The hydrolysis reaction was found to be more sensitive to temperature than the decomposition reaction. Use of TFA was further investigated as a pretreatment for enzymatic hydrolysis of cellulose. A two-fold increase in sugar yields was obtained for TFA pretreated samples in comparison to untreated ones. The kinetics of hydrolysis of prehydrolyzed wood by sulfuric acid was investigated. The substrate was first treated with 0.75% acid at 184 C for 4 minutes to remove hemicellulose. The kinetic parameters were determined in the range of 198-215 C and 1-3% acid. A heterogeneous kinetic model was developed to study the effect of particle size on acid hydrolysis of cellulose. It was found that as the chip size increases, maximum glucose yield decreases and reaction time at which maximum yield occurs increases. Acidic zeolites (LZ-M-8) were investigated as catalysts for hydrolysis reaction of inulin into fructose. The hydrolysis reaction was found to follow first order kinetics. Products containing 96 and 75% fructose were obtained upon hydrolysis respectively from inulin and extract.

  1. Production of Chiral (R)-3-Hydroxyoctanoic Acid Monomers, Catalyzed by Pseudomonas fluorescens GK13 Poly(3-Hydroxyoctanoic Acid) Depolymerase▿

    PubMed Central

    Gangoiti, Joana; Santos, Marta; Llama, María J.; Serra, Juan L.

    2010-01-01

    The extracellular medium-chain-length polyhydroxyalkanoate (MCL-PHA) depolymerase of Pseudomonas fluorescens GK13 catalyzes the hydrolysis of poly(3-hydroxyoctanoic acid) [P(3HO)]. Based on the strong tendency of the enzyme to interact with hydrophobic materials, a low-cost method which allows the rapid and easy purification and immobilization of the enzyme has been developed. Thus, the extracellular P(3HO) depolymerase present in the culture broth of cells of P. fluorescens GK13 grown on mineral medium supplemented with P(3HO) as the sole carbon and energy source has been tightly adsorbed onto a commercially available polypropylene support (Accurel MP-1000) with high yield and specificity. The activity of the pure enzyme was enhanced by the presence of detergents and organic solvents, and it was retained after treatment with an SDS-denaturing cocktail under both reducing and nonreducing conditions. The time course of the P(3HO) hydrolysis catalyzed by the soluble and immobilized enzyme has been assessed, and the resulting products have been identified. After 24 h of hydrolysis, the dimeric ester of 3-HO [(R)-3-HO-HO] was obtained as the main product of the soluble enzyme. However, the immobilized enzyme catalyzes almost the complete hydrolysis of P(3HO) polymer to (R)-3-HO monomers under the same conditions. PMID:20400568

  2. 7-deoxyloganetic acid synthase catalyzes a key 3 step oxidation to form 7-deoxyloganetic acid in Catharanthus roseus iridoid biosynthesis.

    PubMed

    Salim, Vonny; Wiens, Brent; Masada-Atsumi, Sayaka; Yu, Fang; De Luca, Vincenzo

    2014-05-01

    Iridoids are key intermediates required for the biosynthesis of monoterpenoid indole alkaloids (MIAs), as well as quinoline alkaloids. Although most iridoid biosynthetic genes have been identified, one remaining three step oxidation required to form the carboxyl group of 7-deoxyloganetic acid has yet to be characterized. Here, it is reported that virus-induced gene silencing of 7-deoxyloganetic acid synthase (7DLS, CYP76A26) in Catharanthus roseus greatly decreased levels of secologanin and the major MIAs, catharanthine and vindoline in silenced leaves. Functional expression of this gene in Saccharomyces cerevisiae confirmed its function as an authentic 7DLS that catalyzes the 3 step oxidation of iridodial-nepetalactol to form 7-deoxyloganetic acid. The identification of CYP76A26 removes a key bottleneck for expression of iridoid and related MIA pathways in various biological backgrounds.

  3. 7-deoxyloganetic acid synthase catalyzes a key 3 step oxidation to form 7-deoxyloganetic acid in Catharanthus roseus iridoid biosynthesis.

    PubMed

    Salim, Vonny; Wiens, Brent; Masada-Atsumi, Sayaka; Yu, Fang; De Luca, Vincenzo

    2014-05-01

    Iridoids are key intermediates required for the biosynthesis of monoterpenoid indole alkaloids (MIAs), as well as quinoline alkaloids. Although most iridoid biosynthetic genes have been identified, one remaining three step oxidation required to form the carboxyl group of 7-deoxyloganetic acid has yet to be characterized. Here, it is reported that virus-induced gene silencing of 7-deoxyloganetic acid synthase (7DLS, CYP76A26) in Catharanthus roseus greatly decreased levels of secologanin and the major MIAs, catharanthine and vindoline in silenced leaves. Functional expression of this gene in Saccharomyces cerevisiae confirmed its function as an authentic 7DLS that catalyzes the 3 step oxidation of iridodial-nepetalactol to form 7-deoxyloganetic acid. The identification of CYP76A26 removes a key bottleneck for expression of iridoid and related MIA pathways in various biological backgrounds. PMID:24594312

  4. Asymmetric synthesis of allylic sulfonic acids: enantio- and regioselective iridium-catalyzed allylations of Na2SO3.

    PubMed

    Liu, Wei; Zhao, Xiao-ming; Zhang, Hong-bo; Zhang, Liang; Zhao, Ming-zhu

    2014-12-15

    An enantioselective allylation reaction of allylic carbonates with sodium sulfite (Na2 SO3 ) catalyzed by Ir complex was accomplished, providing allylic sulfonic acids in good to excellent yields with a high level of enantio- and regioselectivities. (R)-2-Phenyl-2-sulfoacetic acid, a key intermediate for the synthesis of Cefsulodin and Sulbenicillin, was synthesized as well.

  5. Asymmetric synthesis of allylic sulfonic acids: enantio- and regioselective iridium-catalyzed allylations of Na2SO3.

    PubMed

    Liu, Wei; Zhao, Xiao-ming; Zhang, Hong-bo; Zhang, Liang; Zhao, Ming-zhu

    2014-12-15

    An enantioselective allylation reaction of allylic carbonates with sodium sulfite (Na2 SO3 ) catalyzed by Ir complex was accomplished, providing allylic sulfonic acids in good to excellent yields with a high level of enantio- and regioselectivities. (R)-2-Phenyl-2-sulfoacetic acid, a key intermediate for the synthesis of Cefsulodin and Sulbenicillin, was synthesized as well. PMID:25367779

  6. Modular Synthesis of Arylacetic Acid Esters, Thioesters, and Amides from Aryl Ethers via Rh(II)-Catalyzed Diazo Arylation.

    PubMed

    Best, Daniel; Jean, Mickaël; van de Weghe, Pierre

    2016-09-01

    One-pot formation of arylacetic acid esters, thioesters, and amides via Rh(II)-catalyzed arylation of a Meldrum's acid-derived diazo reagent with electron-rich arenes is described. The methodology was used to efficiently synthesize an anticancer compound. PMID:27465907

  7. Computational Study of Formic Acid Dehydrogenation Catalyzed by Al(III)-Bis(imino)pyridine.

    PubMed

    Lu, Qian-Qian; Yu, Hai-Zhu; Fu, Yao

    2016-03-18

    The mechanism of formic acid dehydrogenation catalyzed by the bis(imino)pyridine-ligated aluminum hydride complex (PDI(2-))Al(THF)H (PDI=bis(imino)pyridine) was studied by density functional theory calculations. The overall transformation is composed of two stages: catalyst activation and the catalytic cycle. The catalyst activation begins with O-H bond cleavage of HCOOH promoted by aluminum-ligand cooperation, followed by HCOOH-assisted Al-H bond cleavage, and protonation of the imine carbon atom of the bis(imino)pyridine ligand. The resultant doubly protonated complex ((H,H) PDI)Al(OOCH)3 is the active catalyst for formic acid dehydrogenation. Given this, the catalytic cycle includes β-hydride elimination of ((H,H) PDI)Al(OOCH)3 to produce CO2, and the formed ((H,H) PDI)Al(OOCH)2 H mediates HCOOH to release H2. PMID:26879469

  8. Evaluation of bicinchoninic acid as a ligand for copper(I)-catalyzed azide-alkyne bioconjugations.

    PubMed

    Christen, Erik H; Gübeli, Raphael J; Kaufmann, Beate; Merkel, Lars; Schoenmakers, Ronald; Budisa, Nediljko; Fussenegger, Martin; Weber, Wilfried; Wiltschi, Birgit

    2012-09-01

    The Cu(I)-catalyzed cycloaddition of terminal azides and alkynes (click chemistry) represents a highly specific reaction for the functionalization of biomolecules with chemical moieties such as dyes or polymer matrices. In this study we evaluate the use of bicinchoninic acid (BCA) as a ligand for Cu(I) under physiological reaction conditions. We demonstrate that the BCA-Cu(I)-complex represents an efficient catalyst for the conjugation of fluorophores or biotin to alkyne- or azide-functionalized proteins resulting in increased or at least equal reaction yields compared to commonly used catalysts like Cu(I) in complex with TBTA (tris[(1-benzyl-1H-1,2,3-triazol-4-yl)methyl]amine) or BPAA (bathophenanthroline disulfonic acid). The stabilization of Cu(I) with BCA represents a new strategy for achieving highly efficient bioconjugation reactions under physiological conditions in many application fields. PMID:22821135

  9. Mechanism of silver- and copper-catalyzed decarboxylation reactions of aryl carboxylic acids.

    PubMed

    Xue, Liqin; Su, Weiping; Lin, Zhenyang

    2011-11-28

    Silver- and copper-catalyzed decarboxylation reactions of aryl carboxylic acids were investigated with the aid of density functional theory calculations. The reaction mechanism starts with a carboxylate complex of silver or copper. Decarboxylation occurs via ejecting CO(2) from the carboxylate complex followed by protodemetallation with an aryl carboxylic acid molecule to regenerate the starting complex. Our results indicated that the primary factor to affect the overall reaction barriers is the ortho steric destabilization effect on the starting carboxylate complexes for most cases. Certain ortho substituents that are capable of coordinating with the catalyst metal center without causing significant ring strain stabilize the decarboxylation transition states and reduce the overall reaction barriers. However, the coordination effect is found to be the secondary factor when compared with the ortho effect. PMID:21979246

  10. Two step esterification-transesterification process of wet greasy sewage sludge for biodiesel production.

    PubMed

    Urrutia, C; Sangaletti-Gerhard, N; Cea, M; Suazo, A; Aliberti, A; Navia, R

    2016-01-01

    Sewage sludge generated in municipal wastewater treatment plants was used as a feedstock for biodiesel production via esterification/transesterification in a two-step process. In the first esterification step, greasy and secondary sludge were tested using acid and enzymatic catalysts. The results indicate that both catalysts performed the esterification of free fatty acids (FFA) simultaneously with the transesterification of triacylglycerols (TAG). Acid catalyst demonstrated better performance in FFA esterification compared to TAG transesterification, while enzymatic catalyst showed the ability to first hydrolyze TAG in FFA, which were esterified to methyl esters. In addition, FAME concentration using greasy sludge were higher (63.9% and 58.7%), compared with those of secondary sludge (11% and 16%), using acid and enzymatic catalysts, respectively. Therefore, only greasy sludge was used in the second step of alkaline transesterification. The alkaline transesterification of the previously esterified greasy sludge reached a maximum FAME concentration of 65.4% when using acid catalyst.

  11. Novel Enzyme Family Found in Filamentous Fungi Catalyzing trans-4-Hydroxylation of l-Pipecolic Acid

    PubMed Central

    Hibi, Makoto; Mori, Ryosuke; Miyake, Ryoma; Kawabata, Hiroshi; Kozono, Shoko; Takahashi, Satomi

    2016-01-01

    Hydroxypipecolic acids are bioactive compounds widely distributed in nature and are valuable building blocks for the organic synthesis of pharmaceuticals. We have found a novel hydroxylating enzyme with activity toward l-pipecolic acid (l-Pip) in a filamentous fungus, Fusarium oxysporum c8D. The enzyme l-Pip trans-4-hydroxylase (Pip4H) of F. oxysporum (FoPip4H) belongs to the Fe(II)/α-ketoglutarate-dependent dioxygenase superfamily, catalyzes the regio- and stereoselective hydroxylation of l-Pip, and produces optically pure trans-4-hydroxy-l-pipecolic acid (trans-4-l-HyPip). Amino acid sequence analysis revealed several fungal enzymes homologous with FoPip4H, and five of these also had l-Pip trans-4-hydroxylation activity. In particular, the homologous Pip4H enzyme derived from Aspergillus nidulans FGSC A4 (AnPip4H) had a broader substrate specificity spectrum than other homologues and reacted with the l and d forms of various cyclic and aliphatic amino acids. Using FoPip4H as a biocatalyst, a system for the preparative-scale production of chiral trans-4-l-HyPip was successfully developed. Thus, we report a fungal family of l-Pip hydroxylases and the enzymatic preparation of trans-4-l-HyPip, a bioactive compound and a constituent of secondary metabolites with useful physiological activities. PMID:26801577

  12. Investigation of emulsified, acid and acid-alkali catalyzed mesoporous bioactive glass microspheres for bone regeneration and drug delivery.

    PubMed

    Miao, Guohou; Chen, Xiaofeng; Dong, Hua; Fang, Liming; Mao, Cong; Li, Yuli; Li, Zhengmao; Hu, Qing

    2013-10-01

    Acid-catalyzed mesoporous bioactive glass microspheres (MBGMs-A) and acid-alkali co-catalyzed mesoporous bioactive glass microspheres (MBGMs-B) were successfully synthesized via combination of sol-gel and water-in-oil (W/O) micro-emulsion methods. The structural, morphological and textural properties of mesoporous bioactive glass microspheres (MBGMs) were characterized by various techniques. Results show that both MBGMs-A and MBGMs-B exhibit regularly spherical shape but with different internal porous structures, i.e., a dense microstructure for MBGMs-A and internally porous structure for MBGMs-B. (29)Si NMR data reveal that MGBMs have low polymerization degree of silica network. The in vitro bioactivity tests indicate that the apatite formation rate of MBGMs-B was faster than that of MBGMs-A after soaking in simulated body fluid (SBF) solution. Furthermore, the two kinds of MBGMs have similar storage capacity of alendronate (AL), and the release behaviors of AL could be controlled due to their unique porous structure. In conclusion, the microspheres are shown to be promising candidates as bone-related drug carriers and filling materials of composite scaffold for bone repair.

  13. Investigation of emulsified, acid and acid-alkali catalyzed mesoporous bioactive glass microspheres for bone regeneration and drug delivery.

    PubMed

    Miao, Guohou; Chen, Xiaofeng; Dong, Hua; Fang, Liming; Mao, Cong; Li, Yuli; Li, Zhengmao; Hu, Qing

    2013-10-01

    Acid-catalyzed mesoporous bioactive glass microspheres (MBGMs-A) and acid-alkali co-catalyzed mesoporous bioactive glass microspheres (MBGMs-B) were successfully synthesized via combination of sol-gel and water-in-oil (W/O) micro-emulsion methods. The structural, morphological and textural properties of mesoporous bioactive glass microspheres (MBGMs) were characterized by various techniques. Results show that both MBGMs-A and MBGMs-B exhibit regularly spherical shape but with different internal porous structures, i.e., a dense microstructure for MBGMs-A and internally porous structure for MBGMs-B. (29)Si NMR data reveal that MGBMs have low polymerization degree of silica network. The in vitro bioactivity tests indicate that the apatite formation rate of MBGMs-B was faster than that of MBGMs-A after soaking in simulated body fluid (SBF) solution. Furthermore, the two kinds of MBGMs have similar storage capacity of alendronate (AL), and the release behaviors of AL could be controlled due to their unique porous structure. In conclusion, the microspheres are shown to be promising candidates as bone-related drug carriers and filling materials of composite scaffold for bone repair. PMID:23910338

  14. 21 CFR 173.395 - Trifluoromethane sulfonic acid.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... levels not to exceed 0.2 percent of the reaction mixture to catalyze the directed esterification. (c) The esterification reaction is quenched with steam and water and the catalyst is removed with the aqueous...

  15. Unconventional Bifunctional Lewis-Brønsted Acid Activation Mode in Bicyclic Guanidine-Catalyzed Conjugate Addition Reactions.

    PubMed

    Cho, Bokun; Wong, Ming Wah

    2015-08-18

    DFT calculations have demonstrated that the unconventional bifunctional Brønsted-Lewis acid activation mode is generally applicable to a range of nucleophilic conjugate additions catalyzed by bicyclic guanidine catalysts. It competes readily with the conventional bifunctional Brønsted acid mode of activation. The optimal pro-nucleophiles for this unconventional bifunctional activation are acidic substrates with low pKa, while the best electrophiles are flexible 1,4-diamide and 1,4-diester conjugated systems.

  16. Laccase-catalyzed bisphenol A oxidation in the presence of 10-propyl sulfonic acid phenoxazine.

    PubMed

    Ivanec-Goranina, Rūta; Kulys, Juozas; Bachmatova, Irina; Marcinkevičienė, Liucija; Meškys, Rolandas

    2015-04-01

    The kinetics of the Coriolopsis byrsina laccase-catalyzed bisphenol A (BisA) oxidation was investigated in the absence and presence of electron-transfer mediator 3-phenoxazin-10-yl-propane-1-sulfonic acid (PPSA) at pH5.5 and 25°C. It was shown that oxidation rate of the hardly degrading compound BisA increased in the presence of the highly reactive substrate PPSA. The increase of reaction rate depends on PPSA and BisA concentrations as well on their ratio, e.g., at 0.2 mmol/L of BisA and 2 μmol/L of PPSA the rate increased 2 times. The kinetic data were analyzed using a scheme of synergistic laccase-catalyzed BisA oxidation. The calculated constant, characterizing reactivity of PPSA with laccase, is almost 1000 times higher than the constant, characterizing reactivity of BisA with laccase. This means that mediator-assisted BisA oxidation rate can be 1000 times higher in comparison to non-mediator reaction if compounds concentration is equal but very low.

  17. Oxidation of benzene with hydrogen peroxide catalyzed with ferrocene in the presence of pyrazine carboxylic acid

    NASA Astrophysics Data System (ADS)

    Shul'pina, L. S.; Durova, E. L.; Kozlov, Yu. N.; Kudinov, A. R.; Strelkova, T. V.; Shul'pin, G. B.

    2013-12-01

    It is found that ferrocene in the presence of small amounts of pyrazine carboxylic acid (PCA) effectively catalyzes the oxidation of benzene to phenol with hydrogen peroxide. Two main differences upon the oxidation of two different substrates, i.e., cyclohexane and benzene, with the same H2O2-ferrocene-PCA catalytic system are revealed: the rates of benzene oxidation and hydrogen peroxide decomposition are several times lower than the rate of cyclohexane oxidation at close concentrations of both substrates, and the rate constant ratios for the reactions of oxidizing particles with benzene and acetonitrile are significantly lower than would be expected for reactions involving free hydroxyl radicals. The overall rate of hydrogen peroxide decomposition, including both the catalase and oxidase routes, is lower in the presence of benzene than in the presence of cyclohexane. It is suggested on the grounds of these data that a catalytically active particle different from the one generated in the absence of benzene is formed in the presence of benzene. This particle catalyzes hydrogen peroxide decomposition less efficiently than the initial complex and generates a dissimilar oxidizing particle that exhibits higher selectivity. It is shown that reactivity of the system at higher concentrations of benzene differs from that of an initial system not containing an aromatic component with the capability of π-coordination with metal ions.

  18. Palladium-atom catalyzed formic acid decomposition and the switch of reaction mechanism with temperature.

    PubMed

    He, Nan; Li, Zhen Hua

    2016-04-21

    Formic acid decomposition (FAD) reaction has been an innovative way for hydrogen energy. Noble metal catalysts, especially palladium-containing nanoparticles, supported or unsupported, perform well in this reaction. Herein, we considered the simplest model, wherein one Pd atom is used as the FAD catalyst. With high-level theoretical calculations of CCSD(T)/CBS quality, we investigated all possible FAD pathways. The results show that FAD catalyzed by one Pd atom follows a different mechanism compared with that catalyzed by surfaces or larger clusters. At the initial stage of the reaction, FAD follows a dehydration route and is quickly poisoned by CO due to the formation of very stable PdCO. PdCO then becomes the actual catalyst for FAD at temperatures approximately below 1050 K. Beyond 1050 K, there is a switch of catalyst from PdCO to Pd atom. The results also show that dehydration is always favoured over dehydrogenation on either the Pd-atom or PdCO catalyst. On the Pd-atom catalyst, neither dehydrogenation nor dehydration follows the formate mechanism. In contrast, on the PdCO catalyst, dehydrogenation follows the formate mechanism, whereas dehydration does not. We also systematically investigated the performance of 24 density functional theory methods. We found that the performance of the double hybrid mPW2PLYP functional is the best, followed by the B3LYP, B3PW91, N12SX, M11, and B2PLYP functionals.

  19. Palladium-atom catalyzed formic acid decomposition and the switch of reaction mechanism with temperature.

    PubMed

    He, Nan; Li, Zhen Hua

    2016-04-21

    Formic acid decomposition (FAD) reaction has been an innovative way for hydrogen energy. Noble metal catalysts, especially palladium-containing nanoparticles, supported or unsupported, perform well in this reaction. Herein, we considered the simplest model, wherein one Pd atom is used as the FAD catalyst. With high-level theoretical calculations of CCSD(T)/CBS quality, we investigated all possible FAD pathways. The results show that FAD catalyzed by one Pd atom follows a different mechanism compared with that catalyzed by surfaces or larger clusters. At the initial stage of the reaction, FAD follows a dehydration route and is quickly poisoned by CO due to the formation of very stable PdCO. PdCO then becomes the actual catalyst for FAD at temperatures approximately below 1050 K. Beyond 1050 K, there is a switch of catalyst from PdCO to Pd atom. The results also show that dehydration is always favoured over dehydrogenation on either the Pd-atom or PdCO catalyst. On the Pd-atom catalyst, neither dehydrogenation nor dehydration follows the formate mechanism. In contrast, on the PdCO catalyst, dehydrogenation follows the formate mechanism, whereas dehydration does not. We also systematically investigated the performance of 24 density functional theory methods. We found that the performance of the double hybrid mPW2PLYP functional is the best, followed by the B3LYP, B3PW91, N12SX, M11, and B2PLYP functionals. PMID:27005983

  20. Production of alkyl esters from macaw palm oil by a sequential hydrolysis/esterification process using heterogeneous biocatalysts: optimization by response surface methodology.

    PubMed

    Bressani, Ana Paula P; Garcia, Karen C A; Hirata, Daniela B; Mendes, Adriano A

    2015-02-01

    The present study deals with the enzymatic synthesis of alkyl esters with emollient properties by a sequential hydrolysis/esterification process (hydroesterification) using unrefined macaw palm oil from pulp seeds (MPPO) as feedstock. Crude enzymatic extract from dormant castor bean seeds was used as biocatalyst in the production of free fatty acids (FFA) by hydrolysis of MPPO. Esterification of purified FFA with several alcohols in heptane medium was catalyzed by immobilized Thermomyces lanuginosus lipase (TLL) on poly-hydroxybutyrate (PHB) particles. Under optimal experimental conditions (mass ratio oil:buffer of 35% m/m, reaction temperature of 35 °C, biocatalyst concentration of 6% m/m, and stirring speed of 1,000 rpm), complete hydrolysis of MPPO was reached after 110 min of reaction. Maximum ester conversion percentage of 92.4 ± 0.4% was reached using hexanol as acyl acceptor at 750 mM of each reactant after 15 min of reaction. The biocatalyst retained full activity after eight successive cycles of esterification reaction. These results show that the proposed process is a promising strategy for the synthesis of alkyl esters of industrial interest from macaw palm oil, an attractive option for the Brazilian oleochemical industry.

  1. Highly chemoselective esterification reactions and Boc/THP/TBDMS discriminating deprotections under samarium(III) catalysis.

    PubMed

    Gopinath, Pushparathinam; Nilaya, Surapaneni; Muraleedharan, Kannoth Manheri

    2011-04-15

    The usefulness of SmCl(3) as an excellent catalyst for chemoselective esterifications and selective removal of acid sensitive protecting groups such as Boc, THP, and TBDMS in the presence of one another is demonstrated through suitable examples.

  2. Highly efficient chemical process to convert mucic acid into adipic acid and DFT studies of the mechanism of the rhenium-catalyzed deoxydehydration.

    PubMed

    Li, Xiukai; Wu, Di; Lu, Ting; Yi, Guangshun; Su, Haibin; Zhang, Yugen

    2014-04-14

    The production of bulk chemicals and fuels from renewable bio-based feedstocks is of significant importance for the sustainability of human society. Adipic acid, as one of the most-demanded drop-in chemicals from a bioresource, is used primarily for the large-volume production of nylon-6,6 polyamide. It is highly desirable to develop sustainable and environmentally friendly processes for the production of adipic acid from renewable feedstocks. However, currently there is no suitable bio-adipic acid synthesis process. Demonstrated herein is the highly efficient synthetic protocol for the conversion of mucic acid into adipic acid through the oxorhenium-complex-catalyzed deoxydehydration (DODH) reaction and subsequent Pt/C-catalyzed transfer hydrogenation. Quantitative yields (99 %) were achieved for the conversion of mucic acid into muconic acid and adipic acid either in separate sequences or in a one-step process.

  3. Acid-catalyzed hydrothermal severity on the fractionation of agricultural residues for xylose-rich hydrolyzates.

    PubMed

    Lee, Ji Ye; Ryu, Hyun Jin; Oh, Kyeong Keun

    2013-03-01

    The objective of this work was to investigate the feasibility of acid-catalyzed hydrothermal fractionation for maximum solubilization of the hemicellulosic portion of three agricultural residues. The fractionation conditions converted into combined severity factor (CS) in the range of 1.2-2.9. The highest hemicellulose yield of 87.88% was achieved when barley straw was fractionated at a CS of 2.19. However, the maximum glucose release of 15.29% was achieved for the case of rice straw. The maximum productions of various by-products were observed with the fractionation of rape straw: 0.88 g/L of 5-hydroxymethylfurfural (5-HMF), 2.16 g/L of furfural, 0.44 g/L of levulinic acid, 1.59 g/L of formic acid, and 3.06 g/L of acetic acid. The highest selectivities, a criterion for evaluating the fractionation of 21.55 for fractionated solid and 7.48 for liquid hydrolyzate were obtained from barley straw.

  4. Membrane protein complexes catalyze both 4- and 3-hydroxylation of cinnamic acid derivatives in monolignol biosynthesis.

    PubMed

    Chen, Hsi-Chuan; Li, Quanzi; Shuford, Christopher M; Liu, Jie; Muddiman, David C; Sederoff, Ronald R; Chiang, Vincent L

    2011-12-27

    The hydroxylation of 4- and 3-ring carbons of cinnamic acid derivatives during monolignol biosynthesis are key steps that determine the structure and properties of lignin. Individual enzymes have been thought to catalyze these reactions. In stem differentiating xylem (SDX) of Populus trichocarpa, two cinnamic acid 4-hydroxylases (PtrC4H1 and PtrC4H2) and a p-coumaroyl ester 3-hydroxylase (PtrC3H3) are the enzymes involved in these reactions. Here we present evidence that these hydroxylases interact, forming heterodimeric (PtrC4H1/C4H2, PtrC4H1/C3H3, and PtrC4H2/C3H3) and heterotrimeric (PtrC4H1/C4H2/C3H3) membrane protein complexes. Enzyme kinetics using yeast recombinant proteins demonstrated that the enzymatic efficiency (V(max)/k(m)) for any of the complexes is 70-6,500 times greater than that of the individual proteins. The highest increase in efficiency was found for the PtrC4H1/C4H2/C3H3-mediated p-coumaroyl ester 3-hydroxylation. Affinity purification-quantitative mass spectrometry, bimolecular fluorescence complementation, chemical cross-linking, and reciprocal coimmunoprecipitation provide further evidence for these multiprotein complexes. The activities of the recombinant and SDX plant proteins demonstrate two protein-complex-mediated 3-hydroxylation paths in monolignol biosynthesis in P. trichocarpa SDX; one converts p-coumaric acid to caffeic acid and the other converts p-coumaroyl shikimic acid to caffeoyl shikimic acid. Cinnamic acid 4-hydroxylation is also mediated by the same protein complexes. These results provide direct evidence for functional involvement of membrane protein complexes in monolignol biosynthesis.

  5. Kinetics of acid-catalyzed degradation of cyclosporin A and its analogs in aqueous solution.

    PubMed

    Oliyai, R; Safadi, M; Meier, P G; Hu, M K; Rich, D H; Stella, V J

    1994-03-01

    The kinetics and mechanism of the degradation of cyclosporin A have been studied under aqueous acidic conditions. The rate of degradation was found to be specific acid-catalyzed over the pH range studied (1-4), with isocyclosporin A as the predominant degradation product. Selective reduction of the olefinic bond of the amino acid 2-N-methyl-(R)-((E)-2-butenyl)-4-methyl-L-threonine (MeBmt) did not affect the overall degradation kinetics and product distribution of cyclosporin A. These observations indicate that the alternative degradation pathway involving intramolecular alkoxy addition to the olefinic bond of amino acid MeBmt apparently does not significantly contribute to the overall degradation kinetics of cyclosporin A in the pH range 1-4. The chemical reactivity of O-acetyl-cyclosporin A was examined to probe the governing mechanism for the isomerization of cyclosporin A. Under identical conditions, O-acetyl-cyclosporin A showed a much greater chemical stability than cyclosporin A, consistent with a mechanism involving the hydroxyoxazolidine intermediate. The chemical stability of cyclosporin C, which contains two beta-hydroxyl groups, was also examined. The rate and product distribution for the degradation of cyclosporin C suggest that under aqueous acidic conditions it undergoes N,O-acyl migration solely at the amino acid residue MeBmt. Additionally, the impact of side-chain bulkiness of amino acid MeBmt was examined by studying the degradation kinetics of a series of cyclosporin A analogs.(ABSTRACT TRUNCATED AT 250 WORDS)

  6. Acid-, base-, and lewis-acid-catalyzed heterolysis of methoxide from an alpha-hydroxy-beta-methoxy radical: models for reactions catalyzed by coenzyme B12-dependent diol dehydratase.

    PubMed

    Xu, Libin; Newcomb, Martin

    2005-11-11

    [Reaction: see text].A model for glycol radicals was employed in laser flash photolysis kinetic studies of catalysis of the fragmentation of a methoxy group adjacent to an alpha-hydroxy radical center. Photolysis of a phenylselenylmethylcyclopropane precursor gave a cyclopropylcarbinyl radical that rapidly ring opened to the target alpha-hydroxy-beta-methoxy radical (3). Heterolysis of the methoxy group in 3 gave an enolyl radical (4a) or an enol ether radical cation (4b), depending upon pH. Radicals 4 contain a 2,2-diphenylcyclopropane reporter group, and they rapidly opened to give UV-observable diphenylalkyl radicals as the final products. No heterolysis was observed for radical 3 under neutral conditions. In basic aqueous acetonitrile solutions, specific base catalysis of the heterolysis was observed; the pK(a) of radical 3 was determined to be 12.5 from kinetic titration plots, and the ketyl radical formed by deprotonation of 3 eliminated methoxide with a rate constant of 5 x 10(7) s(-1). In the presence of carboxylic acids in acetonitrile solutions, radical 3 eliminated methanol in a general acid-catalyzed reaction, and rate constants for protonation of the methoxy group in 3 by several acids were measured. Radical 3 also reacted by fragmentation of methoxide in Lewis-acid-catalyzed heterolysis reactions; ZnBr2, Sc(OTf)3, and BF3 were found to be efficient catalysts. Catalytic rate constants for the heterolysis reactions were in the range of 3 x 10(4) to 2 x 10(6) s(-1). The Lewis-acid-catalyzed heterolysis reactions are fast enough for kinetic competence in coenzyme B12 dependent enzyme-catalyzed reactions of glycols, and Lewis-acid-catalyzed cleavages of beta-ethers in radicals might be applied in synthetic reactions.

  7. An atom-economic approach to carboxylic acids via Pd-catalyzed direct addition of formic acid to olefins with acetic anhydride as a co-catalyst.

    PubMed

    Wang, Yang; Ren, Wenlong; Shi, Yian

    2015-08-21

    An effective Pd-catalyzed hydrocarboxylation of olefins using formic acid with acetic anhydride as a co-catalyst is described. A variety of carboxylic acids are obtained in good yields with high regioselectivities under mild reaction conditions without the use of toxic CO gas.

  8. Mechanisms and energetics for acid catalyzed β-D-glucose conversion to 5-hydroxymethylfurfurl.

    PubMed

    Qian, Xianghong

    2011-10-27

    Car-Parrinello based ab initio molecular dynamics (CPMD) coupled with metadynamics (MTD) simulations were carried out to investigate the mechanism and energetics for acid-catalyzed β-d-glucose conversion to 5-hydroxymethylfurfurl (HMF) in water. HMF is a critical intermediate for biomass conversion to biofuels. It was found that protonation of the C2-OH on glucose, the breakage of the C2-O2 bond, and the formation of the C2-O5 bond is the critical rate-limiting step for the direct glucose conversion to HMF without converting to fructose first, contrary to the wide-spread assumption in literature that fructose is the main intermediate for glucose conversion to HMF. The calculated reaction barrier of 30-35 kcal/mol appears to be solvent-induced and is in excellent agreement with experimental observations. PMID:21916465

  9. Efficient Acid-catalyzed 18F/19F Fluoride Exchange of BODIPY Dyes

    PubMed Central

    Keliher, Edmund J.; Klubnick, Jenna A.; Reiner, Thomas; Mazitschek, Ralph

    2014-01-01

    Fluorine containing fluorochromes represent important validation agents for PET imaging agents as they can be easily rapidly validated in cells by fluorescence imaging. In particular, the 18F-labeled BODIPY-FL fluorophore has emerged as an important platform but little is known about alternative 18F-labeling strategies or labeling on red shifted fluorophores. Here we explore the acid-catalyzed 18F/19F exchange on a range of commercially available N-hydroxysuccinimidyl ester and maleimide BODIPY fluorophores. We show this method to be a simple and efficient 18F-labeling strategy for a diverse span of fluorescent compounds, including a BODIPY modified PARP-1 inhibitor, and amine- and thiol-reactive BODIPY fluorophores. PMID:24596307

  10. Cinchona Urea-Catalyzed Asymmetric Sulfa-Michael Reactions: The Brønsted Acid-Hydrogen Bonding Model.

    PubMed

    Grayson, Matthew N; Houk, K N

    2016-07-27

    The cinchona alkaloid-derived urea-catalyzed asymmetric conjugate addition of aromatic thiols to cycloalkenones was studied using density functional theory (DFT). Deprotonation of the thiol gives a protonated amine that activates the electrophile by Brønsted acid catalysis, while the urea group binds the nucleophilic thiolate by hydrogen bonding. These results demonstrate the generality of the Brønsted acid-hydrogen bonding transition state (TS) model for cinchona alkaloid catalysis that we recently showed to be favored over Wynberg's widely accepted ion pair-hydrogen bonding model and represent the first detailed mechanistic study of a cinchona urea-catalyzed reaction. The conformation of the catalyst methoxy group has a strong effect on the TS, an effect overlooked in previous mechanistic studies of reactions catalyzed by cinchona alkaloids.

  11. Lipase-catalyzed synthesis of fatty acid amide (erucamide) using fatty acid and urea.

    PubMed

    Awasthi, Neeraj Praphulla; Singh, R P

    2007-01-01

    Ammonolysis of fatty acids to the corresponding fatty acid amides is efficiently catalysed by Candida antartica lipase (Novozym 435). In the present paper lipase-catalysed synthesis of erucamide by ammonolysis of erucic acid and urea in organic solvent medium was studied and optimal conditions for fatty amides synthesis were established. In this process erucic acid gave 88.74 % pure erucamide after 48 hour and 250 rpm at 60 degrees C with 1:4 molar ratio of erucic acid and urea, the organic solvent media is 50 ml tert-butyl alcohol (2-methyl-2-propanol). This process for synthesis is economical as we used urea in place of ammonia or other amidation reactant at atmospheric pressure. The amount of catalyst used is 3 %.

  12. Lipase-catalyzed synthesis of fatty acid amide (erucamide) using fatty acid and urea.

    PubMed

    Awasthi, Neeraj Praphulla; Singh, R P

    2007-01-01

    Ammonolysis of fatty acids to the corresponding fatty acid amides is efficiently catalysed by Candida antartica lipase (Novozym 435). In the present paper lipase-catalysed synthesis of erucamide by ammonolysis of erucic acid and urea in organic solvent medium was studied and optimal conditions for fatty amides synthesis were established. In this process erucic acid gave 88.74 % pure erucamide after 48 hour and 250 rpm at 60 degrees C with 1:4 molar ratio of erucic acid and urea, the organic solvent media is 50 ml tert-butyl alcohol (2-methyl-2-propanol). This process for synthesis is economical as we used urea in place of ammonia or other amidation reactant at atmospheric pressure. The amount of catalyst used is 3 %. PMID:17898456

  13. Mechanistic Investigation of Acid-Catalyzed Cleavage of Aryl-Ether Linkages: Implications for Lignin Depolymerization

    SciTech Connect

    Sturgeon, M. R.; Kim, S.; Chmely, S. C.; Foust, T. D.; Beckham, G. T.

    2013-01-01

    Carbon-oxygen bonds are the primary inter-monomer linkages lignin polymers in plant cell walls, and as such, catalyst development to cleave these linkages is of paramount importance to deconstruct biomass to its constituent monomers for the production of renewable fuels and chemicals. For many decades, acid catalysis has been used to depolymerize lignin. Lignin is a primary component of plant cell walls, which is connected primarily by aryl-ether linkages, and the mechanism of its deconstruction by acid is not well understood, likely due to its heterogeneous and complex nature compared to cellulose. For effective biomass conversion strategies, utilization of lignin is of significant relevance and as such understanding the mechanisms of catalytic lignin deconstruction to constituent monomers and oligomers is of keen interest. Here, we present a comprehensive experimental and theoretical study of the acid catalysis of a range of dimeric species exhibiting the b-O-4 linkage, the most common inter-monomer linkage in lignin. We demonstrate that the presence of a phenolic species dramatically increases the rate of cleavage in acid at 150 degrees C. Quantum mechanical calculations on dimers with the para-hydroxyl group demonstrate that this acid-catalyzed pathway differs from the nonphenolic dimmers. Importantly, this result implies that depolymerization of native lignin in the plant cell wall will proceed via an unzipping mechanism wherein b-O-4 linkages will be cleaved from the ends of the branched, polymer chains inwards toward the center of the polymer. To test this hypothesis further, we synthesized a homopolymer of b-O-4 with a phenolic hydroxyl group, and demonstrate that it is cleaved in acid from the end containing the phenolic hydroxyl group. This result suggests that genetic modifications to lignin biosynthesis pathways in plants that will enable lower severity processes to fractionate lignin for upgrading and for easier access to the carbohydrate fraction of

  14. Lewis Acid Catalyzed Regiospecific Cross-Dehydrative Coupling Reaction of 2-Furylcarbinols with β-Keto Amides or 4-Hydroxycoumarins: A Route to Furyl Enols.

    PubMed

    Miao, Maozhong; Luo, Yi; Li, Hongli; Xu, Xin; Chen, Zhengkai; Xu, Jianfeng; Ren, Hongjun

    2016-06-17

    Lewis acid catalyzed directly dehydrative carbon-carbon bond formation reaction of 2-furylcarbinols with β-keto amides provides a straightforward method for regioselective synthesis of (Z)-furyl enols. Moreover, this Lewis acid catalyzed cross-coupling reaction can be extended to an interesting heterocyclic version featuring a functionalized 3-furyl-4-hydroxycoumarin synthesis. PMID:27224045

  15. Acid-catalyzed conversion of xylose, xylan and straw into furfural by microwave-assisted reaction.

    PubMed

    Yemiş, Oktay; Mazza, Giuseppe

    2011-08-01

    Furfural is a biomass derived-chemical that can be used to replace petrochemicals. In this study, the acid-catalyzed conversion of xylose and xylan to furfural by microwave-assisted reaction was investigated at selected ranges of temperature (140-190°C), time (1-30 min), substrate concentration (1:5-1:200 solid:liquid ratio), and pH (2-0.13). We found that a temperature of 180°C, a solid:liquid ratio of 1:200, a residence time of 20 min, and a pH of 1.12 gave the best furfural yields. The effect of different Brønsted acids on the conversion efficiency of xylose and xylan was also evaluated, with hydrochloric acid being found to be the most effective catalyst. The microwave-assisted process provides highly efficient conversion: furfural yields obtained from wheat straw, triticale straw, and flax shives were 48.4%, 45.7%, and 72.1%, respectively. PMID:21620690

  16. A preliminary investigation of acid-catalyzed polymerization reactions of shale oil distillates

    SciTech Connect

    Netzel, D.A.

    1991-04-01

    Sinor (1989) reported that a major specialty market may exist for shale oil as an asphalt blending material. Shale oil can be converted to an asphalt blending material by acid catalyzed condensation and polymerization reactions of the many molecular species comprising the composition of shale oil. To simplify the investigation, crude shale oil was separated by distillation into three distillates of different hydrocarbon and heteroaromatic compositions. These distillates were then treated with two different types of acids to determine the effect of acid type on the end products. Three western shale oil distillates, a naphtha, a middle distillate, and an atmospheric gas oil, were reacted with anhydrous AlCl{sub 3} and 85% H{sub 2}SO{sub 4} under low-severity conditions. At relatively low temperatures, little change in the hydrocarbon composition was noted for the AlCl{sub 3} reactions. AlCl{sub 3}{center_dot} (a polymerized product and/or complex) was formed. However, it is assumed that the sludge was mainly the result of heteroaromatic-AlCl{sub 3} reactions.

  17. A preliminary investigation of acid-catalyzed polymerization reactions of shale oil distillates

    SciTech Connect

    Netzel, D.A.

    1991-04-01

    Sinor (1989) reported that a major specialty market may exist for shale oil as an asphalt blending material. Shale oil can be converted to an asphalt blending material by acid catalyzed condensation and polymerization reactions of the many molecular species comprising the composition of shale oil. To simplify the investigation, crude shale oil was separated by distillation into three distillates of different hydrocarbon and heteroaromatic compositions. These distillates were then treated with two different types of acids to determine the effect of acid type on the end products. Three western shale oil distillates, a naphtha, a middle distillate, and an atmospheric gas oil, were reacted with anhydrous AlCl{sub 3} and 85% H{sub 2}SO{sub 4} under low-severity conditions. At relatively low temperatures, little change in the hydrocarbon composition was noted for the AlCl{sub 3} reactions. AlCl{sub 3}{center dot} (a polymerized product and/or complex) was formed. However, it is assumed that the sludge was mainly the result of heteroaromatic-AlCl{sub 3} reactions.

  18. Selective Nickel- and Manganese-Catalyzed Decarboxylative Cross Coupling of Some α,β-Unsaturated Carboxylic Acids with Cyclic Ethers

    PubMed Central

    Zhang, Jia-Xiang; Wang, Yan-Jing; Zhang, Wei; Wang, Nai-Xing; Bai, Cui-Bing; Xing, Ya-Lan; Li, Yi-He; Wen, Jia-Long

    2014-01-01

    A nickel- and manganese-catalyzed decarboxylative cross coupling of α, β-unsaturated carboxylic acids with cyclic ethers such as tetrahydrofuran and 1, 4-dioxane was developed. Oxyalkylation was achieved when nickel acetate was used as catalyst, while manganese acetate promoted the reaction of alkenylation. PMID:25502282

  19. Combining enzymatic esterification with conventional alkaline transesterification in an integrated biodiesel process.

    PubMed

    Brask, Jesper; Damstrup, Marianne Linde; Nielsen, Per Munk; Holm, Hans Christian; Maes, Jeroen; De Greyt, Wim

    2011-04-01

    An integrated biodiesel process that combines enzymatic esterification and alkaline transesterification is suggested. With focus on the enzymatic step, the paper provides proof of concept and suggestions for further process development. Hence, palm fatty acid distillate (PFAD) has been enzymatically converted to fatty acid methyl esters in a two-step process using the immobilized lipase Novozym 435 in packed-bed columns. With only a small excess of methanol, the first reaction stage could reduce the free fatty acid (FFA) content from 85% to 5%. After removal of water by simple phase separation, it was possible to lower the FFA content to 2.5% in a second reaction stage. Both reaction stages are relatively fast with suggested reaction times of 15 min in column 1 (productivity 10 kg/kg/h) and 30 min in column 2 (productivity 5 kg/kg/h), resulting in 15% FFA after column 1 and 5% FFA after column 2. A lifetime study indicated that approximately 3,500 kg PFAD/kg Novozym 435 can be treated in the first reaction stage before the enzyme has become fully inactivated. With further optimization, the enzymatic process could be a real alternative to today's sulfuric acid catalyzed process. PMID:20878260

  20. Combining enzymatic esterification with conventional alkaline transesterification in an integrated biodiesel process.

    PubMed

    Brask, Jesper; Damstrup, Marianne Linde; Nielsen, Per Munk; Holm, Hans Christian; Maes, Jeroen; De Greyt, Wim

    2011-04-01

    An integrated biodiesel process that combines enzymatic esterification and alkaline transesterification is suggested. With focus on the enzymatic step, the paper provides proof of concept and suggestions for further process development. Hence, palm fatty acid distillate (PFAD) has been enzymatically converted to fatty acid methyl esters in a two-step process using the immobilized lipase Novozym 435 in packed-bed columns. With only a small excess of methanol, the first reaction stage could reduce the free fatty acid (FFA) content from 85% to 5%. After removal of water by simple phase separation, it was possible to lower the FFA content to 2.5% in a second reaction stage. Both reaction stages are relatively fast with suggested reaction times of 15 min in column 1 (productivity 10 kg/kg/h) and 30 min in column 2 (productivity 5 kg/kg/h), resulting in 15% FFA after column 1 and 5% FFA after column 2. A lifetime study indicated that approximately 3,500 kg PFAD/kg Novozym 435 can be treated in the first reaction stage before the enzyme has become fully inactivated. With further optimization, the enzymatic process could be a real alternative to today's sulfuric acid catalyzed process.

  1. Potential of phosphoric acid-catalyzed pretreatment and subsequent enzymatic hydrolysis for biosugar production from Gracilaria verrucosa.

    PubMed

    Kwon, Oh-Min; Kim, Sung-Koo; Jeong, Gwi-Taek

    2016-07-01

    This study combined phosphoric acid-catalyzed pretreatment and enzymatic hydrolysis to produce biosugars from Gracilaria verrucosa as a potential renewable resource for bioenergy applications. We optimized phosphoric acid-catalyzed pretreatment conditions to 1:10 solid-to-liquid ratio, 1.5 % phosphoric acid, 140 °C, and 60 min reaction time, producing a 32.52 ± 0.06 % total reducing sugar (TRS) yield. By subsequent enzymatic hydrolysis, a 68.61 ± 0.90 % TRS yield was achieved. These results demonstrate the potential of phosphoric acid to produce biosugars for biofuel and biochemical production applications. PMID:27003825

  2. Potential of phosphoric acid-catalyzed pretreatment and subsequent enzymatic hydrolysis for biosugar production from Gracilaria verrucosa.

    PubMed

    Kwon, Oh-Min; Kim, Sung-Koo; Jeong, Gwi-Taek

    2016-07-01

    This study combined phosphoric acid-catalyzed pretreatment and enzymatic hydrolysis to produce biosugars from Gracilaria verrucosa as a potential renewable resource for bioenergy applications. We optimized phosphoric acid-catalyzed pretreatment conditions to 1:10 solid-to-liquid ratio, 1.5 % phosphoric acid, 140 °C, and 60 min reaction time, producing a 32.52 ± 0.06 % total reducing sugar (TRS) yield. By subsequent enzymatic hydrolysis, a 68.61 ± 0.90 % TRS yield was achieved. These results demonstrate the potential of phosphoric acid to produce biosugars for biofuel and biochemical production applications.

  3. Sequential aldol condensation-transition metal-catalyzed addition reactions of aldehydes, methyl ketones, and arylboronic acids.

    PubMed

    Liao, Yuan-Xi; Xing, Chun-Hui; Israel, Matthew; Hu, Qiao-Sheng

    2011-04-15

    Sequential aldol condensation of aldehydes with methyl ketones followed by transition metal-catalyzed addition reactions of arylboronic acids to form β-substituted ketones is described. By using the 1,1'-spirobiindane-7,7'-diol (SPINOL)-based phosphite, an asymmetric version of this type of sequential reaction, with up to 92% ee, was also realized. Our study provided an efficient method to access β-substituted ketones and might lead to the development of other sequential/tandem reactions with transition metal-catalyzed addition reactions as the key step.

  4. Rh(III)-catalyzed decarboxylative ortho-heteroarylation of aromatic carboxylic acids by using the carboxylic acid as a traceless directing group.

    PubMed

    Qin, Xurong; Sun, Denan; You, Qiulin; Cheng, Yangyang; Lan, Jingbo; You, Jingsong

    2015-04-01

    Highly selective decarboxylative ortho-heteroarylation of aromatic carboxylic acids with various heteroarenes has been developed through Rh(III)-catalyzed two-fold C-H activation, which exhibits a wide substrate scope of both aromatic carboxylic acids and heteroarenes. The use of naturally occurring carboxylic acid as the directing group avoids troublesome extra steps for installation and removal of an external directing group.

  5. Application of palladium-catalyzed carboxyl anhydride-boronic acid cross coupling in the synthesis of novel bile acids analogs with modified side chains.

    PubMed

    Mayorquín-Torres, Martha C; Flores-Álamo, Marcos; Iglesias-Arteaga, Martin A

    2015-09-01

    Palladium-catalyzed cross coupling of 4-methoxycarbonyl phenyboronic acid with acetylated bile acids in which the carboxyl functions was activated by formation of a mixed anhydride with pivalic anhydride afforded the cross coupled compounds, which were converted in novel side chain modified bile acids by one pot carbonyl reduction/removal of the protecting acetyl groups by Wolff-Kishner reduction. Unambiguous assignments of the NMR signals and crystal characterization of the heretofore unknown compounds are provided.

  6. Computational Mechanistic Studies of Acid-Catalyzed Lignin Model Dimers for Lignin Depolymerization

    SciTech Connect

    Kim, S.; Sturgeon, M. R.; Chmely, S. C.; Paton, R. S.; Beckham, G. T.

    2013-01-01

    Lignin is a heterogeneous alkyl-aromatic polymer that constitutes up to 30% of plant cell walls, and is used for water transport, structure, and defense. The highly irregular and heterogeneous structure of lignin presents a major obstacle in the development of strategies for its deconstruction and upgrading. Here we present mechanistic studies of the acid-catalyzed cleavage of lignin aryl-ether linkages, combining both experimental studies and quantum chemical calculations. Quantum mechanical calculations provide a detailed interpretation of reaction mechanisms including possible intermediates and transition states. Solvent effects on the hydrolysis reactions were incorporated through the use of a conductor-like polarizable continuum model (CPCM) and with cluster models including explicit water molecules in the first solvation shell. Reaction pathways were computed for four lignin model dimers including 2-phenoxy-phenylethanol (PPE), 1-(para-hydroxyphenyl)-2-phenoxy-ethanol (HPPE), 2-phenoxy-phenyl-1,3-propanediol (PPPD), and 1-(para-hydroxyphenyl)-2-phenoxy-1,3-propanediol (HPPPD). Lignin model dimers with a para-hydroxyphenyl ether (HPPE and HPPPD) show substantial differences in reactivity relative to the phenyl ether compound (PPE and PPPD) which have been clarified theoretically and experimentally. The significance of these results for acid deconstruction of lignin in plant cell walls will be discussed.

  7. Dual Lewis Acid/Lewis Base Catalyzed Acylcyanation of Aldehydes: A Mechanistic Study.

    PubMed

    Laurell Nash, Anna; Hertzberg, Robin; Wen, Ye-Qian; Dahlgren, Björn; Brinck, Tore; Moberg, Christina

    2016-03-01

    A mechanistic investigation, which included a Hammett correlation analysis, evaluation of the effect of variation of catalyst composition, and low-temperature NMR spectroscopy studies, of the Lewis acid-Lewis base catalyzed addition of acetyl cyanide to prochiral aldehydes provides support for a reaction route that involves Lewis base activation of the acyl cyanide with formation of a potent acylating agent and cyanide ion. The cyanide ion adds to the carbonyl group of the Lewis acid activated aldehyde. O-Acylation by the acylated Lewis base to form the final cyanohydrin ester occurs prior to decomplexation from titanium. For less reactive aldehydes, the addition of cyanide is the rate-determining step, whereas, for more reactive, electron-deficient aldehydes, cyanide addition is rapid and reversible and is followed by rate-limiting acylation. The resting state of the catalyst lies outside the catalytic cycle and is believed to be a monomeric titanium complex with two alcoholate ligands, which only slowly converts into the product.

  8. Hetropolyacid-Catalyzed Oxidation of Glycerol into Lactic Acid under Mild Base-Free Conditions.

    PubMed

    Tao, Meilin; Yi, Xiaohu; Delidovich, Irina; Palkovits, Regina; Shi, Junyou; Wang, Xiaohong

    2015-12-21

    Lactic acid (LA) is a versatile platform molecule owing to the opportunity to transform this compound into useful chemicals and materials. Therefore, efficient production of LA based on inexpensive renewable feedstocks is of utmost importance for insuring its market availability. Herein, we report the efficient conversion of glycerol into LA catalyzed by heteropolyacids (HPAs) under mild base-free conditions. The catalytic performance of molecular HPAs appears to correlate with their redox potential and Brønsted acidity. Namely, H3 PMo(12)O(40) (HPMo) exhibits the best selectivity towards LA (90 %) with 88 % conversion of glycerol. Loading of HPMo onto a carbon support (HPMo/C) further improves LA productivity resulting in 94 % selectivity at 98 % conversion under optimized reaction conditions. The reaction takes place through the formation of dihydroxyacetone/glyceraldehyde and pyruvaldehyde as intermediates. No leaching of HPMo was observed under the applied reaction conditions and HPMo/C could be recycled 5 times without significant loss of activity.

  9. Mechanistic insights into a BINOL-derived phosphoric acid-catalyzed asymmetric Pictet-Spengler reaction.

    PubMed

    Overvoorde, Lois M; Grayson, Matthew N; Luo, Yi; Goodman, Jonathan M

    2015-03-01

    The reaction of tryptamine and (2-oxocyclohexyl)acetic acid can be catalyzed by 3,3'-bis(triphenylsilyl)-1,1'-bi-2-naphthol phosphoric acid to give an asymmetric β-carboline. This reaction was first studied by Holloway et al. ( Org. Lett. 2010 , 12 , 4720 - 4723 ), but their mechanistic work did not explain the high stereoselectivity achieved. This study uses density functional theory and hybrid quantum mechanics/molecular mechanics calculations to investigate this reaction and provide a model to explain its outcome. The step leading to diastereo- and enantioselectivity is an asymmetric Pictet-Spengler reaction involving an N-acyliminium ion bound to the catalyst in a bidentate fashion. This interaction occurs via hydrogen bonds between the two terminal oxygen atoms of the catalyst phosphate group and the hydrogen atoms at N and C2 of the substrate indole group. These bonds hold the transition structure rigidly and thus allow the catalyst triphenylsilyl groups to influence the enantioselectivity. PMID:25654215

  10. Glycolic acid-catalyzed deamidation of asparagine residues in degrading PLGA matrices: a computational study.

    PubMed

    Manabe, Noriyoshi; Kirikoshi, Ryota; Takahashi, Ohgi

    2015-03-31

    Poly(lactic-co-glycolic acid) (PLGA) is a strong candidate for being a drug carrier in drug delivery systems because of its biocompatibility and biodegradability. However, in degrading PLGA matrices, the encapsulated peptide and protein drugs can undergo various degradation reactions, including deamidation at asparagine (Asn) residues to give a succinimide species, which may affect their potency and/or safety. Here, we show computationally that glycolic acid (GA) in its undissociated form, which can exist in high concentration in degrading PLGA matrices, can catalyze the succinimide formation from Asn residues by acting as a proton-transfer mediator. A two-step mechanism was studied by quantum-chemical calculations using Ace-Asn-Nme (Ace = acetyl, Nme = NHCH3) as a model compound. The first step is cyclization (intramolecular addition) to form a tetrahedral intermediate, and the second step is elimination of ammonia from the intermediate. Both steps involve an extensive bond reorganization mediated by a GA molecule, and the first step was predicted to be rate-determining. The present findings are expected to be useful in the design of more effective and safe PLGA devices.

  11. Activation Energies for an Enzyme-Catalyzed and Acid-Catalyzed Hydrolysis: An Introductory Interdisciplinary Experiment for Chemists and Biochemists.

    ERIC Educational Resources Information Center

    Adams, K. R.; Meyers, M. B.

    1985-01-01

    Background information, procedures used, and typical results obtained are provided for an experiment in which students determine and compare the Arrhenius activation energies (Ea) for the hydrolysis of salicin. This reaction is subject to catalysis both by acid and by the enzyme emulsin (beta-d-glucoside glycohydrolase). (JN)

  12. Kinetics of Acid-Catalyzed Dehydration of Cyclic Hemiacetals in Organic Aerosol Particles in Equilibrium with Nitric Acid Vapor.

    PubMed

    Ranney, April P; Ziemann, Paul J

    2016-04-28

    Previous studies have shown that 1,4-hydroxycarbonyls, which are often major products of the atmospheric oxidation of hydrocarbons, can undergo acid-catalyzed cyclization and dehydration in aerosol particles to form highly reactive unsaturated dihydrofurans. In this study the kinetics of dehydration of cyclic hemiacetals, the rate-limiting step in this process, was investigated in a series of environmental chamber experiments in which secondary organic aerosol (SOA) containing cyclic hemiacetals was formed from the reaction of n-pentadecane with OH radicals in dry air in the presence of HNO3. A particle beam mass spectrometer was used to monitor the formation and dehydration of cyclic hemiacetals in real time, and SOA and HNO3 were quantified in filter samples by gravimetric analysis and ion chromatography. Measured dehydration rate constants increased linearly with increasing concentration of HNO3 in the gas phase and in SOA, corresponding to catalytic rate constants of 0.27 h(-1) ppmv(-1) and 7.0 h(-1) M(-1), respectively. The measured Henry's law constant for partitioning of HNO3 into SOA was 3.7 × 10(4) M atm(-1), ∼25% of the value for dissolution into water, and the acid dissociation constant was estimated to be <8 × 10(-4), at least a factor of 10(4) less than that for HNO3 in water. The results indicate that HNO3 was only weakly dissociated in the SOA and that dehydration of cyclic hemiacetals was catalyzed by molecular HNO3 rather than by H(+). The Henry's law constant and kinetics relationships measured here can be used to improve mechanisms and models of SOA formation from the oxidation of hydrocarbons in dry air in the presence of NOx, which are conditions commonly used in laboratory studies. The fate of cyclic hemiacetals in the atmosphere, where the effects of higher relative humidity, organic/aqueous phase separation, and acid catalysis by molecular H2SO4 and/or H(+) are likely to be important, is discussed. PMID:27043733

  13. Kinetics of Acid-Catalyzed Dehydration of Cyclic Hemiacetals in Organic Aerosol Particles in Equilibrium with Nitric Acid Vapor.

    PubMed

    Ranney, April P; Ziemann, Paul J

    2016-04-28

    Previous studies have shown that 1,4-hydroxycarbonyls, which are often major products of the atmospheric oxidation of hydrocarbons, can undergo acid-catalyzed cyclization and dehydration in aerosol particles to form highly reactive unsaturated dihydrofurans. In this study the kinetics of dehydration of cyclic hemiacetals, the rate-limiting step in this process, was investigated in a series of environmental chamber experiments in which secondary organic aerosol (SOA) containing cyclic hemiacetals was formed from the reaction of n-pentadecane with OH radicals in dry air in the presence of HNO3. A particle beam mass spectrometer was used to monitor the formation and dehydration of cyclic hemiacetals in real time, and SOA and HNO3 were quantified in filter samples by gravimetric analysis and ion chromatography. Measured dehydration rate constants increased linearly with increasing concentration of HNO3 in the gas phase and in SOA, corresponding to catalytic rate constants of 0.27 h(-1) ppmv(-1) and 7.0 h(-1) M(-1), respectively. The measured Henry's law constant for partitioning of HNO3 into SOA was 3.7 × 10(4) M atm(-1), ∼25% of the value for dissolution into water, and the acid dissociation constant was estimated to be <8 × 10(-4), at least a factor of 10(4) less than that for HNO3 in water. The results indicate that HNO3 was only weakly dissociated in the SOA and that dehydration of cyclic hemiacetals was catalyzed by molecular HNO3 rather than by H(+). The Henry's law constant and kinetics relationships measured here can be used to improve mechanisms and models of SOA formation from the oxidation of hydrocarbons in dry air in the presence of NOx, which are conditions commonly used in laboratory studies. The fate of cyclic hemiacetals in the atmosphere, where the effects of higher relative humidity, organic/aqueous phase separation, and acid catalysis by molecular H2SO4 and/or H(+) are likely to be important, is discussed.

  14. Lewis acid promoted ruthenium(II)-catalyzed etherifications by selective hydrogenation of carboxylic acids/esters.

    PubMed

    Li, Yuehui; Topf, Christoph; Cui, Xinjiang; Junge, Kathrin; Beller, Matthias

    2015-04-20

    Ethers are of fundamental importance in organic chemistry and they are an integral part of valuable flavors, fragrances, and numerous bioactive compounds. In general, the reduction of esters constitutes the most straightforward preparation of ethers. Unfortunately, this transformation requires large amounts of metal hydrides. Presented herein is a bifunctional catalyst system, consisting of Ru/phosphine complex and aluminum triflate, which allows selective synthesis of ethers by hydrogenation of esters or carboxylic acids. Different lactones were reduced in good yields to the desired products. Even challenging aromatic and aliphatic esters were reduced to the desired products. Notably, the in situ formed catalyst can be reused several times without any significant loss of activity.

  15. Lewis acid promoted ruthenium(II)-catalyzed etherifications by selective hydrogenation of carboxylic acids/esters.

    PubMed

    Li, Yuehui; Topf, Christoph; Cui, Xinjiang; Junge, Kathrin; Beller, Matthias

    2015-04-20

    Ethers are of fundamental importance in organic chemistry and they are an integral part of valuable flavors, fragrances, and numerous bioactive compounds. In general, the reduction of esters constitutes the most straightforward preparation of ethers. Unfortunately, this transformation requires large amounts of metal hydrides. Presented herein is a bifunctional catalyst system, consisting of Ru/phosphine complex and aluminum triflate, which allows selective synthesis of ethers by hydrogenation of esters or carboxylic acids. Different lactones were reduced in good yields to the desired products. Even challenging aromatic and aliphatic esters were reduced to the desired products. Notably, the in situ formed catalyst can be reused several times without any significant loss of activity. PMID:25728921

  16. Lipase-catalyzed reactions at interfaces of two-phase systems and microemulsions.

    PubMed

    Reis, P; Miller, R; Leser, M; Watzke, H

    2009-09-01

    This work describes the influence of two polar lipids, Sn-1/3 and Sn-2 monopalmitin, on the activity of lipase in biphasic systems and in microemulsions. In previous communications, we have shown that Sn-2 monoglycerides can replace Sn-1,3 regiospecific lipases at the oil-water interface, causing a drastically reduced rate of lipolysis. We here demonstrate that even if the lipase is expelled from the interface, it can catalyze esterification of the Sn-2 monoglyceride with fatty acids in both macroscopic oil-water systems and in microemulsions, leading to formation of di- and triglycerides. PMID:18795240

  17. Group Exchange between Ketones and Carboxylic Acids through Directing Group Assisted Rh-Catalyzed Reorganization of Carbon Skeletons.

    PubMed

    Lei, Zhi-Quan; Pan, Fei; Li, Hu; Li, Yang; Zhang, Xi-Sha; Chen, Kang; Wang, Xin; Li, Yu-Xue; Sun, Jian; Shi, Zhang-Jie

    2015-04-22

    The Rh(I)-catalyzed direct reorganization of organic frameworks and group exchanges between carboxylic acids and aryl ketones was developed with the assistance of directing group. Biaryls, alkenylarenes, and alkylarenes were produced in high efficiency from aryl ketones and the corresponding carboxylic acids by releasing the other molecule of carboxylic acids and carbon monoxide. A wide range of functional groups were well compatible. The exchanges between two partners were proposed to take place on the Rh-(III) center of key intermediates, supported by experimental mechanistic studies and computational calculations. The transformation unveiled the new catalytic pathway of the group transfer of two organic molecules.

  18. Group Exchange between Ketones and Carboxylic Acids through Directing Group Assisted Rh-Catalyzed Reorganization of Carbon Skeletons.

    PubMed

    Lei, Zhi-Quan; Pan, Fei; Li, Hu; Li, Yang; Zhang, Xi-Sha; Chen, Kang; Wang, Xin; Li, Yu-Xue; Sun, Jian; Shi, Zhang-Jie

    2015-04-22

    The Rh(I)-catalyzed direct reorganization of organic frameworks and group exchanges between carboxylic acids and aryl ketones was developed with the assistance of directing group. Biaryls, alkenylarenes, and alkylarenes were produced in high efficiency from aryl ketones and the corresponding carboxylic acids by releasing the other molecule of carboxylic acids and carbon monoxide. A wide range of functional groups were well compatible. The exchanges between two partners were proposed to take place on the Rh-(III) center of key intermediates, supported by experimental mechanistic studies and computational calculations. The transformation unveiled the new catalytic pathway of the group transfer of two organic molecules. PMID:25843169

  19. Three competitive transition states at the glycosidic bond of sucrose in its acid-catalyzed hydrolysis.

    PubMed

    Yamabe, Shinichi; Guan, Wei; Sakaki, Shigeyoshi

    2013-03-15

    The acid-catalyzed hydrolysis of sucrose to glucose and fructose was investigated by DFT calculations. Protonations to three ether oxygen atoms of the sucrose molecule, A, B, and (C, D), were compared. Three (B, the fructosyl-ring oxygen protonation; C, protonation to the bridge oxygen of the glycosidic bond for the glucosyl-oxygen cleavage; and D, protonation to that for the fructosyl-oxygen cleavage) gave the fragmentation. Paths B, C, and D were examined by the use of the sucrose molecule and H3O(+)(H2O)13. The path B needs a large activation energy, indicating that it is unlikely. The fragmentation transition state (TS1) of path C needs almost the same activation energy as that of path D. The isomerization TS of Int(C) → Int(D), TS(C → D), was also obtained as a bypass route. The present calculations showed that the path via the fructosyl-oxygen cleavage (D) is slightly (not absolutely) more favorable than that via the glucosyl-oxygen cleavage (C). PMID:23373870

  20. Investigation of the complex reaction coordinate of acid catalyzed amide hydrolysis from molecular dynamics simulations

    NASA Astrophysics Data System (ADS)

    Zahn, Dirk

    2004-05-01

    The rate-determining step of acid catalyzed peptide hydrolysis is the nucleophilic attack of a water molecule to the carbon atom of the amide group. Therein the addition of the hydroxyl group to the amide carbon atom involves the association of a water molecule transferring one of its protons to an adjacent water molecule. The protonation of the amide nitrogen atom follows as a separate reaction step. Since the nucleophilic attack involves the breaking and formation of several bonds, the underlying reaction coordinate is rather complex. We investigate this reaction step from path sampling Car-Parrinello molecular dynamics simulations. This approach does not require the predefinition of reaction coordinates and is thus particularly suited for investigating reaction mechanisms. From our simulations the most relevant components of the reaction coordinate are elaborated. Though the C⋯O distance of the oxygen atom of the water molecule performing the nucleophilic attack and the corresponding amide carbon atom is a descriptor of the reaction progress, a complete picture of the reaction coordinate must include all three molecules taking part in the reaction. Moreover, the proton transfer is found to depend on favorable solvent configurations. Thus, also the arrangement of non-reacting, i.e. solvent water molecules needs to be considered in the reaction coordinate.

  1. Production of Diethyl Terephthalate from Biomass-Derived Muconic Acid.

    PubMed

    Lu, Rui; Lu, Fang; Chen, Jiazhi; Yu, Weiqiang; Huang, Qianqian; Zhang, Junjie; Xu, Jie

    2016-01-01

    We report a cascade synthetic route to directly obtain diethyl terephthalate, a replacement for terephthalic acid, from biomass-derived muconic acid, ethanol, and ethylene. The process involves two steps: First, a substituted cyclohexene system is built through esterification and Diels-Alder reaction; then, a dehydrogenation reaction provides diethyl terephthalate. The key esterification reaction leads to improved solubility and modulates the electronic properties of muconic acid, thus promoting the Diels-Alder reaction with ethylene. With silicotungstic acid as the catalyst, nearly 100% conversion of muconic acid was achieved, and the cycloadducts were formed with more than 99.0% selectivity. The palladium-catalyzed dehydrogenation reaction preferentially occurs under neutral or mildly basic conditions. The total yield of diethyl terephthalate reached 80.6% based on the amount of muconic acid used in the two-step synthetic process. PMID:26592149

  2. The cytosolic carboxypeptidases CCP2 and CCP3 catalyze posttranslational removal of acidic amino acids

    PubMed Central

    Tort, Olivia; Tanco, Sebastián; Rocha, Cecilia; Bièche, Ivan; Seixas, Cecilia; Bosc, Christophe; Andrieux, Annie; Moutin, Marie-Jo; Avilés, Francesc Xavier; Lorenzo, Julia; Janke, Carsten

    2014-01-01

    The posttranslational modification of carboxy-terminal tails of tubulin plays an important role in the regulation of the microtubule cytoskeleton. Enzymes responsible for deglutamylating tubulin have been discovered within a novel family of mammalian cytosolic carboxypeptidases. The discovery of these enzymes also revealed the existence of a range of other substrates that are enzymatically deglutamylated. Only four of six mammalian cytosolic carboxypeptidases had been enzymatically characterized. Here we complete the functional characterization of this protein family by demonstrating that CCP2 and CCP3 are deglutamylases, with CCP3 being able to hydrolyze aspartic acids with similar efficiency. Deaspartylation is a novel posttranslational modification that could, in conjunction with deglutamylation, broaden the range of potential substrates that undergo carboxy-terminal processing. In addition, we show that CCP2 and CCP3 are highly regulated proteins confined to ciliated tissues. The characterization of two novel enzymes for carboxy-terminal protein modification provides novel insights into the broadness of this barely studied process. PMID:25103237

  3. A heteromeric membrane-bound prenyltransferase complex from hop catalyzes three sequential aromatic prenylations in the bitter acid pathway.

    PubMed

    Li, Haoxun; Ban, Zhaonan; Qin, Hao; Ma, Liya; King, Andrew J; Wang, Guodong

    2015-03-01

    Bitter acids (α and β types) account for more than 30% of the fresh weight of hop (Humulus lupulus) glandular trichomes and are well known for their contribution to the bitter taste of beer. These multiprenylated chemicals also show diverse biological activities, some of which have potential benefits to human health. The bitter acid biosynthetic pathway has been investigated extensively, and the genes for the early steps of bitter acid synthesis have been cloned and functionally characterized. However, little is known about the enzyme(s) that catalyze three sequential prenylation steps in the β-bitter acid pathway. Here, we employed a yeast (Saccharomyces cerevisiae) system for the functional identification of aromatic prenyltransferase (PT) genes. Two PT genes (HlPT1L and HlPT2) obtained from a hop trichome-specific complementary DNA library were functionally characterized using this yeast system. Coexpression of codon-optimized PT1L and PT2 in yeast, together with upstream genes, led to the production of bitter acids, but no bitter acids were detected when either of the PT genes was expressed by itself. Stepwise mutation of the aspartate-rich motifs in PT1L and PT2 further revealed the prenylation sequence of these two enzymes in β-bitter acid biosynthesis: PT1L catalyzed only the first prenylation step, and PT2 catalyzed the two subsequent prenylation steps. A metabolon formed through interactions between PT1L and PT2 was demonstrated using a yeast two-hybrid system, reciprocal coimmunoprecipitation, and in vitro biochemical assays. These results provide direct evidence of the involvement of a functional metabolon of membrane-bound prenyltransferases in bitter acid biosynthesis in hop. PMID:25564559

  4. Synthesis of 24-phenyl-24-oxo steroids derived from bile acids by palladium-catalyzed cross coupling with phenylboronic acid. NMR characterization and X-ray structures.

    PubMed

    Mayorquín-Torres, Martha C; Romero-Ávila, Margarita; Flores-Álamo, Marcos; Iglesias-Arteaga, Martin A

    2013-11-01

    Palladium-catalyzed cross coupling of phenyboronic acid with acetylated bile acids in which the carboxyl functions have been activated by formation of a mixed anhydride with pivalic anhydride afforded moderate to good yield of 24-phenyl-24-oxo-steroids. Unambiguous assignments of the NMR signals were made with the aid of combined 1D and 2D NMR techniques. X-ray diffraction studies confirmed the obtained structures.

  5. Protease- and Acid-catalyzed Labeling Workflows Employing 18O-enriched Water

    PubMed Central

    Klingler, Diana; Hardt, Markus

    2013-01-01

    steps and reaction intermediates in complex proteolytic pathway reactions. Furthermore, the PALeO-reaction allows us to identify proteolytic enzymes such as the serine protease trypsin that is capable to rebind its cleavage products and catalyze the incorporation of a second 18O-atom. Such "double-labeling" enzymes can be used for postdigestion 18O-labeling, in which peptides are exclusively labeled by the carboxyl oxygen exchange reaction. Our third strategy extends labeling employing 18O-enriched water beyond enzymes and uses acidic pH conditions to introduce 18O-stable isotope signatures into peptides. PMID:23462971

  6. Unmasking the Action of Phosphinous Acid Ligands in Nitrile Hydration Reactions Catalyzed by Arene-Ruthenium(II) Complexes.

    PubMed

    Tomás-Mendivil, Eder; Cadierno, Victorio; Menéndez, María I; López, Ramón

    2015-11-16

    The catalytic hydration of benzonitrile and acetonitrile has been studied by employing different arene-ruthenium(II) complexes with phosphinous (PR2OH) and phosphorous acid (P(OR)2OH) ligands as catalysts. Marked differences in activity were found, depending on the nature of both the P-donor and η(6)-coordinated arene ligand. Faster transformations were always observed with the phosphinous acids. DFT computations unveiled the intriguing mechanism of acetonitrile hydration catalyzed by these arene-ruthenium(II) complexes. The process starts with attack on the nitrile carbon atom of the hydroxyl group of the P-donor ligand instead of on a solvent water molecule, as previously suggested. The experimental results presented herein for acetonitrile and benzonitrile hydration catalyzed by different arene-ruthenium(II) complexes could be rationalized in terms of such a mechanism.

  7. The fatty acid desaturase 2 (FADS2) gene product catalyzes Δ4 desaturation to yield n-3 docosahexaenoic acid and n-6 docosapentaenoic acid in human cells

    PubMed Central

    Park, Hui Gyu; Park, Woo Jung; Kothapalli, Kumar S. D.; Brenna, J. Thomas

    2015-01-01

    Docosahexaenoic acid (DHA) is a Δ4-desaturated C22 fatty acid and the limiting highly unsaturated fatty acid (HUFA) in neural tissue. The biosynthesis of Δ4-desaturated docosanoid fatty acids 22:6n-3 and 22:5n-6 are believed to proceed via a circuitous biochemical pathway requiring repeated use of a fatty acid desaturase 2 (FADS2) protein to perform Δ6 desaturation on C24 fatty acids in the endoplasmic reticulum followed by 1 round of β-oxidation in the peroxisomes. We demonstrate here that the FADS2 gene product can directly Δ4-desaturate 22:5n-3→22:6n-3 (DHA) and 22:4n-6→22:5n-6. Human MCF-7 cells lacking functional FADS2-mediated Δ6-desaturase were stably transformed with FADS2, FADS1, or empty vector. When incubated with 22:5n-3 or 22:4n-6, FADS2 stable cells produce 22:6n-3 or 22:5n-6, respectively. Similarly, FADS2 stable cells when incubated with d5-18:3n-3 show synthesis of d5-22:6n-3 with no labeling of 24:5n-3 or 24:6n-3 at 24 h. Further, both C24 fatty acids are shown to be products of the respective C22 fatty acids via elongation. Our results demonstrate that the FADS2 classical transcript mediates direct Δ4 desaturation to yield 22:6n-3 and 22:5n-6 in human cells, as has been widely shown previously for desaturation by fish and many other organisms.—Park, H. G., Park, W. J., Kothapalli, K. S. D., Brenna, J. T. The fatty acid desaturase 2 (FADS2) gene product catalyzes Δ4 desaturation to yield n-3 docosahexaenoic acid and n-6 docosapentaenoic acid in human cells. PMID:26065859

  8. Automation of High-Throughput Mass Spectrometry-Based Plasma N-Glycome Analysis with Linkage-Specific Sialic Acid Esterification.

    PubMed

    Bladergroen, Marco R; Reiding, Karli R; Hipgrave Ederveen, Agnes L; Vreeker, Gerda C M; Clerc, Florent; Holst, Stephanie; Bondt, Albert; Wuhrer, Manfred; van der Burgt, Yuri E M

    2015-09-01

    Glycosylation is a post-translational modification of key importance with heterogeneous structural characteristics. Previously, we have developed a robust, high-throughput MALDI-TOF-MS method for the comprehensive profiling of human plasma N-glycans. In this approach, sialic acid residues are derivatized with linkage-specificity, namely the ethylation of α2,6-linked sialic acid residues with parallel lactone formation of α2,3-linked sialic acids. In the current study, this procedure was used as a starting point for the automation of all steps on a liquid-handling robot system. This resulted in a time-efficient and fully standardized procedure with throughput times of 2.5 h for a first set of 96 samples and approximately 1 h extra for each additional sample plate. The mass analysis of the thus-obtained glycans was highly reproducible in terms of relative quantification, with improved interday repeatability as compared to that of manual processing.

  9. Copper-catalyzed aerobic decarboxylative sulfonylation of cinnamic acids with sodium sulfinates: stereospecific synthesis of (E)-alkenyl sulfones.

    PubMed

    Jiang, Qing; Xu, Bin; Jia, Jing; Zhao, An; Zhao, Yu-Rou; Li, Ying-Ying; He, Na-Na; Guo, Can-Cheng

    2014-08-15

    A copper-catalyzed aerobic decarboxylative sulfonylation of alkenyl carboxylic acids with sodium sulfinates is developed. This study offers a new and expedient strategy for stereoselective synthesis of (E)-alkenyl sulfones that are widely present in biologically active natural products and therapeutic agents. Moreover, the transformation is proposed to proceed via a radical process and exhibits a broad substrate scope and good functional group tolerance.

  10. Rh(III)-catalyzed selective coupling of N-methoxy-1H-indole-1-carboxamides and aryl boronic acids.

    PubMed

    Zheng, Jing; Zhang, Yan; Cui, Sunliang

    2014-07-01

    A Rh(III)-catalyzed selective coupling of N-methoxy-1H-indole-1-carboxamide and aryl boronic acids is reported. The coupling is mild and efficient toward diverse product formation, with selective C-C and C-C/C-N bond formation. Kinetic isotope effects studies were conducted to reveal a mechanism of C-H activation and electrophilic addition. PMID:24959967

  11. Selective formation of secondary amides via the copper-catalyzed cross-coupling of alkylboronic acids with primary amides.

    PubMed

    Rossi, Steven A; Shimkin, Kirk W; Xu, Qun; Mori-Quiroz, Luis M; Watson, Donald A

    2013-05-01

    For the first time, a general catalytic procedure for the cross-coupling of primary amides and alkylboronic acids is demonstrated. The key to the success of this reaction was the identification of a mild base (NaOSiMe3) and oxidant (di-tert-butyl peroxide) to promote the copper-catalyzed reaction in high yield. This transformation provides a facile, high-yielding method for the monoalkylation of amides. PMID:23611591

  12. Lewis acid catalyzed cascade reaction of 3-(2-benzenesulfonamide)propargylic alcohols to spiro[indene-benzosultam]s.

    PubMed

    Sun, Lang; Zhu, Yuanxun; Wang, Jing; Lu, Ping; Wang, Yanguang

    2015-01-16

    A highly efficient and convenient construction of the spiro[indene-benzosultam] skeleton from propargylic alcohols has been developed. The reaction proceeded in a Lewis acid catalyzed cascade process, including the trapping of allene carbocation with sulfonamide, electrophilic cyclization, and intramolecular Friedel-Crafts alkylation. In the presence of NIS or NBS, iodo/bromo-substituted spiro[indene-benzosultam]s could be prepared in excellent yields. PMID:25541815

  13. Study of the kinetics and equilibria of the oligomerization reactions of 2-methylglyceric acid

    NASA Astrophysics Data System (ADS)

    Birdsall, A. W.; Zentner, C. A.; Elrod, M. J.

    2013-03-01

    The presence of a variety of chemical species related to the gaseous precursor isoprene in ambient secondary organic aerosol (SOA) has stimulated investigations of the nature of SOA-phase chemical processing. Recent work has demonstrated that 2-methylglyceric acid (2-MG) is an important isoprene-derived ambient SOA component and atmospheric chamber experiments have suggested that 2-MG may exist in oligomeric form (as oligoesters) under conditions of low SOA water content. In order to better understand the thermodynamic and kinetic parameters of such oligomerization reactions, nuclear magnetic resonance techniques were used to study the bulk phase acid-catalyzed aqueous reactions (Fischer esterification) of 2-MG. While the present results indicate that 2-MG oligoesters are formed in the bulk phase with similar water content equilibrium dependences as observed in atmospheric chamber SOA experiments, the acid-catalyzed rate of the Fischer esterification mechanism may be too slow to rationalize the 2-MG oligoester production timescales observed in the atmospheric chamber experiments. Furthermore, it appears that unrealistically high ambient SOA acidities would also be required for significant 2-MG oligoester content to arise via Fischer esterification. Therefore, the present results suggest that other, more kinetically facile, esterification mechanisms may be necessary to rationalize the existence of 2-MG oligomers in atmospheric chamber-generated and ambient SOA.

  14. Study of the kinetics and equilibria of the oligomerization reactions of 2-methylglyceric acid

    NASA Astrophysics Data System (ADS)

    Birdsall, A. W.; Zentner, C. A.; Elrod, M. J.

    2012-11-01

    The presence of a variety of chemical species related to the gaseous precursor isoprene in ambient secondary organic aerosol (SOA) has stimulated investigations of the nature of SOA-phase chemical processing. Recent work has demonstrated that 2-methylglyceric acid (2-MG) is an important isoprene-derived ambient SOA component and atmospheric chamber experiments have suggested that 2-MG may exist in oligomeric form (as oligoesters) under conditions of low SOA water content. In order to better understand the thermodynamic and kinetic parameters of such oligomerization reactions, nuclear magnetic resonance techniques were used to study the bulk phase acid-catalyzed aqueous reactions (Fischer esterification) of 2-MG. While the present results indicate that 2-MG oligoesters are formed in the bulk phase with similar water content equilibrium dependences as observed in atmospheric chamber SOA experiments, the acid-catalyzed rate of the Fischer esterification mechanism may be too slow to rationalize the 2-MG oligoester production timescales observed in the atmospheric chamber experiments. Furthermore, it appears that unrealistically high ambient SOA acidities would also be required for significant 2-MG oligoester content to arise via Fischer esterification. Therefore, the present results suggest that other, more kinetically facile, esterification mechanisms may be necessary to rationalize the existence of 2-MG oligomers in atmospheric chamber-generated and ambient SOA.

  15. Isofunctional enzymes PAD1 and UbiX catalyze formation of a novel cofactor required by ferulic acid decarboxylase and 4-hydroxy-3-polyprenylbenzoic acid decarboxylase.

    PubMed

    Lin, Fengming; Ferguson, Kyle L; Boyer, David R; Lin, Xiaoxia Nina; Marsh, E Neil G

    2015-04-17

    The decarboxylation of antimicrobial aromatic acids such as phenylacrylic acid (cinnamic acid) and ferulic acid by yeast requires two enzymes described as phenylacrylic acid decarboxylase (PAD1) and ferulic acid decarboxylase (FDC). These enzymes are of interest for various biotechnological applications, such as the production of chemical feedstocks from lignin under mild conditions. However, the specific role of each protein in catalyzing the decarboxylation reaction remains unknown. To examine this, we have overexpressed and purified both PAD1 and FDC from E. coli. We demonstrate that PAD1 is a flavin mononucleotide (FMN)-containing protein. However, it does not function as a decarboxylase. Rather, PAD1 catalyzes the formation of a novel, diffusible cofactor required by FDC for decarboxylase activity. Coexpression of FDC and PAD1 results in the production of FDC with high levels cofactor bound. Holo-FDC catalyzes the decarboxylation of phenylacrylic acid, coumaric acid and ferulic acid with apparent kcat ranging from 1.4-4.6 s(-1). The UV-visible and mass spectra of the cofactor indicate that it appears to be a novel, modified form of reduced FMN; however, its instability precluded determination of its structure. The E. coli enzymes UbiX and UbiD are related by sequence to PAD1 and FDC respectively and are involved in the decarboxylation of 4-hydroxy-3-octaprenylbenzoic acid, an intermediate in ubiquinone biosynthesis. We found that endogenous UbiX can also activate FDC. This implies that the same cofactor is required for decarboxylation of 4-hydroxy-3-polyprenylbenzoic acid by UbiD and suggests a wider role for this cofactor in metabolism.

  16. Reactivity of Cations and Zwitterions Formed in Photochemical and Acid-Catalyzed Reactions from m-Hydroxycycloalkyl-Substituted Phenol Derivatives.

    PubMed

    Cindro, Nikola; Antol, Ivana; Mlinarić-Majerski, Kata; Halasz, Ivan; Wan, Peter; Basarić, Nikola

    2015-12-18

    Three m-substituted phenol derivatives, each with a labile benzylic alcohol group and bearing either protoadamantyl 4, homoadamantyl 5, or a cyclohexyl group 6, were synthesized and their thermal acid-catalyzed and photochemical solvolytic reactivity studied, using preparative irradiations, fluorescence measurements, nanosecond laser flash photolysis, and quantum chemical calculations. The choice of m-hydroxy-substitution was driven by the potential for these phenolic systems to generate m-quinone methides on photolysis, which could ultimately drive the excited-state pathway, as opposed to forming simple benzylic carbocations in the corresponding thermal route. Indeed, thermal acid-catalyzed reactions gave the corresponding cations, which undergo rearrangement and elimination from 4, only elimination from 5, and substitution and elimination from 6. On the other hand, upon photoexcitation of 4-6 to S1 in a polar protic solvent, proton dissociation from the phenol, coupled with elimination of the benzylic OH (as hydroxide ion) gave zwitterions (formal m-quinone methides). The zwitterions exhibit reactivity different from the corresponding cations due to a difference in charge distribution, as shown by DFT calculations. Thus, protoadamantyl zwitterion has a less nonclassical character than the corresponding cation, so it does not undergo 1,2-shift of the carbon atom, as observed in the acid-catalyzed reaction. PMID:26595342

  17. Kinetic resolution of racemic α-hydroxyphosphonates by asymmetric esterification using achiral carboxylic acids with pivalic anhydride and a chiral acyl-transfer catalyst.

    PubMed

    Shiina, Isamu; Ono, Keisuke; Nakahara, Takayoshi

    2013-11-25

    A practical protocol is developed to directly provide chiral α-acyloxyphosphonates and α-hydroxyphosphonates from (±)-α-hydroxyphosphonates utilizing the transacylation process to generate the mixed anhydrides from acid components and pivalic anhydride in the presence of organocatalysts (s-value = 33-518).

  18. Abrogating Cholesterol Esterification Suppresses Growth and Metastasis of Pancreatic Cancer

    PubMed Central

    Li, Junjie; Gu, Dongsheng; Lee, Steve Seung-Young; Song, Bing; Bandyopadhyay, Shovik; Chen, Shaoxiong; Konieczny, Stephen F.; Ratliff, Timothy L.; Liu, Xiaoqi; Xie, Jingwu; Cheng, Ji-Xin

    2016-01-01

    Cancer cells are known to execute reprogramed metabolism of glucose, amino acids, and lipids. Here, we report a significant role of cholesterol metabolism in cancer metastasis. By employing label-free Raman spectromicroscopy, we found an aberrant accumulation of cholesteryl ester in human pancreatic cancer specimens and cell lines, mediated by acyl-CoA cholesterol acyltransferase-1 (ACAT-1) enzyme. Expression of ACAT-1 showed a correlation with poor patient survival. Abrogation of cholesterol esterification, either by an ACAT-1 inhibitor or by shRNA knockdown, significantly suppressed tumor growth and metastasis in an orthotopic mouse model of pancreatic cancer. Mechanically, ACAT-1 inhibition increased intracellular free cholesterol level, which was associated with elevated endoplasmic reticulum stress and caused apoptosis. Collectively, our results demonstrate a new strategy for treating metastatic pancreatic cancer by inhibiting cholesterol esterification. PMID:27132508

  19. Palladium-catalyzed mono-N-allylation of unprotected anthranilic acids with allylic alcohols in aqueous media.

    PubMed

    Hikawa, Hidemasa; Yokoyama, Yuusaku

    2011-10-21

    Palladium-catalyzed N-allylation of anthranilic acids 1a-j with allyl alcohol 2a in the presence of Pd(OAc)(2), sodium diphenylphosphinobenzene-3-sulfonate (TPPMS) in THF-H(2)O at room temperature gave only mono-N-allylated anthranilic acids 3a-j in good yields (70-98%). The reactions of 4-bromoanthranilic acid 1i with 2-methyl-3-buten-2-ol 2b showed complete chemoselectivity in N-allylation (neutral conditions) and C-vinylation (basic conditions). In our catalytic system, the keys to success are use of an unprotected anthranilic acid as a starting material and the presence of water in the reaction medium. The carboxyl group of anthranilic acid and water may play important roles for the smooth generation of the π-allyl palladium species by activation of the hydroxyl group of the allylic alcohol. PMID:21919524

  20. Acid-catalyzed conversion of mono- and poly-sugars into platform chemicals: effects of molecular structure of sugar substrate.

    PubMed

    Hu, Xun; Wu, Liping; Wang, Yi; Song, Yao; Mourant, Daniel; Gunawan, Richard; Gholizadeh, Mortaza; Li, Chun-Zhu

    2013-04-01

    Hydrolysis/pyrolysis of lignocellulosic biomass always produces a mixture of sugars with distinct structures as intermediates or products. This study tried to elucidate the effects of molecular structure of sugars on their acid-catalyzed conversions in ethanol/water. Location of carbonyl group in sugars (fructose versus glucose) and steric configuration of hydroxyl groups (glucose versus galactose) significantly affected yields of levulinic acid/ester (fructose>glucose>galactose). The dehydration of fructose to 5-(hydroxymethyl)furfural produces much less soluble polymer than that from glucose and galactose, which results in high yields of levulinic acid/ester from fructose. Anhydrate sugar such as levoglucosan tends to undergo the undesirable decomposition to form less levulinic acid/ester. Catalytic behaviors of the poly-sugars (sucrose, maltose, raffinose, β-cyclodextrins) were determined much by their basic units. However, their big molecular sizes create the steric hindrance that significantly affects their followed conversion over solid acid catalyst. PMID:23454803

  1. Acid-Catalyzed Conversion of Furfuryl Alcohol to Ethyl Levulinate in Liquid Ethanol

    PubMed Central

    González Maldonado, Gretchen M.; Assary, Rajeev S.; Dumesic, James; Curtiss, Larry A.

    2014-01-01

    Reaction pathways for the acid-catalyzed conversion of furfuryl alcohol (FAL) to ethyl levulinate (EL) in ethanol were investigated using liquid chromatography-mass spectrometry (LC-MS), 1D and 2D nuclear magnetic resonance (NMR) spectroscopy, and ab initio high-level quantum chemical (G4MP2) calculations. Our combined studies show that the production of EL at high yields from FAL is not accompanied by stoichiometric production of diethyl either (DEE), indicating that ethoxymethyl furan (EMF) is not an intermediate in the major reaction pathway. Several intermediates were observed using an LC-MS system, and three of these intermediates were isolated and subjected to reaction conditions. The structures of two intermediates were elucidated using 1D and 2D NMR techniques. One of these intermediates is EMF, which forms EL and DEE in a secondary reaction pathway. The second intermediate identified is 4,5,5-triethoxypentan-2-one, which is analogous to one of the intermediates observed in the conversion of FAL to LA in water (i.e. 4,5,5-trihydroxypentan-2-one). Furthermore, conversion of this intermediate to EL again involves the formation of DEE, indicating that it is also part of a secondary pathway. The primary pathway for production of EL involves solvent-assisted transfer of a water molecule from the partially detached protonated hydroxyl group of FAL to a ring carbon, followed by intra-molecular hydrogen shift, where the apparent reaction barrier for the hydrogen shift is relatively smaller in ethanol (21.1 kcal/mol) than that in water (26.6 kcal/mol). PMID:25035710

  2. Iodine-Catalyzed Decarboxylative Amidation of β,γ-Unsaturated Carboxylic Acids with Chloramine Salts Leading to Allylic Amides.

    PubMed

    Kiyokawa, Kensuke; Kojima, Takumi; Hishikawa, Yusuke; Minakata, Satoshi

    2015-10-26

    The iodine-catalyzed decarboxylative amidation of β,γ-unsaturated carboxylic acids with chloramine salts is described. This method enables the regioselective synthesis of allylic amides from various types of β,γ-unsaturated carboxylic acids containing substituents at the α- and β-positions. In the reaction, N-iodo-N-chloroamides, generated by the reaction of a chloramine salt with I2 , function as a key active species. The reaction provides an attractive alternative to existing methods for the synthesis of useful secondary allylic amine derivatives. PMID:26493878

  3. Brønsted Acid Catalyzed Asymmetric Hydroamination of Alkenes: Synthesis of Pyrrolidines Bearing a Tetrasubstituted Carbon Stereocenter.

    PubMed

    Lin, Jin-Shun; Yu, Peng; Huang, Lin; Zhang, Pan; Tan, Bin; Liu, Xin-Yuan

    2015-06-26

    The first highly enantioselective Brønsted acid catalyzed intramolecular hydroamination of alkenes enables the efficient construction of a series of chiral (spirocyclic) pyrrolidines with an α-tetrasubstituted carbon stereocenter with excellent functional group tolerance. A unique feature of this strategy is the use of a thiourea group acting as both the activating and the directing group through cooperative multiple hydrogen bonding with a Brønsted acid and the double bond. The utility of this method is highlighted by the facile construction of chiral synthetic intermediates and important structural motifs that are widely found in organic synthesis.

  4. Kinetic resolution of racemic 2-hydroxy-γ-butyrolactones by asymmetric esterification using diphenylacetic acid with pivalic anhydride and a chiral acyl-transfer catalyst.

    PubMed

    Nakata, Kenya; Gotoh, Kouya; Ono, Keisuke; Futami, Kengo; Shiina, Isamu

    2013-03-15

    Various optically active 2-hydroxy-γ-butyrolactone derivatives are produced via the kinetic resolution of racemic 2-hydroxy-γ-butyrolactones with diphenylacetic acid using pivalic anhydride and (R)-benzotetramisole ((R)-BTM), a chiral acyl-transfer catalyst. Importantly, the substrate scope of this novel protocol is fairly broad (12 examples, s-value; up to over 1000). In addition, we succeeded in disclosing the reaction mechanism to afford high enantioselectivity using theoretical calculations and expounded on the substituent effects at the C-3 positions in 2-hydroxylactones.

  5. Esterification of bio-oil from mallee (Eucalyptus loxophleba ssp. gratiae) leaves with a solid acid catalyst: Conversion of the cyclic ether and terpenoids into hydrocarbons.

    PubMed

    Hu, Xun; Gunawan, Richard; Mourant, Daniel; Wang, Yi; Lievens, Caroline; Chaiwat, Weerawut; Wu, Liping; Li, Chun-Zhu

    2012-11-01

    Bio-oil from pyrolysis of mallee (Eucalyptus loxophleba ssp. gratiae) leaves differs from that obtained with wood by its content of cyclic ethers, terpenoids and N-containing organic compounds. Upgrading of the leaf bio-oil in methanol with a solid acid catalyst was investigated and it was found that the N-containing organics in the bio-oil lead to deactivation of the catalyst in the initial stage of exposure and have to be removed via employing high catalyst loading to allow the occurrence of other acid-catalysed reactions. Eucalyptol, the main cyclic ether in the bio-oil, could be converted into the aromatic hydrocarbon, p-cymene, through a series of intermediates including α-terpineol, terpinolene, and α-terpinene. Various steps such as ring-opening, dehydration, isomerisation, and aromatization were involved in the conversion of eucalyptol. The terpenoids in bio-oil could also be converted into aromatic hydrocarbons that can serve as starting materials for the synthesis of fine chemicals, via the similar processes.

  6. Ring-opening polymerization of ε-caprolactone catalyzed by sulfonic acids: computational evidence for bifunctional activation.

    PubMed

    Susperregui, Nicolas; Delcroix, Damien; Martin-Vaca, Blanca; Bourissou, Didier; Maron, Laurent

    2010-10-01

    The mechanism of ring-opening of ε-caprolactone by methanol catalyzed by trifluoromethane and methane sulfonic acids has been studied computationally at the DFT level of theory. For both elementary steps, the sulfonic acid was predicted to behave as a bifunctional catalyst. The nucleophilic addition proceeds via activation of both the monomer and the alcohol. The ring-opening involves the cleavage of the endo C-O bond of the tetrahedral intermediate with concomitant proton transfer. In both cases, the sulfonic acid acts as a proton shuttle via its acidic hydrogen atom and basic oxygen atoms. The computed activation barriers are consistent with the relatively fast polymerizations observed experimentally at room temperature with both catalysts.

  7. Practical synthesis of enantiomerically pure beta2-amino acids via proline-catalyzed diastereoselective aminomethylation of aldehydes.

    PubMed

    Chi, Yonggui; English, Emily P; Pomerantz, William C; Horne, W Seth; Joyce, Leo A; Alexander, Lane R; Fleming, William S; Hopkins, Elizabeth A; Gellman, Samuel H

    2007-05-01

    Proline-catalyzed diastereoselective aminomethylation of aldehydes using a chiral iminium ion, generated from a readily prepared precursor, provides alpha-substituted-beta-amino aldehydes with 85:15 to 90:10 dr. The alpha-substituted-beta-amino aldehydes can be reduced to beta-substituted-gamma-amino alcohols, the major diastereomer of which can be isolated via crystallization or column chromatography. The amino alcohols are efficiently transformed to protected beta2-amino acids, which are valuable building blocks for beta-peptides, natural products, and other interesting molecules. Because conditions for the aminomethylation and subsequent reactions are mild, beta2-amino acid derivatives with protected functional groups in the side chain, such as beta2-homoglutamic acid, beta2-homotyrosine, and beta2-homolysine, can be prepared in this way. The synthetic route is short, and purifications are simple; therefore, this method enables the preparation of protected beta2-amino acids in useful quantities.

  8. Applications of FT-IR spectroscopy to the studies of esterification and crosslinking of cellulose by polycarboxylic acids: Part II. The performance of the crosslinked cotton fabrics

    NASA Astrophysics Data System (ADS)

    Wei, Weishu; Yang, Charles Q.

    1998-06-01

    Durable press finishing processes are commonly used in the textile industry to produce wrinkle-free cotton fabrics and garments. A durable press finishing agent forms covalent bands with cellulosic hydroxyl groups, thus crosslinking the cellulose molecules. The crosslinking of cellulose increases wrinkle resistance of the treated cotton fabric and reduces fabric mechanical strength. Wrinkle recovery angle (WRA) and tensile strength are the two most important parameters used to evaluate the performance of the crosslinked cotton fabrics and garments. In this study, we investigated the correlation between WRA and tensile strength on one hand, and the amount of crosslinkages formed by the crosslinking agents including dimethyloldihydroxylethyleneurea (DMDHEU) and 1,2,3,4-butanetetracarboxylic acid (BTCA) determined by FT-IR spectroscopy on the other hand. Linear regression curves between the carbonyl band absorbance, and WRA and tensile strength of the treated cotton fabric were developed. The data indicated that FT-IR spectroscopy is a reliable technique for predicting the performance of durable press finished cotton fabrics, therefore can be used as a convenient instrumental method for quality control in the textile and garment industry.

  9. Homoserine Esterification in Green Plants

    PubMed Central

    Giovanelli, John; Mudd, S. Harvey; Datko, Anne H.

    1974-01-01

    Extracts of phylogenetically diverse plans were surveyed for their ability to synthesize the following homoserine esters which are potential precursors for methionine and threonine synthesis in green plants: O-acetyl-, O-oxalyl-, O-succinyl-, O-malonyl-, and O-phosphohomoserine. Synthesis of O-acylhomoserine esters was detected only in Pisum sativum L. and Lathyrus sativus L. Extracts of P. sativum, a plant known to accumulate O-acetylhomoserine, catalyzed the specific synthesis of this ester from homoserine and acetyl-CoA. Extracts of L. sativus, a plant known to accumulate O-oxalylhomoserine, catalyzed the specific synthesis of this ester from homoserine and oxalyl-CoA. None of the other plants surveyed, including representatives of the green algae, horsetails, gymnosperms, and angiosperms, catalyzed the synthesis of any of the O-acylhomoserine esters studied. In contrast, synthesis of O-phosphohomoserine by the reaction catalyzed by homoserine kinase was demonstrated in extracts of all plants examined, including the two exceptional legumes. These results suggest that, among the five homoserine esters studied, O-phosphohomoserine is the major activated homoserine derivative in plants. Direct confirmation of the dominant physiological role of O-phosphohomoserine in the synthesis of cystathionine in the transsulfuration pathway of methionine biosynthesis in plants has recently been provided (Datko, A. H., Giovanelli, J., and Mudd, S. H. 1974. J. Biol. Chem. 249: 1139-1155). PMID:16658961

  10. Protein kinase activators alter glial cholesterol esterification

    SciTech Connect

    Jeng, I.; Dills, C.; Klemm, N.; Wu, C.

    1986-05-01

    Similar to nonneural tissues, the activity of glial acyl-CoA cholesterol acyltransferase is controlled by a phosphorylation and dephosphorylation mechanism. Manipulation of cyclic AMP content did not alter the cellular cholesterol esterification, suggesting that cyclic AMP is not a bioregulator in this case. Therefore, the authors tested the effect of phorbol-12-myristate 13-acetate (PMA) on cellular cholesterol esterification to determine the involvement of protein kinase C. PMA has a potent effect on cellular cholesterol esterification. PMA depresses cholesterol esterification initially, but cells recover from inhibition and the result was higher cholesterol esterification, suggesting dual effects of protein kinase C. Studies of other phorbol analogues and other protein kinase C activators such as merezein indicate the involvement of protein kinase C. Oleoyl-acetyl glycerol duplicates the effect of PMA. This observation is consistent with a diacyl-glycerol-protein kinase-dependent reaction. Calcium ionophore A23187 was ineffective in promoting the effect of PMA. They concluded that a calcium-independent and protein C-dependent pathway regulated glial cholesterol esterification.

  11. Sulfonic acid resin-catalyzed addition of phenols, carboxylic acids, and water to olefins: Model reactions for catalytic upgrading of bio-oil.

    PubMed

    Zhang, Zhi-Jun; Wang, Qing-Wen; Yang, Xu-Lai; Chatterjee, Sabornie; Pittman, Charles U

    2010-05-01

    Acid-catalyzed 1-octene reactions with phenol and mixtures of phenol with water, acetic acid and 1-butanol were studied as partial bio-oil upgrading models. Bio-oil from fast biomass pyrolysis has poor fuel properties due to the presence of substantial amounts of water, carboxylic acid, phenolic derivatives and other hydroxyl-containing compounds. Additions across olefins offer a route to simultaneously lower water content and acidity while increasing hydrophobicity, stability and heating value. Amberlyst15, Dowex50WX2 and Dowex50WX4 effectively catalyzed phenol O- and C-alkylation from 65 to 120 degrees C, giving high O-alkylation selectivities in the presence of water, acetic acid and 1-butanol. Octanols and dioctyl ethers were formed from water and octyl acetates and phenol acetates from acetic acid. Phenol alkylation slowed in the presence of water. Dowex50WX2 and Dowex50WX4 were more stable in the presence of water than Amberlyst15 and were successfully recycled. Adding 1-butanol to phenol/water/1-octene, gave emulsion-like mixtures which improved phenol conversion and olefin hydration.

  12. Esterification Reaction Utilizing Sense of Smell and Eyesight for Conversion and Catalyst Recovery Monitoring

    ERIC Educational Resources Information Center

    Janssens, Nikki; Wee, Lik H.; Martens, Johan A.

    2014-01-01

    The esterification reaction of salicylic acid with ethanol is performed in presence of dissolved 12-tungstophosphoric Brønsted-Lowry acid catalyst, a Keggin-type polyoxometalate (POM). The monitoring of the reaction with smell and the recovery of the catalyst with sight is presented. Formation of the sweet-scented ester is apparent from the smell.…

  13. Lewis Acid Catalyzed Ring-opening Polymerization of Epoxidized Soybean Oil in Liquid Carbon Dioxide

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Ring-opening polymerization of epoxidized soybean oil (ESO) catalyzed by boron trifluoride diethyl etherate (BF3•OEt2), in liquid carbon dioxide, was conducted in an effort to develop useful biobased biodegradable polymers. The resulting polymers (RPESO) were characterized by FTIR spectroscopy, diff...

  14. Hyaluronic acid-based hydrogels crosslinked by copper-catalyzed azide-alkyne cycloaddition with tailorable mechanical properties.

    PubMed

    Piluso, Susanna; Hiebl, Bernhard; Gorb, Stanislav N; Kovalev, Alexander; Lendlein, Andreas; Neffe, Axel T

    2011-02-01

    Biopolymers of the extracellular matrix are attractive starting materials for providing degradable and biocompatible biomaterials. In this study, hyaluronic acid-based hydrogels with tunable mechanical properties were prepared by the use of copper- catalyzed azide-alkyne cycloaddition (known as "click chemistry"). Alkyne-functionalized hyaluronic acid was crosslinked with linkers having two terminal azide functionalities, varying crosslinker density as well as the lengths and rigidity of the linker molecules. By variation of the crosslinker density and crosslinker type, hydrogels with elastic moduli in the range of 0.5-4 kPa were prepared. The washed materials contained a maximum of 6.8 mg copper per kg dry weight and the eluate of the gel crosslinked with diazidostilbene did not show toxic effects on L929 cells. The hyaluronic acid-based hydrogels have potential as biomaterials for cell culture or soft tissue regeneration applications. PMID:21374560

  15. Flow-injection determination of hydrogen peroxide based on fluorescence quenching of chromotropic acid catalyzed with Fe(II).

    PubMed

    Li, Zhen Hai; Li, Dong Hao; Oshita, Koji; Motomizu, Shoji

    2010-09-15

    Flow-injection analysis system (FIA system), which was based on Fe(II)-catalyzed oxidation of chromotropic acid with hydrogen peroxide, was developed for the determination of hydrogen peroxide. The chromotropic acid has a fluorescence measured at lambda(em)=440 nm (emission wavelength) with lambda(ex)=235 nm (excitation wavelength), and the fluorescence intensity at lambda(em)=440 nm quietly decreased in the presence of hydrogen peroxide and Fe(II), which was caused by Fe(II)-catalyzed oxidation of chromotropic acid with hydrogen peroxide. By measuring the difference of fluorescence intensity, hydrogen peroxide (1.0 x 10(-8)-1.0 x 10(-3) mol L(-1)) could be determined by the proposed FIA system, whose analytical throughput was 40 samples h(-1). The relative standard deviation (RSD) was 1.03% (n=10) for 4.0 x 10(-8) mol L(-1) hydrogen peroxide. The proposed FIA technique could be applied to the determination of hydrogen peroxide in rain water samples.

  16. β-Amino acid catalyzed asymmetric Michael additions: design of organocatalysts with catalytic acid/base dyad inspired by serine proteases.

    PubMed

    Yang, Hui; Wong, Ming Wah

    2011-09-16

    A new type of chiral β-amino acid catalyst has been computationally designed, mimicking the enzyme catalysis of serine proteases. Our catalyst approach is based on the bioinspired catalytic acid/base dyad, namely, a carboxyl and imidazole pair. DFT calculations predict that this designed organocatalyst catalyzes Michael additions of aldehydes to nitroalkenes with excellent enantioselectivities and remarkably high anti diastereoselectivities. The unusual stacked geometry of the enamine intermediate, hydrogen bonding network, and the adoption of an exo transition state are the keys to understand the stereoselectivity.

  17. Silver-catalyzed double-decarboxylative cross-coupling of α-keto acids with cinnamic acids in water: a strategy for the preparation of chalcones.

    PubMed

    Zhang, Ning; Yang, Daoshan; Wei, Wei; Yuan, Li; Nie, Fafa; Tian, Laijin; Wang, Hua

    2015-03-20

    A silver-catalyzed double-decarboxylative protocol has been proposed for the construction of chalcone derivatives via cascade coupling of substituted α-keto acids with cinnamic acids under the mild aqueous conditions. The developed method for constructing C-C bonds via double-decarboxylative reactions is efficient, practical, and environmentally benign by using the readily available starting materials. It should provide a promising synthesis candidate for the formation of diverse and useful chalcone derivatives in the fields of synthetic and pharmaceutical chemistry.

  18. Influence of organic acids on oscillations and waves in the ferroin-catalyzed Belousov-Zhabotinsky reaction

    NASA Astrophysics Data System (ADS)

    Krüger, Frank; Nagy-Ungvárai, Zsuzsanna; Müller, Stefan C.

    Experiments of the influence of mesoxalic and tartronic acid on the oscillatory behavior and on the spiral tip motion in a ferroin-catalyzed Belousov-Zhabotinsky (BZ) solution are reported. The oscillations were observed in batch and CSTR systems, and for the investigations of the spiral tip motion an open gel reactor was used. A characteristic shoulder in the oscillations is associated with an additional Br - production phase. The chemical parameters for a transition from a hypocycloidal to a circular tip trajectory are found. The findings are compared with the temporal and spatial dynamic behavior, occurring during the ageing process of the solution.

  19. Brönsted Acid-Catalyzed One-Pot Synthesis of Indoles from o-Aminobenzyl Alcohols and Furans

    PubMed Central

    Kuznetsov, Alexey; Makarov, Anton; Rubtsov, Alexandr E.; Butin, Alexander V.; Gevorgyan, Vladimir

    2013-01-01

    Brönsted acid-catalyzed one-pot synthesis of indoles from o-aminobenzyl alcohols and furans has been developed. This method operates via the in situ formation of aminobenzylfuran, followed by its recyclization into the indole core. The method proved to be efficient for substrates possessing different functional groups, including -OMe, -CO2Cy, and -Br. The resulting indoles can easily be transformed into diverse scaffolds, including 2,3- and 1,2-fused indoles, and indole possessing an α,β-unsaturated ketone moiety at the C-2 position. PMID:24255969

  20. Palladium-Catalyzed Defluorinative Coupling of 1-Aryl-2,2-Difluoroalkenes and Boronic Acids: Stereoselective Synthesis of Monofluorostilbenes.

    PubMed

    Thornbury, Richard T; Toste, F Dean

    2016-09-12

    The palladium-catalyzed defluorinative coupling of 1-aryl-2,2-difluoroalkenes with boronic acids is described. Broad functional-group tolerance arises from a redox-neutral process by a palladium(II) active species which is proposed to undergo a β-fluoride elimination to afford the products. The monofluorostilbene products were formed with excellent diastereoselectivity (≥50:1) in all cases, and it is critical, as traditional chromatographic techniques often fail to separate monofluoroalkene isomers. As a demonstration of this method's unique combination of reactivity and functional-group tolerance, a Gleevec® analogue, using a monofluorostilbene as an amide isostere, was synthesized. PMID:27511868

  1. Palladium-Catalyzed Oxidative Sulfenylation of Indoles and Related Electron-Rich Heteroarenes with Aryl Boronic Acids and Elemental Sulfur.

    PubMed

    Li, Jianxiao; Li, Chunsheng; Yang, Shaorong; An, Yanni; Wu, Wanqing; Jiang, Huanfeng

    2016-09-01

    An efficient and convenient palladium-catalyzed C-H bond oxidative sulfenylation of indoles and related electron-rich heteroarenes with aryl boronic acids and elemental sulfur has been described. This procedure provides a useful and direct approach for the assembly of a wide range of structurally diverse 3-sulfenylheteroarenes with moderate to excellent yields from simple and readily available starting materials. Moreover, this synthetic protocol is suitable for N-protected and unprotected indoles. Notably, the construction of two C-S bonds in one step was also achieved in this transformation. PMID:27500941

  2. Palladium-Catalyzed 1,3-Difunctionalization Using Terminal Alkenes with Alkenyl Nonaflates and Aryl Boronic Acids.

    PubMed

    McCammant, Matthew S; Shigeta, Takashi; Sigman, Matthew S

    2016-04-15

    A Pd-catalyzed 1,3-difunctionalization of terminal alkenes using 1,1-disubstituted alkenyl nonaflates and arylboronic acid coupling partners is reported. This transformation affords allylic arene products that are difficult to selectively access using traditional Heck cross-coupling methodologies. The evaluation of seldom employed 1,1-disubstituted alkenyl nonaflate coupling partners led to the elucidation of subtle mechanistic features of π-allyl stabilized Pd-intermediates. Good stereo- and regioselectivity for the formation of 1,3-addition products can be accessed through a minimization of steric interactions that emanate from alkenyl nonaflate substitution.

  3. Convenient and Simple Esterification in Continuous-Flow Systems using g-DMAP.

    PubMed

    Okuno, Yoshinori; Isomura, Shigeki; Sugamata, Anna; Tamahori, Kaoru; Fukuhara, Ami; Kashiwagi, Miyu; Kitagawa, Yuuichi; Kasai, Emiri; Takeda, Kazuyoshi

    2015-11-01

    The utility and applicability of polyethylene-g-polyacrylic acid-immobilized dimethylaminopyridine (g-DMAP) as a catalyst in a continuous-flow system were investigated for decarboxylative esterification. High catalytic activity toward acylation was provided by g-DMAP containing a flexible grafted-polymer structure. During decarboxylation, carboxylic acids and alcohols were converted cleanly using di-tert-butyl dicarbonate (Boc2O) as a coupling reagent, which reduced by-products. In addition, the use of Boc2O resulted in the formation of tert-butyl esters. These esterifications dramatically reduced the reaction time under continuous-flow conditions, with a residence time of approximately 2 min. This highly efficient esterification procedure will provide more practical industrial applications.

  4. Towards determination of the distribution of methyl esterification in pectin

    SciTech Connect

    Maness, N.O.; Mort, A.J. )

    1990-05-01

    A procedure for determining the distribution of methyl esterification in pectin will be described. The first step is quantitative and selective reduction of methyl esterified galacturonic acid to galactose. Treatment of the reduced pectin with anhydrous liquid HF at {minus}10C results in cleavage of the galactosyl linkages without cleaving the galacturonosyl linkages. From the resultant oligosaccharides the distribution of contiguous non-esterified galacturonic acid residues in the polymer can be determined. If the reduced pectin is instead treated with lithium in ethylenediamine, galacturonic acid residues are destroyed and oligomers containing contiguous galactose residues (methyl esterified galacturonic acid in the parent polymer) are obtained. The distribution of contiguously esterified and non-esterified galacturonic acid segments in the original polymer is determined by separation and quantitation of these oligomers by HPLC. Application to commercially available pectins and to pectins from cotton suspension culture cells walls will be presented.

  5. Characterization of a Cross-Linked Protein-Nucleic Acid Substrate Radical in the Reaction Catalyzed by RlmN

    SciTech Connect

    Silakov, Alexey; Grove, Tyler L.; Radle, Matthew I.; Bauerle, Matthew R.; Green, Michael T.; Rosenzweig, Amy C.; Boal, Amie K.; Booker, Squire J.

    2014-08-14

    RlmN and Cfr are methyltransferases/methylsynthases that belong to the radical S-adenosylmethionine superfamily of enzymes. RlmN catalyzes C2 methylation of adenosine 2503 (A2503) of 23S rRNA, while Cfr catalyzes C8 methylation of the exact same nucleotide, and will subsequently catalyze C2 methylation if the site is unmethylated. A key feature of the unusual mechanisms of catalysis proposed for these enzymes is the attack of a methylene radical, derived from a methylcysteine residue, onto the carbon center undergoing methylation to generate a paramagnetic protein–nucleic acid cross-linked species. This species has been thoroughly characterized during Cfr-dependent C8 methylation, but does not accumulate to detectible levels in RlmN-dependent C2 methylation. Herein, we show that inactive C118S/A variants of RlmN accumulate a substrate-derived paramagnetic species. Characterization of this species by electron paramagnetic resonance spectroscopy in concert with strategic isotopic labeling shows that the radical is delocalized throughout the adenine ring of A2503, although predominant spin density is on N1 and N3. Moreover, 13C hyperfine interactions between the radical and the methylene carbon of the formerly [methyl-13C]Cys355 residue show that the radical species exists in a covalent cross-link between the protein and the nucleic acid substrate. X-ray structures of RlmN C118A show that, in the presence of SAM, the substitution does not alter the active site structure compared to that of the wild-type enzyme. Together, these findings have new mechanistic implications for the role(s) of C118 and its counterpart in Cfr (C105) in catalysis, and suggest involvement of the residue in resolution of the cross-linked species via a radical mediated process

  6. Lewis Acid Catalyzed Friedel-Crafts Alkylation of Alkenes with Trifluoropyruvates.

    PubMed

    Xiang, Bin; Xu, Teng-Fei; Wu, Liang; Liu, Ren-Rong; Gao, Jian-Rong; Jia, Yi-Xia

    2016-05-01

    A Friedel-Crafts alkylation reaction of styrenes with trifluoropyruvates has been developed, which delivered allylic alcohols in excellent yields (up to 98%) using the Ni(ClO4)2·6H2O/bipyridine complex as a catalyst. The asymmetric reaction was catalyzed by the chiral Cu(OTf)2/bisoxazoline complex to afford the corresponding chiral allylic alcohols bearing trifluoromethylated quaternary stereogenic centers in moderate enantioselectivities (up to 75% ee). PMID:27028539

  7. Improved Synthesis of 5-Substituted 1H-Tetrazoles via the [3+2] Cycloaddition of Nitriles and Sodium Azide Catalyzed by Silica Sulfuric Acid

    PubMed Central

    Du, Zhenting; Si, Changmei; Li, Youqiang; Wang, Yin; Lu, Jing

    2012-01-01

    A silica supported sulfuric acid catalyzed [3+2] cycloaddition of nitriles and sodium azide to form 5-substituted 1H-tetrazoles is described. The protocol can provide a series of 5-substituted 1H-tetrazoles using silica sulfuric acid from nitriles and sodium azide in DMF in 72%–95% yield. PMID:22606004

  8. Ring-opening polymerization of epoxidized soybean oil catalyzed by the superacid, Fluroantimonic acid hexahydrate (HSbF6-6H2O)

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Ring-opening polymerization of epoxidized soybean oil (ESO) catalyzed by the super acid, fluroantimonic acid hexahydrate (HSbF6-6H2O), in ethyl acetate was conducted. The resulting polymers, SA-RPESO, were characterized using infrared spectroscopy, differential scanning calorimetry, thermogravimetri...

  9. Aromatic aldehyde-catalyzed gas-phase decarboxylation of amino acid anion via imine intermediate: An experimental and theoretical study

    NASA Astrophysics Data System (ADS)

    Xiang, Zhang

    2013-10-01

    It is generally appreciated that carbonyl compound can promote the decarboxylation of the amino acid. In this paper, we have performed the experimental and theoretical investigation into the gas-phase decarboxylation of the amino acid anion catalyzed by the aromatic aldehyde via the imine intermediate on the basis of the tandem mass spectrometry (MS/MS) technique and density functional theory (DFT) calculation. The results show that the aromatic aldehyde can achieve a remarkable catalytic effect. Moreover, the catalytic mechanism varies according to the type of amino acid: (i) The decarboxylation of α-amino acid anion is determined by the direct dissociation of the Csbnd C bond adjacent to the carboxylate, for the resulting carbanion can be well stabilized by the conjugation between α-carbon, Cdbnd N bond and benzene ring. (ii) The decarboxylation of non-α-amino acid anion proceeds via a SN2-like transition state, in which the dissociation of the Csbnd C bond adjacent to the carboxylate and attacking of the resulting carbanion to the Cdbnd N bond or benzene ring take place at the same time. Specifically, for β-alanine, the resulting carbanion preferentially attacks the benzene ring leading to the benzene anion, because attacking the Cdbnd N bond in the decarboxylation can produce the unstable three or four-membered ring anion. For the other non-α-amino acid anion, the Cdbnd N bond preferentially participates in the decarboxylation, which leads to the pediocratic nitrogen anion.

  10. Enantiodivergent Atroposelective Synthesis of Chiral Biaryls by Asymmetric Transfer Hydrogenation: Chiral Phosphoric Acid Catalyzed Dynamic Kinetic Resolution.

    PubMed

    Mori, Keiji; Itakura, Tsubasa; Akiyama, Takahiko

    2016-09-12

    Reported herein is an enantiodivergent synthesis of chiral biaryls by a chiral phosphoric acid catalyzed asymmetric transfer hydrogenation reaction. Upon treatment of biaryl lactols with aromatic amines and a Hantzsch ester in the presence of chiral phosphoric acid, dynamic kinetic resolution (DKR) involving a reductive amination reaction proceeded smoothly to furnish both R and S isomers of chiral biaryls with excellent enantioselectivities by proper choice of hydroxyaniline derivative. This trend was observed in wide variety of substrates, and various chiral biphenyl and phenyl naphthyl adducts were synthesized with satisfactory enantioselectivities in enantiodivergent fashion. The enantiodivergent synthesis of synthetically challenging, chiral o-tetrasubstituted biaryls were also accomplished, and suggests high synthetic potential of the present method. PMID:27491630

  11. Kinetics and mechanism of the acid-catalyzed decomposition of omega-diazoacetophenones and their o-carbomethyoxy derivatives

    SciTech Connect

    Denisova, T.G.

    1988-01-01

    The kinetics of the acid-catalyzed decomposition of omega-diazoacetophenones and their o-carbomethoxy derivatives have been studied and their rate constants and activation energies measured in dioxane-H/sub 2/O (D/sub 2/O) and aqueous (D/sub 2/O)-dioxane mixtures (40:60 by volume) in the presence of H/sub 2/SO/sub 4/ (D/sub 2/SO/sub 4/), as well as in acetic and deuteroacetic acids, in the temperature range 290-328 K. Based on the results of k/sub H//k/sub D/ and ..delta..S not identical to measurements, assumptions have been made concerning the mechanism of the catalytic decomposition of the indicated diazoketones.

  12. Synthesis of diverse β-quaternary ketones via palladium-catalyzed asymmetric conjugate addition of arylboronic acids to cyclic enones

    PubMed Central

    Holder, Jeffrey C.; Goodman, Emmett D.; Kikushima, Kotaro; Gatti, Michele; Marziale, Alexander N.; Stoltz, Brian M.

    2014-01-01

    The development and optimization of a palladium-catalyzed asymmetric conjugate addition of arylboronic acids to cyclic enone conjugate acceptors is described. These reactions employ air-stable and readily-available reagents in an operationally simple and robust transformation that yields β-quaternary ketones in high yields and enantioselectivities. Notably, the reaction itself is highly tolerant of atmospheric oxygen and moisture and therefore does not require the use of dry or deoxygenated solvents, specially purified reagents, or an inert atmosphere. The ring size and β-substituent of the enone are highly variable, and a wide variety of β-quaternary ketones can be synthesized. More recently, the use of NH4PF6 has further expanded the substrate scope to include heteroatom-containing arylboronic acids and β-acyl enone substrates. PMID:26461082

  13. Oxidative esterification via photocatalytic C-H activation

    EPA Science Inventory

    Direct oxidative esterification of alcohol via photocatalytic C-H activation has been developed using VO@g-C3N4 catalyst; an expeditious esterification of alcohols occurs under neutral conditions using visible light as the source of energy.

  14. Silver(I)-Catalyzed Iodination of Arenes: Tuning the Lewis Acidity of N-Iodosuccinimide Activation.

    PubMed

    Racys, Daugirdas T; Sharif, Salaheddin A I; Pimlott, Sally L; Sutherland, Andrew

    2016-02-01

    A mild and rapid method for the iodination of arenes that utilizes silver(I) triflimide as a catalyst for activation of N-iodosuccinimide has been developed. The transformation was found to be general for a wide range of anisole, aniline, acetanilide, and phenol derivatives and allowed the late-stage iodination of biologically active compounds such as PIMBA, a SPECT imaging agent of breast cancer, and (-)-IBZM, a dopamine D2 receptor antagonist. The method was also modified for the radioiodination of arenes using a one-pot procedure involving the in situ generation of [(125)I]-N-iodosuccinimide followed by the silver(I)-catalyzed iodination. PMID:26795534

  15. Production of higher quality bio-oils by in-line esterification of pyrolysis vapor

    SciTech Connect

    Hilten, Roger Norris; Das, Keshav; Kastner, James R; Bibens, Brian P

    2014-12-02

    The disclosure encompasses in-line reactive condensation processes via vapor phase esterification of bio-oil to decease reactive species concentration and water content in the oily phase of a two-phase oil, thereby increasing storage stability and heating value. Esterification of the bio-oil vapor occurs via the vapor phase contact and subsequent reaction of organic acids with ethanol during condensation results in the production of water and esters. The pyrolysis oil product can have an increased ester content and an increased stability when compared to a condensed pyrolysis oil product not treated with an atomized alcohol.

  16. Impaired cholesterol esterification in primary brain cultures of the lysosomal cholesterol storage disorder (LCSD) mouse mutant

    SciTech Connect

    Patel, S.C.; Suresh, S.; Weintroub, H.; Brady, R.O.; Pentchev, P.G.

    1987-02-27

    Esterification of cholesterol was investigated in primary neuroglial cultures obtained from newborn lysosomal cholesterol storage disorder (LCSD) mouse mutants. An impairment in /sup 3/H-oleic acid incorporation into cholesteryl esters was demonstrated in cultures of homozygous LCSD brain. Primary cultures derived from other phenotypically normal pups of the carrier breeders esterified cholesterol at normal levels or at levels which were intermediary between normal and deficient indicating a phenotypic expression of the LCSD heterozygote genotype. These observations on LCSD mutant brain cells indicate that the defect in cholesterol esterification is closely related to the primary genetic defect and is expressed in neuroglial cells in culture.

  17. Pd-Catalyzed Coupling of γ-C(sp(3))-H Bonds of Oxalyl Amide-Protected Amino Acids with Heteroaryl and Aryl Iodides.

    PubMed

    Han, Jian; Zheng, Yongxiang; Wang, Chao; Zhu, Yan; Huang, Zhi-Bin; Shi, Da-Qing; Zeng, Runsheng; Zhao, Yingsheng

    2016-07-01

    Pd-catalyzed regioselective coupling of γ-C(sp(3))-H bonds of oxalyl amide-protected amino acids with heteroaryl and aryl iodides is reported. A wide variety of iodides are tolerated, giving the corresponding products in moderate to good yields. Various oxalyl amide-protected amino acids were compatible in this C-H transformation, thus representing a practical method for constructing non-natural amino acid derivatives. PMID:27286881

  18. UGT74D1 Catalyzes the Glucosylation of 2-Oxindole-3-Acetic Acid in the Auxin Metabolic Pathway in Arabidopsis

    PubMed Central

    Tanaka, Keita; Hayashi, Ken-ichiro; Natsume, Masahiro; Kamiya, Yuji; Sakakibara, Hitoshi; Kawaide, Hiroshi; Kasahara, Hiroyuki

    2014-01-01

    IAA is a naturally occurring auxin that plays a crucial role in the regulation of plant growth and development. The endogenous concentration of IAA is spatiotemporally regulated by biosynthesis, transport and its inactivation in plants. Previous studies have shown that the metabolism of IAA to 2-oxindole-3-acetic acid (OxIAA) and OxIAA-glucoside (OxIAA-Glc) may play an important role in IAA homeostasis, but the genes involved in this metabolic pathway are still unknown. In this study, we show that UGT74D1 catalyzes the glucosylation of OxIAA in Arabidopsis. By screening yeasts transformed with Arabidopsis UDP-glycosyltransferase (UGT) genes, we found that OxIAA-Glc accumulates in the culture media of yeasts expressing UGT74D1 in the presence of OxIAA. Further, we showed that UGT74D1 expressed in Escherichia coli converts OxIAA to OxIAA-Glc. The endogenous concentration of OxIAA-Glc decreased by 85% while that of OxIAA increased 2.5-fold in ugt74d1-deficient mutants, indicating the major role of UGT74D1 in OxIAA metabolism. Moreover, the induction of UGT74D1 markedly increased the level of OxIAA-Glc and loss of root gravitropism. These results indicate that UGT74D1 catalyzes a committed step in the OxIAA-dependent IAA metabolic pathway in Arabidopsis. PMID:24285754

  19. Determination of DNA adducts by combining acid-catalyzed hydrolysis and chromatographic analysis of the carcinogen-modified nucleobases.

    PubMed

    Leung, Elvis M K; Deng, Kailin; Wong, Tin-Yan; Chan, Wan

    2016-01-01

    The commonly used method of analyzing carcinogen-induced DNA adducts involves the hydrolysis of carcinogen-modified DNA samples by using a mixture of enzymes, followed by (32)P-postlabeling or liquid chromatography (LC)-based analyses of carcinogen-modified mononucleotides/nucleosides. In the present study, we report the development and application of a new approach to DNA adduct analysis by combining the H(+)/heat-catalyzed release of carcinogen-modified nucleobases and the use of LC-based methods to analyze DNA adducts. Results showed that heating the carcinogen-modified DNA samples at 70 °C for an extended period of 4 to 6 h in the presence of 0.05% HCl can efficiently induce DNA depurination, releasing the intact carcinogen-modified nucleobases for LC analyses. After optimizing the hydrolysis conditions, DNA samples with C8- and N (2) -modified 2'-deoxyguanosine, as well as N (6) -modified 2'-deoxyadenosine, were synthesized by reacting DNA with 1-nitropyrene, acetaldehyde, and aristolochic acids, respectively. These samples were then hydrolyzed, and the released nucleobase adducts were analyzed using LC-based analytical methods. Analysis results demonstrated a dose-dependent release of target DNA adducts from carcinogen-modified DNA samples, indicating that the developed H(+)/heat-catalyzed hydrolysis method was quantitative. Comparative studies with enzymatic digestion method on carcinogen-modified DNA samples revealed that the two hydrolysis methods did not yield systematically different results.

  20. Microwave-Assisted Esterification: A Discovery-Based Microscale Laboratory Experiment

    ERIC Educational Resources Information Center

    Reilly, Maureen K.; King, Ryan P.; Wagner, Alexander J.; King, Susan M.

    2014-01-01

    An undergraduate organic chemistry laboratory experiment has been developed that features a discovery-based microscale Fischer esterification utilizing a microwave reactor. Students individually synthesize a unique ester from known sets of alcohols and carboxylic acids. Each student identifies the best reaction conditions given their particular…

  1. An Esterification Kinetics Experiment that Relies on the Sense of Smell

    ERIC Educational Resources Information Center

    Bromfield-Lee, Deborah C.; Oliver-Hoyo, Maria T.

    2009-01-01

    This experiment involves an esterification synthesis to study reaction kinetics where students explore these topics utilizing the sense of smell rather than the traditional approach of using spectroscopic methods. Students study the effects of various factors including the concentration of the carboxylic acid and the amounts of the catalyst or…

  2. Comprehensive near infrared study of Jatropha oil esterification with ethanol for biodiesel production.

    PubMed

    Oliveira, Alianda Dantas de; Sá, Ananda Franco de; Pimentel, Maria Fernanda; Pacheco, José Geraldo A; Pereira, Claudete Fernandes; Larrechi, Maria Soledad

    2017-01-01

    This work presents a comprehensive near infrared study for in-line monitoring of the esterification reaction of high acid oils, such as Jatropha curcas oil, using ethanol. Parallel reactions involved in the process were carried out to select a spectral region that characterizes the evolution of the esterification reaction. Using absorbance intensities at 5176cm(-1), the conversion and kinetic behaviors of the esterification reaction were estimated. This method was applied to evaluate the influence of temperature and catalyst concentration on the estimates of initial reaction rate and ester conversion as responses to a 2(2) factorial experimental design. Employment of an alcohol/oil ratio of 16:1, catalyst concentration of 1.5% w/w, and temperatures at 65°C or 75°C, made it possible to reduce the initial acidity from 18% to 1.3% w/w, which is suitable for transesterification of high free fatty acid oils for biodiesel production. Using the proposed analytical method in the esterification reaction of raw materials with high free fatty acid content for biodiesel makes the monitoring process inexpensive, fast, simple, and practical. PMID:27415971

  3. Comprehensive near infrared study of Jatropha oil esterification with ethanol for biodiesel production.

    PubMed

    Oliveira, Alianda Dantas de; Sá, Ananda Franco de; Pimentel, Maria Fernanda; Pacheco, José Geraldo A; Pereira, Claudete Fernandes; Larrechi, Maria Soledad

    2017-01-01

    This work presents a comprehensive near infrared study for in-line monitoring of the esterification reaction of high acid oils, such as Jatropha curcas oil, using ethanol. Parallel reactions involved in the process were carried out to select a spectral region that characterizes the evolution of the esterification reaction. Using absorbance intensities at 5176cm(-1), the conversion and kinetic behaviors of the esterification reaction were estimated. This method was applied to evaluate the influence of temperature and catalyst concentration on the estimates of initial reaction rate and ester conversion as responses to a 2(2) factorial experimental design. Employment of an alcohol/oil ratio of 16:1, catalyst concentration of 1.5% w/w, and temperatures at 65°C or 75°C, made it possible to reduce the initial acidity from 18% to 1.3% w/w, which is suitable for transesterification of high free fatty acid oils for biodiesel production. Using the proposed analytical method in the esterification reaction of raw materials with high free fatty acid content for biodiesel makes the monitoring process inexpensive, fast, simple, and practical.

  4. Adsorptive control of water in esterification with immobilized enzymes: II. fixed-bed reactor behavior.

    PubMed

    Mensah, P; Gainer, J L; Carta, G

    1998-11-20

    Experimental and theoretical studies are conducted to understand the dynamic behavior of a continuous-flow fixed-bed reactor in which an esterification is catalyzed by an immobilized enzyme in an organic solvent medium. The experimental system consists of a commercial immobilized lipase preparation known as Lipozyme as the biocatalyst, with propionic acid and isoamyl alcohol (dissolved in hexane) as the reaction substrates. A complex dynamic behavior is observed experimentally as a result of the simultaneous occurrence of reaction and adsorption phenomena. Both propionic acid and water are adsorbed by the biocatalyst resulting in lower reaction rates. In addition, an excessive accumulation of water in the reactor leads to a rapid irreversible inactivation of the enzyme. A model based on previously-obtained adsorption isotherms and kinetic expressions, as well as on adsorption rate measurements obtained in this work, is used to predict the concentration and thermodynamic activity of water along the reactor length. The model successfully predicts the dynamic behavior of the reactor and shows that a maximum thermodynamic activity of water occurs at a point at some distance from the reactor entrance. A cation exchange resin in sodium form, packed in the reactor as a selective water adsorbent together with the catalyst particles, is shown to be an effective means for preventing an excessive accumulation of water formed in the reaction. Its use results in longer cycle times and greater productivity. As predicted by the model, the experimental results show that the water adsorbed on the catalyst and on the ion exchange resin can be removed with isoamyl alcohol with no apparent loss in enzyme activity.

  5. An Expeditious Synthesis of Sialic Acid Derivatives by Copper(I)-Catalyzed Stereodivergent Propargylation of Unprotected Aldoses

    PubMed Central

    2016-01-01

    We developed a copper(I)-catalyzed stereodivergent anomeric propargylation of unprotected aldoses as a facile synthetic pathway to a broad variety of sialic acid derivatives. The soft allenylcopper(I) species, catalytically generated from stable allenylboronic acid pinacolate (2), is unusually inert to protonolysis by the multiple hydroxy groups of the substrates and thereby functions as a carbon nucleophile. The key additive B(OMe)3 facilitated ring-opening of the nonelectrophilic cyclic hemiacetal forms of aldoses to the reactive aldehyde forms. The chirality of the catalyst, and not the internal stereogenic centers of substrates, predominantly controlled the stereochemistry of the propargylation step; i.e., the diastereoselectivity was switched simply by changing the catalyst chirality. This is the first nonenzyme catalyst-controlled stereodivergent C–C bond elongation at the anomeric center of unprotected aldoses, which contain multiple protic functional groups and stereogenic centers. The propargylation products can be expeditiously transformed into naturally occurring and synthetic sialic acid derivatives in a simple three-step sequence. This synthetic method, which requires no protecting groups, can be performed on a gram-scale and thus offers general and practical access to various sialic acid derivatives from unprotected aldoses. PMID:27163022

  6. Acid-catalyzed hydrolysis of lignin β-O-4 linkages in ionic liquid solvents: a computational mechanistic study.

    PubMed

    Janesko, Benjamin G

    2014-03-21

    This work presents a computational mechanistic study of the acid-catalyzed hydrolysis of lignin β-O-4 linkages in ionic liquid solvents. Model compound 2-hydroyxyethyl phenyl ether undergoes dehydration to vinyl phenyl ether followed by hydrolysis to phenol and "Hibbert's ketones". Larger model compound α-hydroxy-phenethyl phenyl ether illustrates an E1 dehydration mechanism involving resonance-stabilized carbocations. Continuum models for ionic liquid solvents indicate that solvation can significantly affect the reaction rates. The tested continuum ionic liquid solvents give similar results, and differ significantly from continuum organic solvents with comparable dielectric constants. The acidic ionic liquid cation 1-H-3-methylimidazolium has lower predicted catalytic activity than hydronium or HCl, consistent with the former's relatively small acid dissociation constant. Calculations with dispersion-corrected density functionals give similar behavior. Calculations on Lewis acidic metal chlorides used experimentally for lignin hydrolysis suggest that the metal chloride may participate in the initial dehydration. These results provide a baseline for future studies of improved hydrolysis catalysts. PMID:24509442

  7. An Expeditious Synthesis of Sialic Acid Derivatives by Copper(I)-Catalyzed Stereodivergent Propargylation of Unprotected Aldoses.

    PubMed

    Wei, Xiao-Feng; Shimizu, Yohei; Kanai, Motomu

    2016-01-27

    We developed a copper(I)-catalyzed stereodivergent anomeric propargylation of unprotected aldoses as a facile synthetic pathway to a broad variety of sialic acid derivatives. The soft allenylcopper(I) species, catalytically generated from stable allenylboronic acid pinacolate (2), is unusually inert to protonolysis by the multiple hydroxy groups of the substrates and thereby functions as a carbon nucleophile. The key additive B(OMe)3 facilitated ring-opening of the nonelectrophilic cyclic hemiacetal forms of aldoses to the reactive aldehyde forms. The chirality of the catalyst, and not the internal stereogenic centers of substrates, predominantly controlled the stereochemistry of the propargylation step; i.e., the diastereoselectivity was switched simply by changing the catalyst chirality. This is the first nonenzyme catalyst-controlled stereodivergent C-C bond elongation at the anomeric center of unprotected aldoses, which contain multiple protic functional groups and stereogenic centers. The propargylation products can be expeditiously transformed into naturally occurring and synthetic sialic acid derivatives in a simple three-step sequence. This synthetic method, which requires no protecting groups, can be performed on a gram-scale and thus offers general and practical access to various sialic acid derivatives from unprotected aldoses. PMID:27163022

  8. Direct production of biodiesel from high-acid value Jatropha oil with solid acid catalyst derived from lignin

    PubMed Central

    2011-01-01

    Background Solid acid catalyst was prepared from Kraft lignin by chemical activation with phosphoric acid, pyrolysis and sulfuric acid. This catalyst had high acid density as characterized by scanning electron microscope (SEM), energy-dispersive x-ray spectrometry (EDX) and Brunauer, Emmett, and Teller (BET) method analyses. It was further used to catalyze the esterification of oleic acid and one-step conversion of non-pretreated Jatropha oil to biodiesel. The effects of catalyst loading, reaction temperature and oil-to-methanol molar ratio, on the catalytic activity of the esterification were investigated. Results The highest catalytic activity was achieved with a 96.1% esterification rate, and the catalyst can be reused three times with little deactivation under optimized conditions. Biodiesel production from Jatropha oil was studied under such conditions. It was found that 96.3% biodiesel yield from non-pretreated Jatropha oil with high-acid value (12.7 mg KOH/g) could be achieved. Conclusions The catalyst can be easily separated for reuse. This single-step process could be a potential route for biodiesel production from high-acid value oil by simplifying the procedure and reducing costs. PMID:22145867

  9. Boronic Acid-Catalyzed, Highly Enantioselective Aza-Michael Additions of Hydroxamic Acid to Quinone Imine Ketals.

    PubMed

    Hashimoto, Takuya; Gálvez, Alberto Osuna; Maruoka, Keiji

    2015-12-30

    Boronic acid is one of the most versatile organic molecules in chemistry. Its uses include organic reactions, molecular recognition, assembly, and even medicine. While boronic acid catalysis, which utilizes an inherent catalytic property, has become an important research objective, it still lags far behind other boronic acid chemistries. Here, we report our discovery of a new boronic acid catalysis that enables the aza-Michael addition of hydroxamic acid to quinone imine ketals. By using 3-borono-BINOL as a chiral boronic acid catalyst, this reaction could be implemented in a highly enantioselective manner, paving the way to densely functionalized cyclohexanes.

  10. Laccase-catalyzed cross-linking of amino acids and peptides with dihydroxylated aromatic compounds.

    PubMed

    Mikolasch, Annett; Hahn, Veronika; Manda, Katrin; Pump, Judith; Illas, Nicole; Gördes, Dirk; Lalk, Michael; Gesell Salazar, Manuela; Hammer, Elke; Jülich, Wolf-Dieter; Rawer, Stephan; Thurow, Kerstin; Lindequist, Ulrike; Schauer, Frieder

    2010-08-01

    In order to design potential biomaterials, we investigated the laccase-catalyzed cross-linking between L-lysine or lysine-containing peptides and dihydroxylated aromatics. L-Lysine is one of the major components of naturally occurring mussel adhesive proteins (MAPs). Dihydroxylated aromatics are structurally related to 3,4-dihydroxyphenyl-L-alanine, another main component of MAPs. Mass spectrometry and nuclear magnetic resonance analyses show that the epsilon-amino group of L-lysine is able to cross-link dihydroxylated aromatics. Additional oligomer and polymer cross-linked products were obtained from di- and oligopeptides containing L-lysine. Potential applications in medicine or industry for biomaterials synthesised via the three component system consisting of the oligopeptide [Tyr-Lys]10, dihydroxylated aromatics and laccase are discussed.

  11. The Acid Hydrolysis Mechanism of Acetals Catalyzed by a Supramolecular Assembly in Basic Solution

    SciTech Connect

    Pluth, Michael D.; Bergman, Robert G.; Raymond, Kenneth N.

    2008-09-24

    A self-assembled supramolecular host catalyzes the hydrolysis of acetals in basic aqueous solution. The mechanism of hydrolysis is consistent with the Michaelis-Menten kinetic model. Further investigation of the rate limiting step of the reaction revealed a negative entropy of activation ({Delta}S{double_dagger} = -9 cal mol{sup -1}K{sup -1}) and an inverse solvent isotope effect (k(H{sub 2}O)/k(D{sub 2}O) = 0.62). These data suggest that the mechanism of hydrolysis that takes place inside the assembly proceeds through an A-2 mechanism, in contrast to the A-1 mechanism operating in the uncatalyzed reaction. Comparison of the rates of acetal hydrolysis in the assembly with the rate of the reaction of unencapsulated substrates reveals rate accelerations of up to 980 over the background reaction for the substrate diethoxymethane.

  12. Free energy surface for Brønsted acid-catalyzed glucose ring-opening in aqueous solution.

    PubMed

    Qian, Xianghong

    2013-10-01

    Car-Parrinello-based molecular dynamics coupled with metadynamics simulations were used to determine the mechanism and associated free energy surface for opening the ring structure of cyclic glucopyranose in acidic aqueous solutions. The ring-opening process is initiated by the protonation of the ring oxygen atom and the breakage of the C1-O5 bond. The barrier for this process is about 25 kcal/mol, in good agreement with experimental measurements. Moreover, the glucose cyclic conformation is found to be more stable than the open chain form. The barrier for proton-catalyzed ring-opening in aqueous solution appears to be largely solvent induced due to the high affinity of water molecules for protons. PMID:23992399

  13. Depolymerization of crystalline cellulose catalyzed by acidic ionic liquids grafted onto sponge-like nanoporous polymers.

    PubMed

    Liu, Fujian; Kamat, Ranjan K; Noshadi, Iman; Peck, Daniel; Parnas, Richard S; Zheng, Anmin; Qi, Chenze; Lin, Yao

    2013-10-01

    The acidic ionic liquid (IL) functionalized polymer (PDVB-SO3H-[C3vim][SO3CF3]) possesses abundant nanoporous structures, strong acid strength and unique capability for deconstruction of crystalline cellulose into sugars in ILs. The polymer shows much improved catalytic activities in comparison with mineral acids, homogeneous acidic ionic liquids and the acidic resins such as Amberlyst 15. The enhanced catalytic activity found in the polymer is attributed to synergistic effects between the strongly acidic group and the ILs grafted onto the polymer, which by itself is capable of breaking down the crystalline structures of cellulose. This study may help develop cost-effective and green routes for conversion of biomass to fuels. PMID:23958800

  14. Palladium-catalyzed cross-coupling of sterically demanding boronic acids with α-bromocarbonyl compounds.

    PubMed

    Zimmermann, Bettina; Dzik, Wojciech I; Himmler, Thomas; Goossen, Lukas J

    2011-10-01

    A catalyst system generated in situ from Pd(dba)(2) and tri(o-tolyl)phosphine mediates the coupling of arylboronic acids with alkyl α-bromoacetates under formation of arylacetic acid esters at unprecedented low loadings. The new protocol, which involves potassium fluoride as the base and catalytic amounts of benzyltriethylammonium bromide as a phase transfer catalyst, is uniquely effective for the synthesis of sterically demanding arylacetic acid derivatives.

  15. Efficient ytterbium triflate catalyzed microwave-assisted synthesis of 3-acylacrylic acid building blocks.

    PubMed

    Tolstoluzhsky, Nikita V; Gorobets, Nikolay Yu; Kolos, Nadezhda N; Desenko, Sergey M

    2008-01-01

    The derivatives of 4-(hetero)aryl-4-oxobut-2-enoic acid are useful as building blocks in the synthesis of biologically active compounds. An efficient general protocol for the synthesis of these building blocks was developed. This method combines microwave assistance and ytterbium triflate catalyst and allows the fast preparation of the target acids starting from different (hetero)aromatic ketones and glyoxylic acid monohydrate giving pure products in 52-75% isolated yields.

  16. Preparation of a sulfonated carbonaceous material from lignosulfonate and its usefulness as an esterification catalyst.

    PubMed

    Lee, Duckhee

    2013-07-10

    Sulfonated carbonaceous material useful as a solid acid catalyst was prepared from lignosulfonate, a waste of the paper-making industry sulfite pulping process, and characterized by 13C-NMR, FT-IR, TGA, SEM and elemental analysis, etc. The sulfonic acid group density and total density of all acid groups in the sulfonated carbonaceous material was determined by titration to be 1.24 mmol/g and 5.90 mmol/g, respectively. Its catalytic activity in the esterification of cyclohexanecarboxylic acid with anhydrous ethanol was shown to be comparable to that of the ionic exchange resin Amberlyst-15, when they were used in the same amount. In the meantime, the sulfonic acid group was found to be leached out by 26%-29% after it was exposed to hot water (95 °C) for 5 h. The catalytic usefulness of the prepared carbonaceous material was investigated by performing esterifications.

  17. Isoprene Epoxydiols as Precursors to Secondary Organic Aerosol Formation: Acid-Catalyzed Reactive Uptake Studies with Authentic Compounds

    PubMed Central

    Lin, Ying-Hsuan; Zhang, Zhenfa; Docherty, Kenneth S.; Zhang, Haofei; Budisulistiorini, Sri Hapsari; Rubitschun, Caitlin L.; Shaw, Stephanie L.; Knipping, Eladio M.; Edgerton, Eric S.; Kleindienst, Tadeusz E.; Gold, Avram; Surratt, Jason D.

    2011-01-01

    Isoprene epoxydiols (IEPOX), formed from the photooxidation of isoprene under low-NOx conditions, have recently been proposed as precursors of secondary organic aerosol (SOA) on the basis of mass spectrometric evidence. In the present study, IEPOX isomers were synthesized in high purity (> 99%) to investigate their potential to form SOA via reactive uptake in a series of controlled dark chamber studies followed by reaction product analyses. IEPOX-derived SOA was substantially observed only in the presence of acidic aerosols, with conservative lower-bound yields of 4.7–6.4% for β-IEPOX and 3.4–5.5% for δ-IEPOX, providing direct evidence for IEPOX isomers as precursors to isoprene SOA. These chamber studies demonstrate that IEPOX uptake explains the formation of known isoprene SOA tracers found in ambient aerosols, including 2-methyltetrols, C5-alkene triols, dimers, and IEPOX-derived organosulfates. Additionally, we show reactive uptake on the acidified sulfate aerosols supports a previously unreported acid-catalyzed intramolecular rearrangement of IEPOX to cis- and trans-3-methyltetrahydrofuran-3,4-diols (3-MeTHF-3,4-diols) in the particle phase. Analysis of these novel tracer compounds by aerosol mass spectrometry (AMS) suggests that they contribute to a unique factor resolved from positive matrix factorization (PMF) of AMS organic aerosol spectra collected from low-NOx, isoprene-dominated regions influenced by the presence of acidic aerosols. PMID:22103348

  18. Acceleration of Enantioselective Cycloadditions Catalyzed by Second-Generation Chiral Oxazaborolidinium Triflimidates by Biscoordinating Lewis Acids.

    PubMed

    Thirupathi, Barla; Breitler, Simon; Mahender Reddy, Karla; Corey, E J

    2016-08-31

    The activation of second-generation fluorinated oxazaborolidines by the strong acid triflimide (Tf2NH) in CH2Cl2 solution leads to highly active chiral Lewis acids that are very effective catalysts for (4 + 2) cycloaddition. We report herein that this catalytic activity can be further enhanced by the use of Tf2NH in combination with the biscoordinating Lewis acid TiCl4 or SnCl4 as a coactivator. The effective increase in acidity of an exceedingly strong protic acid is greater for biscoordinating TiCl4 and SnCl4 than for monocoordinating salts, even the strong Lewis acids AlBr3 and BBr3 in CH2Cl2 or CH2Cl2/toluene. The increase in the effective acidity of Tf2NH can be understood in terms of a stabilized cyclic anionic complex of Tf2N(-) and TiCl4, which implies a broader utility than that described here. The utility of Tf2NH-TiCl4 activation of fluorinated oxazaborolidines is documented by examples including the first enantioselective (4 + 2) cycloaddition to α,β-unsaturated acid chlorides.

  19. Cationic Pd(II)-Catalyzed Cyclization of N-Tosyl-aniline Tethered Allenyl Aldehydes with Arylboronic Acids: Diastereo- and Enantioselective Synthesis of Tetrahydroquinoline Derivatives.

    PubMed

    Zhang, Xiaojuan; Han, Xiuling; Lu, Xiyan

    2015-08-01

    An efficient cyclization of N-tosyl-aniline tethered allenyl aldehydes and arylboronic acids catalyzed by cationic palladium complex is developed. This annulation reaction provides a convenient process for the synthesis of 3,4-cis-1,2,3,4-tetrahydroquinoline derivatives in high yields with excellent diastereoselectivity and enantioselectivity.

  20. C8-Selective Acylation of Quinoline N-Oxides with α-Oxocarboxylic Acids via Palladium-Catalyzed Regioselective C-H Bond Activation.

    PubMed

    Chen, Xiaopei; Cui, Xiuling; Wu, Yangjie

    2016-08-01

    A facile and efficient protocol for palladium-catalyzed C8-selective acylation of quinoline N-oxides with α-oxocarboxylic acids has been developed. In this approach, N-oxide was utilized as a stepping stone for the remote C-H functionalization. The reactions proceeded efficiently under mild reaction conditions with excellent regioselectivity and broad functional group tolerance. PMID:27441527

  1. A Convenient Palladium-Catalyzed Carbonylative Synthesis of Benzofuran-2(3 H)-ones with Formic Acid as the CO Source.

    PubMed

    Qi, Xinxin; Li, Hao-Peng; Wu, Xiao-Feng

    2016-09-01

    A general and convenient palladium-catalyzed carbonylation procedure for the synthesis of benzofuran-2(3 H)-ones from phenols and aldehydes has been developed. With formic acid as the CO source, a variety of benzofuran-2(3 H)-ones were obtained in moderate to good yields. PMID:27539230

  2. Chloroperoxidase-catalyzed enantioselective oxidation of methyl phenyl sulfide with dihydroxyfumaric acid/oxygen or ascorbic acid/oxygen as oxidants.

    PubMed

    Pasta; Carrea; Monzani; Gaggero; Colonna

    1999-02-01

    The chloroperoxidase catalyzed oxidation of methyl phenyl sulfide to (R)-methyl phenyl sulfoxide was investigated, both in batch and membrane reactors, using as oxidant H2O2, or O2 in the presence of either dihydroxyfumaric acid or ascorbic acid. The effects of pH and nature and concentration of the oxidants on the selectivity, stability, and productivity of the enzyme were evaluated. The highest selectivity was displayed by ascorbic acid/O2, even though the activity of chloroperoxidase with this system was lower than that obtained with the others. When the reaction was carried out in a membrane reactor, it was possible to reuse the enzyme for several conversion cycles. The results obtained with ascorbic acid/O2 and dihydroxyfumaric acid/O2 as oxidants do not seem to be compatible with either a mechanism involving hydroxyl radicals as the active species or with the hypothesis that oxidation occurs through the initial formation of H2O2. Copyright 1999 John Wiley & Sons, Inc.

  3. Acid-catalyzed steam pretreatment of lodgepole pine and subsequent enzymatic hydrolysis and fermentation to ethanol.

    PubMed

    Ewanick, Shannon M; Bura, Renata; Saddler, John N

    2007-11-01

    Utilization of ethanol produced from biomass has the potential to offset the use of gasoline and reduce CO(2) emissions. This could reduce the effects of global warming, one of which is the current outbreak of epidemic proportions of the mountain pine beetle (MPB) in British Columbia (BC), Canada. The result of this is increasing volumes of dead lodgepole pine with increasingly limited commercial uses. Bioconversion of lodgepole pine to ethanol using SO(2)-catalyzed steam explosion was investigated. The optimum pretreatment condition for this feedstock was determined to be 200 degrees C, 5 min, and 4% SO(2) (w/w). Simultaneous saccharification and fermentation (SSF) of this material provided an overall ethanol yield of 77% of the theoretical yield from raw material based on starting glucan, mannan, and galactan, which corresponds to 244 g ethanol/kg raw material within 30 h. Three conditions representing low (L), medium (M), and high (H) severity were also applied to healthy lodgepole pine. Although the M severity conditions of 200 degrees C, 5 min, and 4% SO(2) were sufficiently robust to pretreat healthy wood, the substrate produced from beetle-killed (BK) wood provided consistently higher ethanol yields after SSF than the other substrates tested. BK lodgepole pine appears to be an excellent candidate for efficient and productive bioconversion to ethanol.

  4. Envisioning an enzymatic Diels-Alder reaction by in situ acid-base catalyzed diene generation.

    PubMed

    Linder, Mats; Johansson, Adam Johannes; Manta, Bianca; Olsson, Philip; Brinck, Tore

    2012-06-01

    We present and evaluate a new and potentially efficient route for enzyme-mediated Diels-Alder reactions, utilizing general acid-base catalysis. The viability of employing the active site of ketosteroid isomerase is demonstrated.

  5. Enantioselective synthesis of benzazepinoindoles bearing trifluoromethylated quaternary stereocenters catalyzed by chiral spirocyclic phosphoric acids.

    PubMed

    Li, Xuejian; Chen, Di; Gu, Haorui; Lin, Xufeng

    2014-07-18

    The first highly enantioselective iso-Pictet-Spengler reaction of C-2-linked o-aminobenzylindoles with trifluoromethyl ketones was developed using chiral spirocyclic phosphoric acids as organocatalysts, which afforded optically active benzazepinoindoles bearing trifluoromethylated quaternary stereocenters. PMID:24890313

  6. Lewis base activation of Lewis acids: development of a Lewis base catalyzed selenolactonization.

    PubMed

    Denmark, Scott E; Collins, William R

    2007-09-13

    The concept of Lewis base activation of Lewis acids has been applied to the selenolactonization reaction. Through the use of substoichiometric amounts of Lewis bases with "soft" donor atoms (S, Se, P) significant rate enhancements over the background reaction are seen. Preliminary mechanistic investigations have revealed the resting state of the catalyst as well as the significance of a weak Brønsted acid promoter.

  7. Isolation of cellulose from rice straw and its conversion into cellulose acetate catalyzed by phosphotungstic acid.

    PubMed

    Fan, Guozhi; Wang, Min; Liao, Chongjing; Fang, Tao; Li, Jianfen; Zhou, Ronghui

    2013-04-15

    Cellulose was isolated from rice straw by pretreatment with dilute alkaline and acid solutions successively, and it was further transferred into cellulose acetate in the presence of acetic anhydride and phosphotungstic acid (H3PW12O40·6H2O). The removal of hemicellulose and lignin was affected by the concentration of KOH and the immersion time in acetic acid solution, and 83wt.% content of cellulose in the treated rice straw was obtained after pretreatment with 4% KOH and immersion in acetic acid for 5h. Phosphotungstic acid was found to be an effective catalyst for the acetylation of the cellulose derived from rice straw. The degree of substitution (DS) values revealed a significant effect for the solubility of cellulose acetate, and the acetone-soluble cellulose acetate with DS values around 2.2 can be obtained by changing the amount of phosphotungstic acid and the time of acetylation. Both the structure of cellulose separated from rice straw and cellulose acetate were confirmed by FTIR and XRD.

  8. ATP-binding cassette transporters and sterol O-acyltransferases interact at membrane microdomains to modulate sterol uptake and esterification.

    PubMed

    Gulati, Sonia; Balderes, Dina; Kim, Christine; Guo, Zhongmin A; Wilcox, Lisa; Area-Gomez, Estela; Snider, Jamie; Wolinski, Heimo; Stagljar, Igor; Granato, Juliana T; Ruggles, Kelly V; DeGiorgis, Joseph A; Kohlwein, Sepp D; Schon, Eric A; Sturley, Stephen L

    2015-11-01

    A key component of eukaryotic lipid homeostasis is the esterification of sterols with fatty acids by sterol O-acyltransferases (SOATs). The esterification reactions are allosterically activated by their sterol substrates, the majority of which accumulate at the plasma membrane. We demonstrate that in yeast, sterol transport from the plasma membrane to the site of esterification is associated with the physical interaction of the major SOAT, acyl-coenzyme A:cholesterol acyltransferase (ACAT)-related enzyme (Are)2p, with 2 plasma membrane ATP-binding cassette (ABC) transporters: Aus1p and Pdr11p. Are2p, Aus1p, and Pdr11p, unlike the minor acyltransferase, Are1p, colocalize to sterol and sphingolipid-enriched, detergent-resistant microdomains (DRMs). Deletion of either ABC transporter results in Are2p relocalization to detergent-soluble membrane domains and a significant decrease (53-36%) in esterification of exogenous sterol. Similarly, in murine tissues, the SOAT1/Acat1 enzyme and activity localize to DRMs. This subcellular localization is diminished upon deletion of murine ABC transporters, such as Abcg1, which itself is DRM associated. We propose that the close proximity of sterol esterification and transport proteins to each other combined with their residence in lipid-enriched membrane microdomains facilitates rapid, high-capacity sterol transport and esterification, obviating any requirement for soluble intermediary proteins.

  9. How Acid-Catalyzed Decarboxylation of 2,4-Dimethoxybenzoic Acid Avoids Formation of Protonated CO2.

    PubMed

    Howe, Graeme W; Vandersteen, Adelle A; Kluger, Ronald

    2016-06-22

    The decarboxylation of 2,4-dimethoxybenzoic acid (1) is accelerated in acidic solutions. The rate of reaction depends upon solution acidity in a manner that is consistent with the formation of the conjugate acid of 1 (RCO2H2(+)), with its higher energy ring-protonated tautomer allowing the requisite C-C bond cleavage. However, this would produce the conjugate acid of CO2, a species that would be too energetic to form. Considerations of mechanisms that fit the observed rate law were supplemented with DFT calculations. Those results indicate that the lowest energy pathway from the ring-protonated reactive intermediate involves early proton transfer from the carboxyl group to water along with C-C bond cleavage, producing 1,3-dimethoxybenzene and CO2 directly. PMID:27241436

  10. Fast esterification of spent grain for enhanced heavy metal ions adsorption.

    PubMed

    Li, Qingzhu; Chai, Liyuan; Wang, Qingwei; Yang, Zhihui; Yan, Huxiang; Wang, Yunyan

    2010-05-01

    This work describes a novel method for fast esterification of spent grain to enhance its cationic adsorption capacity. The esterification of spent grain with citric acid was achieved by using sodium hypophosphite monohydrate (NaH(2)PO(2).H(2)O) as a catalyst in N,N-dimethylformamide (DMF). Fourier transform infrared (FTIR) spectroscopic analysis revealed the formation of ester groups after esterification, demonstrating that spent grain was successfully esterified with citric acid. The adsorption capacity of esterified spent grain (ESG) for each metal ion was greatly improved as compared with that of raw spent grain (RSG). Typically, Pb(2+) adsorption capacity increased from 125.84mg g(-1) of RSG to 293.30mg g(-1) of ESG. This increase can be attributed to both the formation of ester linkage and the grafting of carboxyl groups on spent grain. The results suggest that a fast process for esterification of spent grain has been realized and ESG has strong ability to adsorb heavy metal ions.

  11. Novel Dextranase Catalyzing Cycloisomaltooligosaccharide Formation and Identification of Catalytic Amino Acids and Their Functions Using Chemical Rescue Approach*

    PubMed Central

    Kim, Young-Min; Kiso, Yoshiaki; Muraki, Tomoe; Kang, Min-Sun; Nakai, Hiroyuki; Saburi, Wataru; Lang, Weeranuch; Kang, Hee-Kwon; Okuyama, Masayuki; Mori, Haruhide; Suzuki, Ryuichiro; Funane, Kazumi; Suzuki, Nobuhiro; Momma, Mitsuru; Fujimoto, Zui; Oguma, Tetsuya; Kobayashi, Mikihiko; Kim, Doman; Kimura, Atsuo

    2012-01-01

    A novel endodextranase from Paenibacillus sp. (Paenibacillus sp. dextranase; PsDex) was found to mainly produce isomaltotetraose and small amounts of cycloisomaltooligosaccharides (CIs) with a degree of polymerization of 7–14 from dextran. The 1,696-amino acid sequence belonging to the glycosyl hydrolase family 66 (GH-66) has a long insertion (632 residues; Thr451–Val1082), a portion of which shares identity (35% at Ala39–Ser1304 of PsDex) with Pro32–Ala755 of CI glucanotransferase (CITase), a GH-66 enzyme that catalyzes the formation of CIs from dextran. This homologous sequence (Val837–Met932 for PsDex and Tyr404–Tyr492 for CITase), similar to carbohydrate-binding module 35, was not found in other endodextranases (Dexs) devoid of CITase activity. These results support the classification of GH-66 enzymes into three types: (i) Dex showing only dextranolytic activity, (ii) Dex catalyzing hydrolysis with low cyclization activity, and (iii) CITase showing CI-forming activity with low dextranolytic activity. The fact that a C-terminal truncated enzyme (having Ala39–Ser1304) has 50% wild-type PsDex activity indicates that the C-terminal 392 residues are not involved in hydrolysis. GH-66 enzymes possess four conserved acidic residues (Asp189, Asp340, Glu412, and Asp1254 of PsDex) of catalytic candidates. Their amide mutants decreased activity (11,500 to 140,000 times), and D1254N had 36% activity. A chemical rescue approach was applied to D189A, D340G, and E412Q using α-isomaltotetraosyl fluoride with NaN3. D340G or E412Q formed a β- or α-isomaltotetraosyl azide, respectively, strongly indicating Asp340 and Glu412 as a nucleophile and acid/base catalyst, respectively. Interestingly, D189A synthesized small sized dextran from α-isomaltotetraosyl fluoride in the presence of NaN3. PMID:22461618

  12. Acid-catalyzed liquefaction of bagasse in the presence of polyhydric alcohol.

    PubMed

    Zhang, Hairong; Luo, Jun; Li, Yingying; Guo, Haijun; Xiong, Lian; Chen, Xinde

    2013-08-01

    Bagasse was subjected to a liquefaction process with polyethylene glycol/glycerol using sulfuric acid as catalyst. The effects of various liquefaction conditions, such as reaction time, liquefaction temperature, catalyst content, and liquid ratio (liquefaction solvents/bagasse), on the liquefied residue (LR) content and hydroxyl and acid numbers of liquefied products were investigated. The preferred liquefaction condition of bagasse was determined through orthogonal experiments. The results showed that the catalyst content and reaction time have a greater influence than liquid ratio and liquefaction temperature on the percentage of LR. The hydroxyl and acid numbers of the liquefied products were influenced by many factors, including liquefaction temperature, reaction time, acid content, and liquid ratio. The hydroxyl number of liquefied products decreased as the liquefaction reaction progressed, but the acid number of liquefied products increased. Based on the obtained data, the kinetics for liquefaction was modeled using the first-order reaction rate law and the apparent activation energy for the liquefaction of bagasse was estimated to be 38.30 kJ mol(-1).

  13. The Aerobic Oxidation of Bromide to Dibromine Catalyzed by Homogeneous Oxidation Catalysts and Initiated by Nitrate in Acetic Acid

    SciTech Connect

    Partenheimer, Walt; Fulton, John L.; Sorensen, Christina M.; Pham, Van Thai; Chen, Yongsheng

    2014-06-01

    A small amount of nitrate, ~0.002 molal, initiates the Co/Mn catalyzed aerobic oxidation of bromide compounds (HBr,NaBr,LiBr) to dibromine in acetic acid at room temperature. At temperatures 40oC or less , the reaction is autocatalytic. Co(II) and Mn(II) themselves and mixed with ionic bromide are known homogeneous oxidation catalysts. The reaction was discovered serendipitously when a Co/Br and Co/Mn/Br catalyst solution was prepared for the aerobic oxidation of methyaromatic compounds and the Co acetate contained a small amount of impurity i.e. nitrate. The reaction was characterized by IR, UV-VIS, MALDI and EXAFS spectroscopies and the coordination chemistry is described. The reaction is inhibited by water and its rate changed by pH. The change in these variables, as well as others, are identical to those observed during homogeneous, aerobic oxidation of akylaromatics. A mechanism is proposed. Accidental addition of a small amount of nitrate compound into a Co/Mn/Br/acetic acid mixture in a large, commercial feedtank is potentially dangerous.

  14. Base-free non-noble-metal-catalyzed hydrogen generation from formic acid: scope and mechanistic insights.

    PubMed

    Mellmann, Dörthe; Barsch, Enrico; Bauer, Matthias; Grabow, Kathleen; Boddien, Albert; Kammer, Anja; Sponholz, Peter; Bentrup, Ursula; Jackstell, Ralf; Junge, Henrik; Laurenczy, Gábor; Ludwig, Ralf; Beller, Matthias

    2014-10-13

    The iron-catalyzed dehydrogenation of formic acid has been studied both experimentally and mechanistically. The most active catalysts were generated in situ from cationic Fe(II) /Fe(III) precursors and tris[2-(diphenylphosphino)ethyl]phosphine (1, PP3 ). In contrast to most known noble-metal catalysts used for this transformation, no additional base was necessary. The activity of the iron catalyst depended highly on the solvent used, the presence of halide ions, the water content, and the ligand-to-metal ratio. The optimal catalytic performance was achieved by using [FeH(PP3 )]BF4 /PP3 in propylene carbonate in the presence of traces of water. With the exception of fluoride, the presence of halide ions in solution inhibited the catalytic activity. IR, Raman, UV/Vis, and EXAFS/XANES analyses gave detailed insights into the mechanism of hydrogen generation from formic acid at low temperature, supported by DFT calculations. In situ transmission FTIR measurements revealed the formation of an active iron formate species by the band observed at 1543 cm(-1) , which could be correlated with the evolution of gas. This active species was deactivated in the presence of chloride ions due to the formation of a chloro species (UV/Vis, Raman, IR, and XAS). In addition, XAS measurements demonstrated the importance of the solvent for the coordination of the PP3 ligand. PMID:25196789

  15. Base-free non-noble-metal-catalyzed hydrogen generation from formic acid: scope and mechanistic insights.

    PubMed

    Mellmann, Dörthe; Barsch, Enrico; Bauer, Matthias; Grabow, Kathleen; Boddien, Albert; Kammer, Anja; Sponholz, Peter; Bentrup, Ursula; Jackstell, Ralf; Junge, Henrik; Laurenczy, Gábor; Ludwig, Ralf; Beller, Matthias

    2014-10-13

    The iron-catalyzed dehydrogenation of formic acid has been studied both experimentally and mechanistically. The most active catalysts were generated in situ from cationic Fe(II) /Fe(III) precursors and tris[2-(diphenylphosphino)ethyl]phosphine (1, PP3 ). In contrast to most known noble-metal catalysts used for this transformation, no additional base was necessary. The activity of the iron catalyst depended highly on the solvent used, the presence of halide ions, the water content, and the ligand-to-metal ratio. The optimal catalytic performance was achieved by using [FeH(PP3 )]BF4 /PP3 in propylene carbonate in the presence of traces of water. With the exception of fluoride, the presence of halide ions in solution inhibited the catalytic activity. IR, Raman, UV/Vis, and EXAFS/XANES analyses gave detailed insights into the mechanism of hydrogen generation from formic acid at low temperature, supported by DFT calculations. In situ transmission FTIR measurements revealed the formation of an active iron formate species by the band observed at 1543 cm(-1) , which could be correlated with the evolution of gas. This active species was deactivated in the presence of chloride ions due to the formation of a chloro species (UV/Vis, Raman, IR, and XAS). In addition, XAS measurements demonstrated the importance of the solvent for the coordination of the PP3 ligand.

  16. Synthesis of ascorbyl oleate by transesterification of olive oil with ascorbic acid in polar organic media catalyzed by immobilized lipases.

    PubMed

    Moreno-Perez, Sonia; Filice, Marco; Guisan, Jose M; Fernandez-Lorente, Gloria

    2013-09-01

    The reaction of transesterification between oils (e.g., olive oil) and ascorbic acid in polar anhydrous media (e.g., tert-amyl alcohol) catalyzed by immobilized lipases for the preparation of natural liposoluble antioxidants (e.g., ascorbyl oleate) was studied. Three commercial lipases were tested: Candida antarctica B lipase (CALB), Thermomyces lanuginosus lipase (TLL) and Rhizomucor miehei lipase (RML). Each lipase was immobilized by three different protocols: hydrophobic adsorption, anionic exchange and multipoint covalent attachment. The highest synthetic yields were obtained with CALB adsorbed on hydrophobic supports (e.g., the commercial derivative Novozym 435). The rates and yields of the synthesis of ascorbyl oleate were higher when using the solvent dried with molecular sieves, at high temperatures (e.g. 45°C) and with a small excess of oil (2 mol of oil per mol of ascorbic acid). The coating of CALB derivatives with polyethyleneimine (PEI) improved its catalytic behavior and allowed the achievement of yields of up to 80% of ascorbyl oleate in less than 24h. CALB adsorbed on a hydrophobic support and coated with PEI was 2-fold more stable than a non-coated derivative and one hundred-fold more stable than the best TLL derivative. The best CALB derivative exhibited a half-life of 3 days at 75°C in fully anhydrous media, and this derivative maintained full activity after 28 days at 45°C in dried tert-amyl alcohol.

  17. Bio-based nitriles from the heterogeneously catalyzed oxidative decarboxylation of amino acids.

    PubMed

    Claes, Laurens; Matthessen, Roman; Rombouts, Ine; Stassen, Ivo; De Baerdemaeker, Trees; Depla, Diederik; Delcour, Jan A; Lagrain, Bert; De Vos, Dirk E

    2015-01-01

    The oxidative decarboxylation of amino acids to nitriles was achieved in aqueous solution by in situ halide oxidation using catalytic amounts of tungstate exchanged on a [Ni,Al] layered double hydroxide (LDH), NH4 Br, and H2 O2 as the terminal oxidant. Both halide oxidation and oxidative decarboxylation were facilitated by proximity effects between the reactants and the LDH catalyst. A wide range of amino acids was converted with high yields, often >90 %. The nitrile selectivity was excellent, and the system is compatible with amide, alcohol, and in particular carboxylic acid, amine, and guanidine functional groups after appropriate neutralization. This heterogeneous catalytic system was applied successfully to convert a protein-rich byproduct from the starch industry into useful bio-based N-containing chemicals.

  18. Phenylalanine ammonia lyase catalyzed synthesis of amino acids by an MIO-cofactor independent pathway.

    PubMed

    Lovelock, Sarah L; Lloyd, Richard C; Turner, Nicholas J

    2014-04-25

    Phenylalanine ammonia lyases (PALs) belong to a family of 4-methylideneimidazole-5-one (MIO) cofactor dependent enzymes which are responsible for the conversion of L-phenylalanine into trans-cinnamic acid in eukaryotic and prokaryotic organisms. Under conditions of high ammonia concentration, this deamination reaction is reversible and hence there is considerable interest in the development of PALs as biocatalysts for the enantioselective synthesis of non-natural amino acids. Herein the discovery of a previously unobserved competing MIO-independent reaction pathway, which proceeds in a non-stereoselective manner and results in the generation of both L- and D-phenylalanine derivatives, is described. The mechanism of the MIO-independent pathway is explored through isotopic-labeling studies and mutagenesis of key active-site residues. The results obtained are consistent with amino acid deamination occurring by a stepwise E1 cB elimination mechanism.

  19. Selenium Catalyzed Oxidation of Aldehydes: Green Synthesis of Carboxylic Acids and Esters.

    PubMed

    Sancineto, Luca; Tidei, Caterina; Bagnoli, Luana; Marini, Francesca; Lenardão, Eder J; Santi, Claudio

    2015-01-01

    The stoichiometric use of hydrogen peroxide in the presence of a selenium-containing catalyst in water is here reported as a new ecofriendly protocol for the synthesis of variously functionalized carboxylic acids and esters. The method affords the desired products in good to excellent yields under very mild conditions starting directly from commercially available aldehydes. Using benzaldehyde as a prototype the gram scale synthesis of benzoic acid is described, in which the aqueous medium and the catalyst could be recycled at last five times while achieving an 87% overall yield.

  20. Silver-Catalyzed Decarboxylative Radical Azidation of Aliphatic Carboxylic Acids in Aqueous Solution.

    PubMed

    Liu, Chao; Wang, Xiaoqing; Li, Zhaodong; Cui, Lei; Li, Chaozhong

    2015-08-12

    We report herein an efficient and general method for the decarboxylative azidation of aliphatic carboxylic acids. Thus, with AgNO3 as the catalyst and K2S2O8 as the oxidant, the reactions of various aliphatic carboxylic acids with tosyl azide or pyridine-3-sulfonyl azide in aqueous CH3CN solution afforded the corresponding alkyl azides under mild conditions. A broad substrate scope and wide functional group compatibility were observed. A radical mechanism is proposed for this site-specific azidation.

  1. Cu-Catalyzed Cyanation of Arylboronic Acids with Acetonitrile: A Dual Role of TEMPO.

    PubMed

    Zhu, Yamin; Li, Linyi; Shen, Zengming

    2015-09-14

    The cyanation of arylboronic acids by using acetonitrile as the "CN" source has been achieved under a Cu(cat.)/TEMPO system (TEMPO=2,2,6,6-tetramethylpiperidine N-oxide). The broad substrate scope includes a variety of electron-rich and electron-poor arylboronic acids, which react well to give the cyanated products in high to excellent yields. Mechanistic studies reveal that TEMPO-CH2 CN, generated in situ, is an active cyanating reagent, and shows high reactivity for the formation of the CN(-) moiety. Moreover, TEMPO acts as a cheap oxidant to enable the reaction to be catalytic in copper.

  2. Serum opacity factor enhances HDL-mediated cholesterol efflux, esterification and anti inflammatory effects.

    PubMed

    Tchoua, Urbain; Rosales, Corina; Tang, Daming; Gillard, Baiba K; Vaughan, Ashley; Lin, Hu Yu; Courtney, Harry S; Pownall, Henry J

    2010-12-01

    Serum opacity factor (SOF) is a streptococcal protein that disrupts the structure of human high density lipoproteins (HDL) releasing lipid-free apo A-I while forming a large cholesteryl ester-rich particle and a small neo HDL. Given its low cholesterol and high phospholipid contents, we tested the hypotheses that neo HDL is a better substrate for cholesterol esterification via lecithin:cholesterol acyltransferase (LCAT), better than HDL as an acceptor of THP-1 macrophage cholesterol efflux, and improves reduction of oxidized LDL-induced production of inflammatory markers. We observed that both cholesterol efflux and esterification were improved by recombinant (r)SOF treatment of whole plasma and that the underlying cause of the improved cholesterol esterification in plasma and macrophage cholesterol efflux to rSOF-treated plasma was due to the rSOF-mediated conversion of HDL to neo HDL. Moreover, the reduction of secretion of TNF-α and IL-6 by THP-1 cells by neo HDL was twice that of HDL. Studies in BHK cells overexpressing cholesterol transporters showed that efflux to neo HDL occurred primarily via ABCA1 not ABCG1. Thus, rSOF improves two steps in reverse cholesterol transport with a concomitant reduction in the release of macrophage markers of inflammation. We conclude that rSOF catalyzes a novel reaction that might be developed as a new therapy that prevents or reverses atherosclerosis via improved reverse cholesterol transport.

  3. Chiral Brønsted Acid Catalyzed Enantioselective Phosphonylation of Allylamine via Oxidative Dehydrogenation Coupling.

    PubMed

    Cheng, Ming-Xing; Ma, Ran-Song; Yang, Qiang; Yang, Shang-Dong

    2016-07-01

    A new strategy for the synthesis of chiral α-amino phosphonates by enantioselective C-H phosphonylation of allylamine with phosphite in the presence of a chiral Brønsted acid catalyst has been developed. This protocol successfully integrates direct C-H oxidation with asymmetric phosphonylation and exhibits high enantioselectivity. PMID:27331612

  4. POLYSTYRENE SULFONIC ACID CATALYZED GREENER SYNTHESIS OF HYDRAZONES IN AQUEOUS MEDIUM USING MICROWAVES

    EPA Science Inventory

    An environmentally benign aqueous protocol for the synthesis of cyclic, bi-cyclic, and heterocyclic hydrazones using polystyrene sulfonic acid (PSSA) as a catalyst has been developed; the simple reaction proceeds efficiently in water in the absence of any organic solvent under mi...

  5. Copper-catalyzed Chan-Lam coupling between sulfonyl azides and boronic acids at room temperature.

    PubMed

    Moon, Soo-Yeon; Nam, Jungsoo; Rathwell, Kris; Kim, Won-Suk

    2014-01-17

    A mild and efficient method for the synthesis of N-arylsulfonamides in the presence of 10 mol % of CuCl is demonstrated. The reaction proceeds readily at room temperature in an open flask using a variety of sulfonyl azides and boronic acids without any base, ligand, or additive.

  6. Lewis base additives improve the zeolite ferrierite-catalyzed synthesis of isostearic acid

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Isostearic acid (IA) is of interest for industrial purposes especially in the area of biolubricants, such as cosmetics and slip additives for polyolefin and related copolymer films. This study was designed to develop a zeolitic catalysis process for IA production through isomerization of fatty aci...

  7. Nonmetal catalyzed insertion reactions of diazocarbonyls to acid derivatives in fluorinated alcohols.

    PubMed

    Dumitrescu, Lidia; Azzouzi-Zriba, Kaouther; Bonnet-Delpon, Danièle; Crousse, Benoit

    2011-02-18

    The insertion reaction of diazocarbonyls to acids could be performed smoothly in fluorinated alcohols in the absence of metal catalyst. This new procedure allowed the chemoselective preparation of various functionalized compounds such as acyloxyesters, depsipeptides, and sulfonate, phosphonate, or boronate derivatives.

  8. ESTIMATION OF PHOSPHATE ESTER HYDROLYSIS RATE CONSTANTS. II. ACID AND GENERAL BASE CATALYZED HYDROLYSIS

    EPA Science Inventory

    SPARC (SPARC Performs Automated Reasoning in Chemistry) chemical reactivity models were extended to calculate acid and neutral hydrolysis rate constants of phosphate esters in water. The rate is calculated from the energy difference between the initial and transition states of a ...

  9. Copper-catalyzed Chan-Lam coupling between sulfonyl azides and boronic acids at room temperature.

    PubMed

    Moon, Soo-Yeon; Nam, Jungsoo; Rathwell, Kris; Kim, Won-Suk

    2014-01-17

    A mild and efficient method for the synthesis of N-arylsulfonamides in the presence of 10 mol % of CuCl is demonstrated. The reaction proceeds readily at room temperature in an open flask using a variety of sulfonyl azides and boronic acids without any base, ligand, or additive. PMID:24404934

  10. Copper-catalyzed trifluoromethylation of aryl- and vinylboronic acids with generation of CF3-radicals.

    PubMed

    Li, Yang; Wu, Lipeng; Neumann, Helfried; Beller, Matthias

    2013-04-01

    The selective trifluoromethylation of aryl- and vinylboronic acids proceeds smoothly with CF3SO2Na (Langlois reagent) in the presence of copper catalysts and t-BuOOH. Therefore, the method relies both on transition metal catalysis and selective radical reactions. Advantageously, the protocol can be performed at room temperature under an air atmosphere and avoids the issue of poor regioselectivity. PMID:23431556

  11. Acid-functionalized mesoporous carbon: an efficient support for ruthenium-catalyzed γ-valerolactone production.

    PubMed

    Villa, Alberto; Schiavoni, Marco; Chan-Thaw, Carine E; Fulvio, Pasquale F; Mayes, Richard T; Dai, Sheng; More, Karren L; Veith, Gabriel M; Prati, Laura

    2015-08-10

    The hydrogenation of levulinic acid has been studied using Ru supported on ordered mesoporous carbons (OMCs) prepared by soft-templating. P- and S-containing acid groups were introduced by postsynthetic functionalization before the addition of 1 % Ru by incipient wetness impregnation. These functionalities and the reaction conditions mediate the activity and selectivity of the levulinic acid hydrogenation. The presence of S-containing groups (Ru/OMC-S and Ru/OMC-P/S) deactivates the Ru catalysts strongly, whereas the presence of P-containing groups (Ru/OMC-P) enhances the activity compared to that of pristine Ru/OMC. Under mild conditions (70 °C and 7 bar H2 ) the catalyst shows high selectivity to γ-valerolactone (GVL; >95 %) and high stability on recycling. However, under more severe conditions (200 °C and p H 2=40 bar) Ru/OMC-P is particularly able to promote GVL ring-opening and the consecutive hydrogenation to pentanoic acid. PMID:26089180

  12. Chiral Sulfinamide/Achiral Sulfonic Acid Co-Catalyzed Enantioselective Protonation of Enol Silanes

    PubMed Central

    Beck, Elizabeth M.; Hyde, Alan M.

    2011-01-01

    The application of chiral sulfinamides and achiral sulfonic acids as a co-catalyst system for enantioselective protonation reactions is described. Structurally simple, easily accessible sulfinamides were found to induce moderate-to-high ee's in the formation of 2-aryl-substituted cycloalkanones from the corresponding trimethylsilyl enol ethers. PMID:21786775

  13. N-Butyl-2,4-dinitro-anilinium p-toluenesulfonate as a highly active and selective esterification catalyst

    PubMed Central

    Sattenapally, Narsimha; Wang, Wei; Liu, Huimin; Gao, Yong

    2013-01-01

    N-Butyl-2,4-dinitro-anilinium p-toluenesulfonate (1) was found to be a very active esterification catalyst that promotes condensation of equal mole amount of carboxylic acids and alcohols under mild conditions. This catalyst is also highly selective towards carboxylic acid and alcohol substrates at ambient temperature. PMID:24357885

  14. N-Butyl-2,4-dinitro-anilinium p-toluenesulfonate as a highly active and selective esterification catalyst.

    PubMed

    Sattenapally, Narsimha; Wang, Wei; Liu, Huimin; Gao, Yong

    2013-11-27

    N-Butyl-2,4-dinitro-anilinium p-toluenesulfonate (1) was found to be a very active esterification catalyst that promotes condensation of equal mole amount of carboxylic acids and alcohols under mild conditions. This catalyst is also highly selective towards carboxylic acid and alcohol substrates at ambient temperature.

  15. Imidase catalyzing desymmetric imide hydrolysis forming optically active 3-substituted glutaric acid monoamides for the synthesis of gamma-aminobutyric acid (GABA) analogs.

    PubMed

    Nojiri, Masutoshi; Hibi, Makoto; Shizawa, Hiroaki; Horinouchi, Nobuyuki; Yasohara, Yoshihiko; Takahashi, Satomi; Ogawa, Jun

    2015-12-01

    The recent use of optically active 3-substituted gamma-aminobutyric acid (GABA) analogs in human therapeutics has identified a need for an efficient, stereoselective method of their synthesis. Here, bacterial strains were screened for enzymes capable of stereospecific hydrolysis of 3-substituted glutarimides to generate (R)-3-substituted glutaric acid monoamides. The bacteria Alcaligenes faecalis NBRC13111 and Burkholderia phytofirmans DSM17436 were discovered to hydrolyze 3-(4-chlorophenyl) glutarimide (CGI) to (R)-3-(4-chlorophenyl) glutaric acid monoamide (CGM) with 98.1% enantiomeric excess (e.e.) and 97.5% e.e., respectively. B. phytofirmans DSM17436 could also hydrolyze 3-isobutyl glutarimide (IBI) to produce (R)-3-isobutyl glutaric acid monoamide (IBM) with 94.9% e.e. BpIH, an imidase, was purified from B. phytofirmans DSM17436 and found to generate (R)-CGM from CGI with specific activity of 0.95 U/mg. The amino acid sequence of BpIH had a 75% sequence identity to that of allantoinase from A. faecalis NBRC13111 (AfIH). The purified recombinant BpIH and AfIH catalyzed (R)-selective hydrolysis of CGI and IBI. In addition, a preliminary investigation of the enzymatic properties of BpIH and AfIH revealed that both enzymes were stable in the range of pH 6-10, with an optimal pH of 9.0, stable at temperatures below 40 °C, and were not metalloproteins. These results indicate that the use of this class of hydrolase to generate optically active 3-substituted glutaric acid monoamide could simplify the production of specific chiral GABA analogs for drug therapeutics.

  16. Kinetics of cytochrome P450 2E1-catalyzed oxidation of ethanol to acetic acid via acetaldehyde.

    PubMed

    Bell-Parikh, L C; Guengerich, F P

    1999-08-20

    The P450 2E1-catalyzed oxidation of ethanol to acetaldehyde is characterized by a kinetic deuterium isotope effect that increases K(m) with no effect on k(cat), and rate-limiting product release has been proposed to account for the lack of an isotope effect on k(cat) (Bell, L. C., and Guengerich, F. P. (1997) J. Biol. Chem. 272, 29643-29651). Acetaldehyde is also a substrate for P450 2E1 oxidation to acetic acid, and k(cat)/K(m) for this reaction is at least 1 order of magnitude greater than that for ethanol oxidation to acetaldehyde. Acetic acid accounts for 90% of the products generated from ethanol in a 10-min reaction, and the contribution of this second oxidation has been overlooked in many previous studies. The noncompetitive intermolecular kinetic hydrogen isotope effects on acetaldehyde oxidation to acetic acid ((H)(k(cat)/K(m))/(D)(k(cat)/K(m)) = 4.5, and (D)k(cat) = 1.5) are comparable with the isotope effects typically observed for ethanol oxidation to acetaldehyde, and k(cat) is similar for both reactions, suggesting a possible common catalytic mechanism. Rapid quench kinetic experiments indicate that acetic acid is formed rapidly from added acetaldehyde (approximately 450 min(-1)) with burst kinetics. Pulse-chase experiments reveal that, at a subsaturating concentration of ethanol, approximately 90% of the acetaldehyde intermediate is directly converted to acetic acid without dissociation from the enzyme active site. Competition experiments suggest that P450 2E1 binds acetic acid and acetaldehyde with relatively high K(d) values, which preclude simple tight binding as an explanation for rate-limiting product release. The existence of a rate-determining step between product formation and release is postulated. Also proposed is a conformational change in P450 2E1 occurring during the course of oxidation and the discrimination of P450 2E1 between acetaldehyde and its hydrated form, the gem-diol. This multistep P450 reaction is characterized by kinetic

  17. Monomers of cutin biopolymer: sorption and esterification on montmorillonite surfaces

    NASA Astrophysics Data System (ADS)

    Olshansky, Yaniv; Polubesova, Tamara; Chefetz, Benny

    2013-04-01

    One of the important precursors for soil organic matter is plant cuticle, a thin layer of predominantly lipids that cover all primary aerial surfaces of vascular plants. In most plant species cutin biopolymer is the major component of the cuticle (30-85% weight). Therefore cutin is the third most abundant plant biopolymer (after lignin and cellulose). Cutin is an insoluble, high molecular weight bio-polyester, which is constructed of inter-esterified cross linked hydroxy-fatty acids and hydroxyepoxy-fatty acids. The most common building blocks of the cutin are derivatives of palmitic acid, among them 9(10),16 dihydroxy palmitic acid (diHPA) is the main component. These fatty acids and their esters are commonly found in major organo-mineral soil fraction-humin. Hence, the complexes of cutin monomers with minerals may serve as model of humin. Both cutin and humin act as adsorption efficient domains for organic contaminants. However, only scarce information is available about the interactions of cutin with soil mineral surfaces, in particular with common soil mineral montmorillonite. The main hypothesize of the study is that adsorbed cutin monomers will be reconstituted on montmorillonite surface due to esterification and oligomerization, and that interactions of cutin monomers with montmorillonite will be affected by the type of exchangeable cation. Cutin monomers were obtained from the fruits of tomato (Lycopersicon esculentum). Adsorption of monomers was measured for crude Wyoming montmorillonites and montmorillonites saturated with Fe3+ and Ca2+. To understand the mechanism of monomer-clay interactions and to evaluate esterification on the clay surface, XRD and FTIR analyses of the montmorillonite-monomers complexes were performed. Our results demonstrated that the interactions of cutin monomers with montmorillonite are affected by the type of exchangeable cation. Isotherms of adsorption of cutin monomers on montmorillonites were fitted by a dual mode model of

  18. Acid-catalyzed hydrolysis of BMS-582664: degradation product identification and mechanism elucidation.

    PubMed

    Zhao, Fang; Derbin, George; Miller, Scott; Badawy, Sherif; Hussain, Munir

    2012-09-01

    BMS-582664 is an investigational drug intended for cancer treatment through oral administration. The preformulation studies revealed two unexpected degradation products under acidic conditions by reversed-phase high-performance liquid chromatography with ultraviolet detection. Additional liquid chromatography-mass spectrometry results suggested that these were cleavage (hydrolysis) products of a diaryl ether. To further understand the degradation mechanism, the reaction was carried out in (18) O-labeled water. The (18) O was found to be incorporated in only one of the two hydrolysis products. The results suggest that the corresponding α carbon in the heterocycle was unusually eletrophilic in acidic conditions probably because of the protonation of the neighboring nitrogen. This led to the selective attack by water and the consequent hydrolysis products. The study provides a new example of hydrolytic degradation of pharmaceutical compounds, and the reaction center is an aromatic heterocyclic carbon with an aryloxy substitution. PMID:22189636

  19. Homogeneous Catalyzed Reactions of Levulinic Acid: To γ-Valerolactone and Beyond.

    PubMed

    Omoruyi, Uwaila; Page, Samuel; Hallett, Jason; Miller, Philip W

    2016-08-23

    Platform chemicals derived from lignocellulosic plant biomass are viewed as a sustainable replacement for crude oil-based feedstocks. Levulinic acid (LA) is one such biomass-derived chemical that has been widely studied for further catalytic transformation to γ-valerolactone (GVL), an important 'green' fuel additive, solvent, and fine chemical intermediate. Although the transformation of LA to GVL can be achieved using heterogeneous catalysis, homogeneous catalytic systems that operate under milder reactions, give higher selectivities and can be recycled continuously are attracting considerable attention. A range of new homogeneous catalysts have now been demonstrated to efficiently convert LA to GVL and to transform LA directly to other value-added chemicals such as 1,4-pentanediol (1,4-PDO) and 2-methyltetrahydrofuran (2-MTHF). This Minireview covers recent advances in the area of homogeneous catalysis for the conversion of levulinic acid and levulinic ester derivatives to GVL and chemicals beyond GVL. PMID:27464831

  20. Chemoselective Boron-Catalyzed Nucleophilic Activation of Carboxylic Acids for Mannich-Type Reactions.

    PubMed

    Morita, Yuya; Yamamoto, Tomohiro; Nagai, Hideoki; Shimizu, Yohei; Kanai, Motomu

    2015-06-10

    The carboxyl group (COOH) is an omnipresent functional group in organic molecules, and its direct catalytic activation represents an attractive synthetic method. Herein, we describe the first example of a direct catalytic nucleophilic activation of carboxylic acids with BH3·SMe2, after which the acids are able to act as carbon nucleophiles, i.e. enolates, in Mannich-type reactions. This reaction proceeds with a mild organic base (DBU) and exhibits high levels of functional group tolerance. The boron catalyst is highly chemoselective toward the COOH group, even in the presence of other carbonyl moieties, such as amides, esters, or ketones. Furthermore, this catalytic method can be extended to highly enantioselective Mannich-type reactions by using a (R)-3,3'-I2-BINOL-substituted boron catalyst.

  1. Hydrolysis of Selected Tropical Plant Wastes Catalyzed by a Magnetic Carbonaceous Acid with Microwave.

    PubMed

    Su, Tong-Chao; Fang, Zhen; Zhang, Fan; Luo, Jia; Li, Xing-Kang

    2015-01-01

    In this study, magnetic carbonaceous acids were synthesized by pyrolysis of the homogeneous mixtures of glucose and magnetic Fe3O4 nanoparticles, and subsequent sulfonation. The synthesis conditions were optimized to obtain a catalyst with both high acid density (0.75 mmol g(-1)) and strong magnetism [magnetic saturation, Ms = 19.5 Am(2) kg(-1)]. The screened catalyst (C-SO3H/Fe3O4) was used to hydrolyze ball-milled cellulose in a microwave reactor with total reducing sugar (TRS) yield of 25.3% under the best conditions at 190 °C for 3.5 h. It was cycled for at least seven times with high catalyst recovery rate (92.8%), acid density (0.63 mmol g(-1)) and magnetism (Ms = 12.9 Am(2) kg(-1)), as well as high TRS yield (20.1%) from the hydrolysis of ball-milled cellulose. The catalyst was further successfully tested for the hydrolysis of tropical biomass with high TRS and glucose yields of 79.8% and 58.3% for bagasse, 47.2% and 35.6% for Jatropha hulls, as well as 54.4% and 35.8% for Plukenetia hulls. PMID:26648414

  2. Hydrolysis of Selected Tropical Plant Wastes Catalyzed by a Magnetic Carbonaceous Acid with Microwave

    NASA Astrophysics Data System (ADS)

    Su, Tong-Chao; Fang, Zhen; Zhang, Fan; Luo, Jia; Li, Xing-Kang

    2015-12-01

    In this study, magnetic carbonaceous acids were synthesized by pyrolysis of the homogeneous mixtures of glucose and magnetic Fe3O4 nanoparticles, and subsequent sulfonation. The synthesis conditions were optimized to obtain a catalyst with both high acid density (0.75 mmol g-1) and strong magnetism [magnetic saturation, Ms = 19.5 Am2 kg-1]. The screened catalyst (C-SO3H/Fe3O4) was used to hydrolyze ball-milled cellulose in a microwave reactor with total reducing sugar (TRS) yield of 25.3% under the best conditions at 190 °C for 3.5 h. It was cycled for at least seven times with high catalyst recovery rate (92.8%), acid density (0.63 mmol g-1) and magnetism (Ms = 12.9 Am2 kg-1), as well as high TRS yield (20.1%) from the hydrolysis of ball-milled cellulose. The catalyst was further successfully tested for the hydrolysis of tropical biomass with high TRS and glucose yields of 79.8% and 58.3% for bagasse, 47.2% and 35.6% for Jatropha hulls, as well as 54.4% and 35.8% for Plukenetia hulls.

  3. Hydrolysis of Selected Tropical Plant Wastes Catalyzed by a Magnetic Carbonaceous Acid with Microwave

    PubMed Central

    Su, Tong-Chao; Fang, Zhen; Zhang, Fan; Luo, Jia; Li, Xing-Kang

    2015-01-01

    In this study, magnetic carbonaceous acids were synthesized by pyrolysis of the homogeneous mixtures of glucose and magnetic Fe3O4 nanoparticles, and subsequent sulfonation. The synthesis conditions were optimized to obtain a catalyst with both high acid density (0.75 mmol g−1) and strong magnetism [magnetic saturation, Ms = 19.5 Am2 kg−1]. The screened catalyst (C-SO3H/Fe3O4) was used to hydrolyze ball-milled cellulose in a microwave reactor with total reducing sugar (TRS) yield of 25.3% under the best conditions at 190 °C for 3.5 h. It was cycled for at least seven times with high catalyst recovery rate (92.8%), acid density (0.63 mmol g−1) and magnetism (Ms = 12.9 Am2 kg−1), as well as high TRS yield (20.1%) from the hydrolysis of ball-milled cellulose. The catalyst was further successfully tested for the hydrolysis of tropical biomass with high TRS and glucose yields of 79.8% and 58.3% for bagasse, 47.2% and 35.6% for Jatropha hulls, as well as 54.4% and 35.8% for Plukenetia hulls. PMID:26648414

  4. Hydrolysis of tannic acid catalyzed by immobilized-stabilized derivatives of Tannase from Lactobacillus plantarum.

    PubMed

    Curiel, Jose Antonio; Betancor, Lorena; de las Rivas, Blanca; Muñoz, Rosario; Guisan, Jose M; Fernández-Lorente, Gloria

    2010-05-26

    A recombinant tannase from Lactobacillus plantarum , overexpressed in Escherichia coli , was purified in a single step by metal chelate affinity chromatography on poorly activated nickel supports. It was possible to obtain 0.9 g of a pure enzyme by using only 20 mL of chromatographic support. The pure enzyme was immobilized and stabilized by multipoint covalent immobilization on highly activated glyoxyl agarose. Derivatives obtained by multipoint and multisubunit immobilization were 500- and 1000-fold more stable than both the soluble enzyme and the one-point-immobilized enzyme in experiments of thermal and cosolvent inactivation, respectively. In addition, up to 70 mg of pure enzyme was immobilized on 1 g of wet support. The hydrolysis of tannic acid was optimized by using the new immobilized tannase derivative. The optimal reaction conditions were 30% diglyme at pH 5.0 and 4 degrees C. Under these conditions, it was possible to obtain 47.5 mM gallic acid from 5 mM tannic acid as substrate. The product was pure as proved by HPLC. On the other hand, the immobilized biocatalyst preserved >95% of its initial activity after 1 month of incubation under the optimal reaction conditions.

  5. Ruthenium-Catalyzed Oxidative Homocoupling of Arylboronic Acids in Water: Ligand Tuned Reactivity and Mechanistic Study.

    PubMed

    Tyagi, Deepika; Binnani, Chinky; Rai, Rohit K; Dwivedi, Ambikesh D; Gupta, Kavita; Li, Pei-Zhou; Zhao, Yanli; Singh, Sanjay K

    2016-06-20

    Molecular catalysts based on water-soluble arene-Ru(II) complexes ([Ru]-1-[Ru]-5) containing aniline (L1), 2-methylaniline (L2), 2,6-dimethylaniline (L3), 4-methylaniline (L4), and 4-chloroaniline (L5) were designed for the homocoupling of arylboronic acids in water. These complexes were fully characterized by (1)H, (13)C NMR, mass spectrometry, and elemental analyses. Structural geometry for two of the representative arene-Ru(II) complexes [Ru]-3 and [Ru]-4 was established by single-crystal X-ray diffraction studies. Our studies showed that the selectivity toward biaryls products is influenced by the position and the electronic behavior of various substituents of aniline ligand coordinated to ruthenium. Extensive investigations using (1)H NMR, (19)F NMR, and mass spectral studies provided insights into the mechanistic pathway of homocoupling of arylboronic acids, where the identification of important organometallic intermediates, such as σ-aryl/di(σ-aryl) coordinated arene-Ru(II) species, suggested that the reaction proceeds through the formation of crucial di(σ-aryl)-Ru intermediates by the interaction of arylboronic acid with Ru-catalyst to yield biaryl products. PMID:27276384

  6. Production and Characterization of Ethyl Ester from Crude Jatropha curcas Oil having High Free Fatty Acid Content

    NASA Astrophysics Data System (ADS)

    Kumar, Rajneesh; Dixit, Anoop; Singh, Shashi Kumar; Singh, Gursahib; Sachdeva, Monica

    2015-09-01

    The two step process was carried out to produce biodiesel from crude Jatropha curcas oil. The pretreatment process was carried out to reduce the free fatty acid content by (≤2 %) acid catalyzed esterification. The optimum reaction conditions for esterification were reported to be 5 % H2SO4, 20 % ethanol and 1 h reaction time at temperature of 65 °C. The pretreatment process reduced the free fatty acid of oil from 7 to 1.85 %. In second process, alkali catalysed transesterification of pretreated oil was carried and the effects of the varying concentrations of KOH and ethanol: oil ratios on percent ester recovery were investigated. The optimum reaction conditions for transesterification were reported to be 3 % KOH (w/v of oil) and 30 % (v/v) ethanol: oil ratio and reaction time 2 h at 65 °C. The maximum percent recovery of ethyl ester was reported to be 60.33 %.

  7. Brønsted Acid/Lewis Acid Cooperatively Catalyzed Addition of Diazoester to 2H-chromene Acetals

    PubMed Central

    Luan, Yi; Qi, Yue; Gao, Hongyi; Ma, Qianqian; Schaus, Scott E.

    2014-01-01

    A novel Brønsted acid/Lewis acid dual catalyst system has been developed to promote an efficient C–C bond formation between a range of oxocarbenium precursors derived from chromene acetals and ethyl diazoacetate. The reaction proceeds under mild conditions and is tolerant of common functionalized 2H-chromene and isochromene acetals. In addition, an asymmetric variant of diazoacetate addition towards 2H-chromene acetal is described. Continued investigations include the further optimization of asymmetric induction towards the formation of diazo ester substituted 2H-chromene. PMID:25411552

  8. Single-stage separation and esterification of cation salt carboxylates using electrodeionization

    DOEpatents

    Lin, YuPo J.; Henry, Michael; Hestekin, Jamie; Snyder, Seth W.; St. Martin, Edward J.

    2006-11-28

    A method of and apparatus for continuously making an organic ester from a lower alcohol and an organic acid is disclosed. An organic acid or salt is introduced or produced in an electrode ionization (EDI) stack with a plurality of reaction chambers each formed from a porous solid ion exchange resin wafer interleaved between anion exchange membranes or an anion exchange membrane and a cation exchange membrane or an anion exchange membrane and a bipolar exchange membranes. At least some reaction chambers are esterification chambers and/or bioreactor chambers and/or chambers containing an organic acid or salt. A lower alcohol in the esterification chamber reacts with an anion to form an organic ester and water with at least some of the water splitting with the ions leaving the chamber to drive the reaction.

  9. Topological analysis of the electronic charge density in the ethene protonation reaction catalyzed by acidic zeolite.

    PubMed

    Zalazar, M Fernanda; Peruchena, Nélida M

    2007-08-16

    In the present work, the distribution of the electronic charge density in the ethene protonation reaction by a zeolite acid site is studied within the framework of the density functional theory and the atoms in molecules (AIM) theory. The key electronic effects such as topological distribution of the charge density involved in the reaction are presented and discussed. The results are obtained at B3LYP/6-31G(**) level theory. Attention is focused on topological parameters such as electron density, its Laplacian, kinetic energy density, potential energy density, and electronic energy density at the bond critical points (BCP) in all bonds involved in the interaction zone, in the reactants, pi-complex, transition state, and alkoxy product. In addition, the topological atomic properties are determined on the selected atoms in the course of the reaction (average electron population, N(Omega), atomic net charge, q(Omega), atomic energy, E(Omega), atomic volume, v(Omega), and first moment of the atomic charge distribution, M(Omega)) and their changes are analyzed exhaustively. The topological study clearly shows that the ethene interaction with the acid site of the zeolite cluster, T5-OH, in the ethene adsorbed, is dominated by a strong O-H...pi interaction with some degree of covalence. AIM analysis based on DFT calculation for the transition state (TS) shows that the hydrogen atom from the acid site in the zeolitic fragment is connected to the carbon atom by a covalent bond with some contribution of electrostatic interaction and to the oxygen atom by closed shell interaction with some contribution of covalent character. The C-O bond formed in the alkoxy product can be defined as a weaker shared interaction. Our results show that in the transition state, the dominant interactions are partially electrostatic and partially covalent in nature, in which the covalent contribution increases as the concentration and accumulation of the charge density along the bond path between

  10. Gold/Lewis Acid Catalyzed Cycloisomerization/Diastereoselective [3 + 2] Cycloaddition Cascade: Synthesis of Diverse Nitrogen-Containing Spiro Heterocycles.

    PubMed

    Wang, Bin; Liang, Man; Tang, Jian; Deng, Yuting; Zhao, Jinhong; Sun, Hao; Tung, Chen-Ho; Jia, Jiong; Xu, Zhenghu

    2016-09-16

    A novel early and late transition-metal relay catalysis has been developed by combining a gold-catalyzed cycloisomerization and a Yb(OTf)3-catalyzed diastereoselective [3 + 2] cycloaddition with aziridines in a selective C-C bond cleavage mode. Various biologically significant complex nitrogen-containing spiro heterocycles were rapidly constructed from readily available starting materials under mild conditions. PMID:27574831

  11. Upcycling potato peel waste - Data of the pre-screening of the acid-catalyzed liquefaction.

    PubMed

    Ventura, Patrícia; Bordado, João Carlos Moura; Mateus, Maria Margarida; Galhano Dos Santos, Rui

    2016-06-01

    Herein, the data acquired regarding the preliminary and exploratory experiments conducted with potato peel as a biomass source for the direct thermochemical liquefaction is disclosed. The procedure was carried out in a 2-ethylhexanol/DEG solvent mixture at 160 °C in the presence of p-Toluenesulfonic acid. The adopted procedure afforded a bio-oil in high yield (up to 93%) after only 30 min. For longer reaction times, higher amounts of solid residues were obtained leading, consequently, to lower yields. PMID:27182538

  12. Ruthenium(II)-catalyzed oxidative C-H alkenylations of sulfonic acids, sulfonyl chlorides and sulfonamides.

    PubMed

    Ma, Wenbo; Mei, Ruhuai; Tenti, Giammarco; Ackermann, Lutz

    2014-11-10

    Twofold C-H functionalization of aromatic sulfonic acids was achieved with an in situ generated ruthenium(II) catalyst. The optimized cross-dehydrogenative alkenylation protocol proved applicable to differently substituted arenes and a variety of alkenes, including vinyl arenes, sulfones, nitriles and ketones. The robustness of the ruthenium(II) catalyst was demonstrated by the chemoselective oxidative olefination of sulfonamides as well as sulfonyl chlorides. Mechanistic studies provided support for a reversible, acetate-assisted C-H ruthenation, along with a subsequent olefin insertion.

  13. Brønsted acid catalyzed monoalkylation of anilines with trichloroacetimidates.

    PubMed

    Wallach, Daniel R; Stege, Patrick C; Shah, Jigisha P; Chisholm, John D

    2015-02-01

    Trichloroacetimidates are useful alkylating agents for aromatic amines, requiring only a catalytic amount of a Brønsted acid to facilitate the reaction. Monoalkylation predominates under these conditions. Electron-poor anilines provide superior yields, with electron-rich anilines sometimes showing competitive Friedel-Crafts alkylation. A single flask protocol with formation of the imidate in situ is demonstrated, providing a convenient method for the direct substitution of alcohols with anilines. Reaction with a chiral imidate favors a mechanism that proceeds through a carbocation intermediate. PMID:25568933

  14. Scavenging of SO 4- radical anions by mono- and dicarboxylic acids in the Mn(II)-catalyzed S(IV) oxidation in aqueous solution

    NASA Astrophysics Data System (ADS)

    Grgić, Irena; Podkrajšek, Boštjan; Barzaghi, Paolo; Herrmann, Hartmut

    The rate constants for reactions of the SO 4- radical anion with some low molecular weight monocarboxylic acids (MCAs) and dicarboxylic acids (DCAs) and their anions using the laser flash photolysis-long path laser absorption (LFP-LPLA) technique were determined. The present study contains the first measured rate constants for SO 4- reactions with glycolic, lactic, malic and malonic acid. The rate constants are found to be in the range from 10 5 to 10 7 M -1 s -1, with the lower values found for acids and higher values for their respective anions. In addition, the rate constants for scavenging of SO 4- by all investigated organics in the Mn(II)-catalyzed S(IV) autoxidation at pH 4.5 and T=25 °C were determined by means of the reversed rate method. The comparison between these rate constants and the rate constants obtained by direct measurements confirms the proposed inhibiting mechanism for the Mn(II)-catalyzed S(IV) autoxidation in the presence of monocarboxylic acids. In the case of formic acid, which causes the highest inhibition, this mechanism can explain the second part of kinetic traces (i.e. after the induction period). Surprisingly, although dicarboxylic acids are reactive toward SO 4- they do not contribute to the inhibition of S(IV) oxidation (especially malic and malonic acids).

  15. Self-catalyzed syntheses, structural characterization, DPPH radical scavenging-, cytotoxicity-, and DFT studies of phenoxyaliphatic acids of 1,8-dioxo-octahydroxanthene derivatives

    NASA Astrophysics Data System (ADS)

    Suresh Kumar, G. S.; Antony Muthu Prabhu, A.; Seethalashmi, P. G.; Bhuvanesh, N.; Kumaresan, S.

    2014-02-01

    One-pot, in-water syntheses of phenoxyaliphatic acids of 1,8-dioxo-octahydroxanthene derived from dimedone and formylphenoxyaliphatic acids are reported. Geometries of compounds 2b, 2c, and 5a have been examined crystallographically. The synthesized compounds showed better DPPH radical scavenging activity and cytotoxicity against A431 cancer cell line. The molecular properties of all synthesized xanthenes have been investigated using single crystal XRD and DFT method. Self-catalyzed Bronsted-Lowry acid catalytic behavior was also investigated by both experimental and theoretical methods.

  16. Enzymatic synthesis of γ-glutamylmethylamide from glutamic acid γ-methyl ester and methylamine catalyzed by Escherichia coli having γ-glutamyltranspeptidase activity.

    PubMed

    Xu, Lisheng; Gao, Guizhen; Wengen, Cao; Xu, Jigui; Zhao, Liang; Shi, Hongwei; Zhang, Xingtao

    2014-06-01

    A new method for the synthesis of γ-glutamylmethylamide is presented. Glutamic acid γ-methyl ester was used as substrate for γ-glutamylmethylamide synthesis catalyzed by Escherichia coli with γ-glutamyltranspeptidase activity. Reaction conditions were optimized by using 300 mM glutamic acid γ-methyl ester and 3,000 mM methylamine at pH 10 and 40 °C. Bioconversion rate of γ-glutamylmethylamide reached 87 % after 10 h. γ-Glutamyltranspeptidase was reversibly inhibited only when glutamic acid γ-methyl ester was above 300 mM.

  17. Brønsted Acid-Catalyzed Transfer Hydrogenation of Imines and Alkenes Using Cyclohexa-1,4-dienes as Dihydrogen Surrogates.

    PubMed

    Chatterjee, Indranil; Oestreich, Martin

    2016-05-20

    Cyclohexa-1,4-dienes are introduced to Brønsted acid-catalyzed transfer hydrogenation as an alternative to the widely used Hantzsch dihydropyridines. While these hydrocarbon-based dihydrogen surrogates do offer little advantage over established protocols in imine reduction as well as reductive amination, their use enables the previously unprecedented transfer hydrogenation of structurally and electronically unbiased 1,1-di- and trisubstituted alkenes. The mild procedure requires 5.0 mol % of Tf2NH, but the less acidic sulfonic acids TfOH and TsOH work equally well. PMID:27181437

  18. Kinetics and mechanism of the heterogeneous catalyzed oxidative decolorization of Acid-Blue 92 using bimetallic metal-organic frameworks

    NASA Astrophysics Data System (ADS)

    El-sharkawy, Rehab G.; El-din, Ahmed S. Badr; Etaiw, Safaa El-din H.

    2011-09-01

    The kinetics study of the oxidative decolorization of Acid-Blue 92 has been investigated by hydrogen peroxide catalyzed with bimetallic metal-organic frameworks. The used metal-organic frameworks (MOF) are [Ph 3SnCu(CN) 2·L] where L = pyrazine (pyz) 1, methylpyrazine (mepyz) 2, 4,4'-bipyridine (bpy) 3, trans-1,2-bis(4-pyridyl)ethene (tbpe) 4 or 1,2-bis(4-pyridyl)ethane (bpe) 5. The reaction was followed by conventional UV-Vis spectrophotometer at λmax = 571 nm. The reaction exhibited first-order kinetics with respect to [dye] and [H 2O 2]. The reactivity of the catalysts depends on the type of the medium and thereafter decreases in strong alkaline media. Addition of NaCl enhances the reaction rate. Also, the irradiation of the reaction with UV-light enhanced the rate of AB-92 mineralization by about 86.9%. The reaction was entropy-controlled as confirmed by the isokinetic relationship. A reaction mechanism was proposed with the formation of free radicals as an oxidant.

  19. Enantioselective acylation of β-phenylalanine acid and its derivatives catalyzed by penicillin G acylase from Alcaligenes faecalis.

    PubMed

    Li, Dengchao; Ji, Lilian; Wang, Xinfeng; Wei, Dongzhi

    2013-01-01

    This study developed a simple, efficient method for producing racemic β-phenylalanine acid (BPA) and its derivatives via the enantioselective acylation catalyzed by the penicillin G acylase from Alcaligenes faecalis (Af-PGA). When the reaction was run at 25°C and pH 10 in an aqueous medium containing phenylacetamide and BPA in a molar ratio of 2:1, 8 U/mL enzyme and 0.1 M BPA, the maximum BPA conversion efficiency at 40 min only reached 36.1%, which, however, increased to 42.9% as the pH value and the molar ratio of phenylacetamide to BPA were elevated to 11 and 3:1, respectively. Under the relatively optimum reaction conditions, the maximum conversion efficiencies of BPA derivatives all reached about 50% in a relatively short reaction time (45-90 min). The enantiomeric excess value of product (ee(p)) and enantiomeric excess value of substrate (ee(s)) were all above 98% and 95%, respectively. These results suggest that the method established in this study is practical, effective, and environmentally benign and may be applied to industrial production of enantiomerically pure BPA and its derivatives. PMID:23302108

  20. Enhancement of lipase catalyzed-fatty acid methyl esters production from waste activated bleaching earth by nullification of lipase inhibitors.

    PubMed

    Dwiarti, Lies; Ali, Ehsan; Park, Enoch Y

    2010-01-01

    This study sought to identify inhibitory factors of lipase catalyzed-fatty acid methyl esters (FAME) production from waste activated bleaching earth (wABE). During the vegetable oil refinery process, activated bleaching earth (ABE) is used for removing the impure compounds, but adsorbs vegetable oil up to 35-40% as on a weight basis, and then the wABE is discarded as waste material. The impurities were extracted from the wABE with methanol and evaluated by infra-red (IR) spectroscopy, which revealed that some were chlorophyll-plant pigments. The chlorophylls inhibited the lipase during FAME conversion from wABE. The inhibition by a mixture of chlorophyll a and b was found to be competitive. The inhibition of the enzymatic hydrolysis of waste vegetable oil contained in wABE by chlorophyll a alone was competitive, while the inhibition by chlorophyll b alone was non-competitive. Furthermore, the addition of a small amount of alkali nullified this inhibitory effect and accelerated the FAME production rate. When 0.9% KOH (w/w wABE) was added to the transesterification reaction with only 0.05% lipase (w/w wABE), the maximum FAME production rate improved 120-fold, as compared to that without the addition of KOH. The alkali-combined lipase significantly enhanced the FAME production rate from wABE, in spite of the presence of the plant pigments, and even when a lower amount of lipase was used as a catalyst.

  1. A Heteromeric Membrane-Bound Prenyltransferase Complex from Hop Catalyzes Three Sequential Aromatic Prenylations in the Bitter Acid Pathway1[OPEN

    PubMed Central

    Li, Haoxun; Ban, Zhaonan; Qin, Hao; Ma, Liya; King, Andrew J.

    2015-01-01

    Bitter acids (α and β types) account for more than 30% of the fresh weight of hop (Humulus lupulus) glandular trichomes and are well known for their contribution to the bitter taste of beer. These multiprenylated chemicals also show diverse biological activities, some of which have potential benefits to human health. The bitter acid biosynthetic pathway has been investigated extensively, and the genes for the early steps of bitter acid synthesis have been cloned and functionally characterized. However, little is known about the enzyme(s) that catalyze three sequential prenylation steps in the β-bitter acid pathway. Here, we employed a yeast (Saccharomyces cerevisiae) system for the functional identification of aromatic prenyltransferase (PT) genes. Two PT genes (HlPT1L and HlPT2) obtained from a hop trichome-specific complementary DNA library were functionally characterized using this yeast system. Coexpression of codon-optimized PT1L and PT2 in yeast, together with upstream genes, led to the production of bitter acids, but no bitter acids were detected when either of the PT genes was expressed by itself. Stepwise mutation of the aspartate-rich motifs in PT1L and PT2 further revealed the prenylation sequence of these two enzymes in β-bitter acid biosynthesis: PT1L catalyzed only the first prenylation step, and PT2 catalyzed the two subsequent prenylation steps. A metabolon formed through interactions between PT1L and PT2 was demonstrated using a yeast two-hybrid system, reciprocal coimmunoprecipitation, and in vitro biochemical assays. These results provide direct evidence of the involvement of a functional metabolon of membrane-bound prenyltransferases in bitter acid biosynthesis in hop. PMID:25564559

  2. Biomimetic Fenton-catalyzed lignin depolymerization to high-value aromatics and dicarboxylic acids.

    PubMed

    Zeng, Jijiao; Yoo, Chang Geun; Wang, Fei; Pan, Xuejun; Vermerris, Wilfred; Tong, Zhaohui

    2015-03-01

    By mimicking natural lignin degradation systems, the Fenton catalyst (Fe(3+), H2O2) can effectively facilitate lignin depolymerization in supercritical ethanol (7 MPa, 250 °C) to give organic oils that consist of mono- and oligomeric aromatics, phenols, dicarboxylic acids, and their derivatives in yields up to (66.0±8.5) %. The thermal properties, functional groups, and surface chemistry of lignin before and after Fenton treatment were examined by thermogravimetric analysis, pyrolysis-gas chromatography-mass spectrometry, (31)P NMR spectroscopy, and X-ray photoelectron spectroscopy. The results suggest that the Fenton catalyst facilitates lignin depolymerization through cleavage of β-ether bonds between lignin residues. The formation of a lignin-iron chelating complex effectively depresses lignin recondensation; thus minimizing charcoal formation and enhancing the yield of liquid products.

  3. Lewis Acidity of Bis(perfluorocatecholato)silane: Aldehyde Hydrosilylation Catalyzed by a Neutral Silicon Compound

    DOE PAGES

    Liberman-Martin, Allegra L.; Bergman, Robert G.; Tilley, T. Don

    2015-04-16

    Bis(perfluorocatecholato)silane Si(cat(F)2 was prepared, and stoichiometric binding to Lewis bases was demonstrated with fluoride, triethylphosphine oxide, and N,N'-diisopropylbenzamide. The potent Lewis acidity of Si(cat(F)2 was suggested from catalytic hydrosilylation and silylcyanation reactions with aldehydes. Mechanistic studies of hydrosilylation using an optically active silane substrate, R-(+)-methyl-(1-naphthyl)phenylsilane, proceeded with predominant stereochemical retention at silicon, consistent with a carbonyl activation pathway. The enantiospecificity was dependent on solvent and salt effects, with increasing solvent polarity or addition of NBu4BAr(F)4 leading to a diminished enantiomeric ratio. The medium effects are consistent with an ionic mechanism, wherein hydride transfer occurs prior to silicon-oxygen bond formation.

  4. Lewis Acidity of Bis(perfluorocatecholato)silane: Aldehyde Hydrosilylation Catalyzed by a Neutral Silicon Compound

    SciTech Connect

    Liberman-Martin, Allegra L.; Bergman, Robert G.; Tilley, T. Don

    2015-04-16

    Bis(perfluorocatecholato)silane Si(cat(F)2 was prepared, and stoichiometric binding to Lewis bases was demonstrated with fluoride, triethylphosphine oxide, and N,N'-diisopropylbenzamide. The potent Lewis acidity of Si(cat(F)2 was suggested from catalytic hydrosilylation and silylcyanation reactions with aldehydes. Mechanistic studies of hydrosilylation using an optically active silane substrate, R-(+)-methyl-(1-naphthyl)phenylsilane, proceeded with predominant stereochemical retention at silicon, consistent with a carbonyl activation pathway. The enantiospecificity was dependent on solvent and salt effects, with increasing solvent polarity or addition of NBu4BAr(F)4 leading to a diminished enantiomeric ratio. The medium effects are consistent with an ionic mechanism, wherein hydride transfer occurs prior to silicon-oxygen bond formation.

  5. Metal-Free Ammonia-Borane Dehydrogenation Catalyzed by a Bis(borane) Lewis Acid.

    PubMed

    Lu, Zhenpin; Schweighauser, Luca; Hausmann, Heike; Wegner, Hermann A

    2015-12-14

    The storage of energy in a safe and environmentally benign way is one of the main challenges of today's society. Ammonia-borane (AB=NH3 BH3 ) has been proposed as a possible candidate for the chemical storage of hydrogen. However, the efficient release of hydrogen is still an active field of research. Herein, we present a metal-free bis(borane) Lewis acid catalyst that promotes the evolution of up to 2.5 equivalents of H2 per AB molecule. The catalyst can be reused multiple times without loss of activity. The moderate temperature of 60 °C allows for controlling the supply of H2 on demand simply by heating and cooling. Mechanistic studies give preliminary insights into the kinetics and mechanism of the catalytic reaction. PMID:26537288

  6. Selective rhodium-catalyzed reduction of tertiary amides in amino acid esters and peptides.

    PubMed

    Das, Shoubhik; Li, Yuehui; Bornschein, Christoph; Pisiewicz, Sabine; Kiersch, Konstanze; Michalik, Dirk; Gallou, Fabrice; Junge, Kathrin; Beller, Matthias

    2015-10-12

    Efficient reduction of the tertiary amide bond in amino acid derivatives and peptides is described. Functional group selectivity has been achieved by applying a commercially available rhodium precursor and bis(diphenylphosphino)propane (dppp) ligand together with phenyl silane as a reductant. This methodology allows for specific reductive derivatization of biologically interesting peptides and offers straightforward access to a variety of novel peptide derivatives for chemical biology studies and potential pharmaceutical applications. The catalytic system tolerates a variety of functional groups including secondary amides, ester, nitrile, thiomethyl, and hydroxy groups. This convenient hydrosilylation reaction proceeds at ambient conditions and is operationally safe because no air-sensitive reagents or highly reactive metal hydrides are needed. PMID:26189442

  7. Selective rhodium-catalyzed reduction of tertiary amides in amino acid esters and peptides.

    PubMed

    Das, Shoubhik; Li, Yuehui; Bornschein, Christoph; Pisiewicz, Sabine; Kiersch, Konstanze; Michalik, Dirk; Gallou, Fabrice; Junge, Kathrin; Beller, Matthias

    2015-10-12

    Efficient reduction of the tertiary amide bond in amino acid derivatives and peptides is described. Functional group selectivity has been achieved by applying a commercially available rhodium precursor and bis(diphenylphosphino)propane (dppp) ligand together with phenyl silane as a reductant. This methodology allows for specific reductive derivatization of biologically interesting peptides and offers straightforward access to a variety of novel peptide derivatives for chemical biology studies and potential pharmaceutical applications. The catalytic system tolerates a variety of functional groups including secondary amides, ester, nitrile, thiomethyl, and hydroxy groups. This convenient hydrosilylation reaction proceeds at ambient conditions and is operationally safe because no air-sensitive reagents or highly reactive metal hydrides are needed.

  8. Lewis Acidity of Bis(perfluorocatecholato)silane: Aldehyde Hydrosilylation Catalyzed by a Neutral Silicon Compound.

    PubMed

    Liberman-Martin, Allegra L; Bergman, Robert G; Tilley, T Don

    2015-04-29

    Bis(perfluorocatecholato)silane Si(cat(F))2 was prepared, and stoichiometric binding to Lewis bases was demonstrated with fluoride, triethylphosphine oxide, and N,N'-diisopropylbenzamide. The potent Lewis acidity of Si(cat(F))2 was suggested from catalytic hydrosilylation and silylcyanation reactions with aldehydes. Mechanistic studies of hydrosilylation using an optically active silane substrate, R-(+)-methyl-(1-naphthyl)phenylsilane, proceeded with predominant stereochemical retention at silicon, consistent with a carbonyl activation pathway. The enantiospecificity was dependent on solvent and salt effects, with increasing solvent polarity or addition of NBu4BAr(F)4 leading to a diminished enantiomeric ratio. The medium effects are consistent with an ionic mechanism, wherein hydride transfer occurs prior to silicon-oxygen bond formation.

  9. Sulfamic Acid-Catalyzed Lead Perovskite Formation for Solar Cell Fabrication on Glass or Plastic Substrates.

    PubMed

    Guo, Yunlong; Sato, Wataru; Shoyama, Kazutaka; Nakamura, Eiichi

    2016-04-27

    Lead perovskite materials such as methylammonium triiodoplumbate(II) (CH3NH3PbI3, PV) are promising materials for printable solar cell (SC) applications. The preparation of PV involves a series of energetically costly cleavages of the μ-iodo bridges via conversion of a mixture of PbI2 (PI) and methylammonium iodide (CH3NH3I, MAI) in N,N-dimethylformamide (DMF) into a precursor solution containing a polymeric strip of a plumbate(II) dimer [(MA(+))2(PbI3(-))2·(DMF)2]m, which then produces a perovskite film with loss of DMF upon spin-coating and heating of the substrate. We report here that the PI-to-PV conversion and the PV crystal growth to micrometer size can be accelerated by a small amount of zwitterionic sulfamic acid (NH3SO3, SA) and that sulfamic acid facilitates electron transfer to a neighboring electron-accepting layer in an SC device. As a result, an SC device on indium tin oxide (ITO)/glass made of a 320 nm thick PV film using 0.7 wt % SA showed a higher short-circuit current, open-circuit voltage, and fill factor and hence a 22.5% higher power conversion efficiency of 16.02% compared with the device made without SA. The power conversion efficiency value was reproducible (±0.3% for 25 devices), and the device showed very small hysteresis. The device without any encapsulation showed a respectable longevity on a shelf under nitrogen under ambient light. A flexible device similarly fabricated on ITO/poly(ethylene naphthalate) showed an efficiency of 12.4%. PMID:27054265

  10. An N-Heterocyclic Carbene-Catalyzed Oxidative γ-Aminoalkylation of Saturated Carboxylic Acids through in Situ Activation Strategy: Access to δ-Lactam.

    PubMed

    Que, Yonglei; Xie, Yuanwei; Li, Tuanjie; Yu, Chenxia; Tu, Shujiang; Yao, Changsheng

    2015-12-18

    An N-Heterocyclic Carbene (NHC)-catalyzed oxidative formal [4 + 2] annulation of acylhydrazones with saturated carboxylic acids bearing γ-H to assemble δ-lactams featuring a chiral carbon stereogenic center was developed through an in situ activation strategy. The ready availability of the starting materials, excellent enantioselectivity, facile assembly, high yields, and potential biological significance of the final products make this protocol an attractive alternative for the construction of the pyridinone scaffold. PMID:26646554

  11. Acid-Catalyzed Multicomponent Tandem Double Cyclization: A One-pot, Metal-free Route to Synthesize Polyfunctional 4,9-Dihydropyrrolo[2,1-b]quinazolines.

    PubMed

    Cai, Qun; Li, Deng-Kui; Zhou, Rong-Rong; Zhuang, Shi-Yi; Ma, Jin-Tian; Wu, Yan-Dong; Wu, An-Xin

    2016-09-01

    An acid-catalyzed multicomponent tandem double cyclization protocol has been developed for the synthesis of polyfunctional 4,9-dihydropyrrolo[2,1-b]quinazolines from simple and readily available arylglyoxal monohydrates, 2-aminobenzylamine, and trans-β-nitrostyrenes. This practical and metal-free reaction proceeds through an imine formation/cyclization/Michael addition/Henry cyclization protocol, resulting in the construction of four new bonds and two ring moieties directly in one pot.

  12. Lewis acid catalyzed [2+2] cycloaddition of ynamides and propargyl silyl ethers: synthesis of alkylidenecyclobutenones and their reactivity in ring-opening and ring expansion.

    PubMed

    Chen, Ling; Cao, Jian; Xu, Zheng; Zheng, Zhan-Jiang; Cui, Yu-Ming; Xu, Li-Wen

    2016-07-21

    A family of four-membered enones, polysubstituted alkylidenecyclobutenones, were easily prepared by a Lewis acid catalyzed [2+2] cycloaddition of ynamides and propargyl silyl ethers. This challenging regioselective [2+2] cycloaddition enables the efficient construction and conversion of four-membered enones, which provides high-value and structurally diverse products through the unexpected ring-opening and ring expansion of alkylidenecyclobutenone with Grignard reagents, organolithium, primary amines, and water. PMID:27387596

  13. Suzuki–Miyaura cross-coupling reaction of 1-aryltriazenes with arylboronic acids catalyzed by a recyclable polymer-supported N-heterocyclic carbene–palladium complex catalyst

    PubMed Central

    Nan, Guangming; Ren, Fang

    2010-01-01

    Summary The Suzuki–Miyaura cross-coupling reaction of 1-aryltriazenes with arylboronic acids catalyzed by a recyclable polymer-supported Pd–NHC complex catalyst has been realized for the first time. The polymer-supported catalyst can be re-used several times still retaining high activity for this transformation. Various aryltriazenes were investigated as electrophilic substrates at room temperature to give biaryls in good to excellent yields and showed good chemoselectivity over aryl halides in the reactions. PMID:20703375

  14. Efficient synthesis of pyrrolo[1,2-a]quinoxalines catalyzed by a Brønsted acid through cleavage of C-C bonds.

    PubMed

    Xie, Caixia; Feng, Lei; Li, Wanli; Ma, Xiaojun; Ma, Xinkun; Liu, Yihan; Ma, Chen

    2016-09-28

    An efficient and convenient one-pot domino reaction for the direct synthesis of pyrrolo[1,2-a]quinoxalines has been developed. This approach utilizes an imine formation reaction, SEAr reaction and cleavage of C-C bonds catalyzed by a Brønsted acid. β-Diketones and β-keto esters are both well tolerated to give the corresponding products in moderate to excellent yields. PMID:27541576

  15. Palladium-Catalyzed Synthesis of (Hetero)Aryl Alkyl Sulfones from (Hetero)Aryl Boronic Acids, Unactivated Alkyl Halides, and Potassium Metabisulfite.

    PubMed

    Shavnya, Andre; Hesp, Kevin D; Mascitti, Vincent; Smith, Aaron C

    2015-11-01

    A palladium-catalyzed one-step synthesis of (hetero)aryl alkyl sulfones from (hetero)arylboronic acids, potassium metabisulfite, and unactivated or activated alkylhalides is described. This transformation is of broad scope, occurs under mild conditions, and employs readily available reactants. A stoichiometric experiment has led to the isolation of a catalytically active dimeric palladium sulfinate complex, which was characterized by X-ray diffraction analysis.

  16. Z-Selective Synthesis of γ,δ-Unsaturated Ketones via Pd-Catalyzed Ring Opening of 2-Alkylenecyclobutanones with Arylboronic Acids.

    PubMed

    Zhou, Yao; Rao, Changqing; Song, Qiuling

    2016-08-19

    Pd-catalyzed 1,2-addition (instead of 1,4-addition) of arylboronic acids to 2-alkylenecyclobutanones followed by β-carbon elimination from the resulting palladium cyclobutanolates to afford γ,δ-unsaturated ketones was developed. The desired γ,δ-unsaturated ketones were obtained in good to excellent yields with Z/E selectivities of up to >99:1 and a broad spectrum of functional group tolerability. PMID:27479861

  17. Scope and limitations of aliphatic Friedel-Crafts alkylations. Lewis acid catalyzed addition reactions of alkyl chlorides to carbon-carbon double bonds

    SciTech Connect

    Mayr, H.; Striepe, W.

    1983-04-22

    Lewis acid catalyzed addition reactions of alkyl halides with unsaturated hydrocarbons have been studied. 1:1 addition products are formed if the addends dissociate faster than the corresponding products; otherwise, polymerization takes place. For reaction conditions under which these compounds exist mainly undissociated, solvolysis constants of model compounds can be used to predict the outcome of any such addition reactions if systems with considerable steric hindrance are excluded.

  18. Chiral phosphoric acid catalyzed highly enantioselective Friedel-Crafts alkylation reaction of C3-substituted indoles to β,γ-unsaturated α-ketimino esters.

    PubMed

    Bi, Bo; Lou, Qin-Xin; Ding, Yu-Yang; Chen, Sheng-Wei; Zhang, Sha-Sha; Hu, Wen-Hui; Zhao, Jun-Ling

    2015-02-01

    A highly enantioselective C2 Friedel-Crafts alkylation reaction of 3-substituted indoles to β,γ-unsaturated α-ketimino esters has been developed. This reaction was efficiently catalyzed by a chiral phosphoric acid catalyst. The corresponding C2-substituted indole derivatives, bearing an α-ketimino ester motif, were obtained in moderate to high yields (up to 93%) and with high enantioselectivities (up to >99% ee). PMID:25594307

  19. Nickel-Catalyzed Cross Couplings of Benzylic Ammonium Salts and Boronic Acids: Stereospecific Formation of Diarylethanes via C–N Bond Activation

    PubMed Central

    Maity, Prantik; Shacklady-McAtee, Danielle M.; Yap, Glenn P. A.; Sirianni, Eric R.; Watson, Mary P.

    2014-01-01

    We have developed a nickel-catalyzed cross coupling of benzylic ammonium triflates with aryl boronic acids to afford diarylmethanes and diarylethanes. This reaction proceeds under mild reaction conditions and with exceptional functional group tolerance. Further, it transforms branched benzylic ammonium salts to diarylethanes with excellent chirality transfer, offering a new strategy for the synthesis of highly enantioenriched diarylethanes from readily available chiral benzylic amines. PMID:23268734

  20. Acid-Catalyzed Algal Biomass Pretreatment for Integrated Lipid and Carbohydrate-Based Biofuels Production

    SciTech Connect

    Laurens, L. M. L.; Nagle, N.; Davis, R.; Sweeney, N.; Van Wychen, S.; Lowell, A.; Pienkos, P. T.

    2014-11-12

    One of the major challenges associated with algal biofuels production in a biorefinery-type setting is improving biomass utilization in its entirety, increasing the process energetic yields and providing economically viable and scalable co-product concepts. We demonstrate the effectiveness of a novel, integrated technology based on moderate temperatures and low pH to convert the carbohydrates in wet algal biomass to soluble sugars for fermentation, while making lipids more accessible for downstream extraction and leaving a protein-enriched fraction behind. We studied the effect of harvest timing on the conversion yields, using two algal strains; Chlorella and Scenedesmus, generating biomass with distinctive compositional ratios of protein, carbohydrate, and lipids. We found that the late harvest Scenedesmus biomass had the maximum theoretical biofuel potential at 143 gasoline gallon equivalent (GGE) combined fuel yield per dry ton biomass, followed by late harvest Chlorella at 128 GGE per ton. Our experimental data show a clear difference between the two strains, as Scenedesmus was more successfully converted in this process with a demonstrated 97 GGE per ton. Our measurements indicated a release of >90% of the available glucose in the hydrolysate liquors and an extraction and recovery of up to 97% of the fatty acids from wet biomass. Techno-economic analysis for the combined product yields indicates that this process exhibits the potential to improve per-gallon fuel costs by up to 33% compared to a lipids-only process for one strain, Scenedesmus, grown to the mid-point harvest condition.