- How is chemical interesterification initiated: Nucleophilic substitution or α-proton abstraction?
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Esters of carboxylic acids including 2-methylhexanoic, 2-methylbutyric, 2,2-dimethyl-4-pentenoic, palmitic, and oleic acids were tested as substrates in methoxide-catalyzed interesterification and transesterification. The aliphatic acid esters participated in the ester-ester interchange upon addition of catalytic sodium methoxide. Their isopropyl esters also produced methyl esters on heating with sodium methoxide. The esters of dimethyl-substituted acids did not participate in the ester-ester interchange. Their isopropyl esters did not react with methoxide to produce methyl esters. However, upon addition of methanol with sodium methoxide, their methyl esters were produced. These results indicate that the first step in interesterification is possibly that methoxide abstracts the α-hydrogen of an ester to form a carbanion. Interesterification is then likely completed via a Claisen condensation mechanism involving the β-keto ester anion as the active intermediate. The β-keto ester anion contains positively charged ketone and acyl carbons that are active sites for nucleophilic attack by anions such as methoxide and glycerinate, which would produce a methyl ester or rearrange acyls randomly. On the other hand, transesterification is a nucleophilic substitution by methoxide at the acyl carbon in the presence of methanol.
- Liu, Linsen
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- Synthesis and evaluation of a series of α-hydroxy ethers derived from isopropyl oleate
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Several fatty derivatives with bulky moieties were prepared by treatment of epoxidized isopropyl oleate with a number of alcohols in the presence of sulfuric acid catalyst to provide a series of α-hydroxy ethers in good yield. The materials were analyzed for cold flow performance through cloud point and pour point determinations. The most promising α-hydroxy ether produced in this study, with respect to both low temperature behavior and economic criteria, was isopropyl 9(10)-(2-ethylhexoxy)-10(9)-hydroxystearate, which has a cloud point of -23°C and pour point of-24°C. Copyright
- Moser, Bryan R.,Erhan, Sevim Z.
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- Catalytic transfer hydrogenation of oleic acid to octadecanol over magnetic recoverable cobalt catalysts
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Efficient transformation of biomass into fuel and chemicals under mild conditions with cost-effective and environmentally friendly characters is highly desirable but still challenging. Herein, a scalable and Earth-abundant cobalt catalyst was used for selective catalytic transfer hydrogenation (CTH) of unsaturated fatty acids to fatty alcohols with sustainable isopropanol as a hydrogen donor. By tuning the surface Co composition by varying the reduction temperature, the catalytic performance could be easily boosted. At 200 °C in 4 h, the optimal catalyst Co-350 (reduced at 350 °C) gives 100% oleic acid conversion with 91.9% octadecanol selectivity. Various characterization studies reveal that the co-existence of Coδ+ and Co0 over the cobalt core might be responsible for its high performance for CTH of oleic acid. This catalyst could be magnetically separated and is highly stable for reusing ten times. Moreover, this cobalt catalyst is relatively cheap and easy to scale-up, thus achieving a low-cost transformation of biomass into high value-added chemicals.
- Wang, Juncheng,Nie, Renfeng,Xu, Ling,Lyu, Xilei,Lu, Xiuyang
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supporting information
p. 314 - 320
(2019/01/28)
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- Revealing the Roles of Subdomains in the Catalytic Behavior of Lipases/Acyltransferases Homologous to CpLIP2 through Rational Design of Chimeric Enzymes
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The lipases/acyltransferases homologous to CpLIP2 of Candida parapsilosis efficiently catalyze acyltransfer reactions in lipid/water media with high water activity (aW>0.9). Two new enzymes of this family, CduLAc from Candida dubliniensis and CalLAc8 from Candida albicans, were characterized. Despite 82 % sequence identity, the two enzymes have significant differences in their catalytic behaviors. In order to understand the roles played by the different subdomains of these proteins (main core, cap and C-terminal flap), chimeric enzymes were designed by rational exchange of cap and C-terminal flap, between CduLAc and CalLAc8. The results show that the cap region plays a significant role in substrate specificity; the main core was found to be the most important part of the protein for acyltransfer ability. Similar exchanges were made with CAL-A from Candida antarctica, but only the C-terminal exchange was successful. Yet, the role of this domain was not clearly elucidated, other than that it is essential for activity.
- Jan, Anne-Hélène,Dubreucq, éric,Subileau, Maeva
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p. 941 - 950
(2017/05/26)
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- Epoxidized fatty acid ester plasticizer epoxidized fatty acid ester plasticizer and manufacturing method
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Epoxidized fatty acid alkyl ester and methods for making epoxidized fatty acid alkyl ester. The epoxidized fatty acid alkyl ester is prepared from a fatty acid alkyl ester starting material comprising at least one of mono-unsaturated and di-unsaturated fatty acid alkyl ester molecules in a combined amount of at least 85 weight percent. Such epoxidized fatty acid alkyl esters can be employed in plasticizer compositions, either alone or in combination with other plasticizers, such as epoxidized natural oils. Such plasticizers in turn may be used in the formation of polymeric compositions.
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Paragraph 0066
(2017/01/26)
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- SO3H and NH2+ functional carbon-based solid acid catalyzed transesterification and biodiesel production
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A SO3H and NH2+ functional carbon-based solid acid was used as a highly active heterogeneous catalyst for the transesterification of various carboxylic methyl esters with alcohols under mild conditions. It also showed high catalytic performance for transesterification of triolein with methanol or isopropanol. Furthermore, it was able to catalyze simultaneous esterification and transesterification of rice oil and butter respectively, the yields of biodiesel obtained were up to 94%, and the catalyst could be easily recovered and reused more than ten times without loss of activity, which indicated the carbon-based solid acid was a potential catalyst for the biodiesel industry.
- Cai, Liangzhen,Meng, Decai,Zhan, Shaoqi,Yang, Xiaoxia,Liu, Taoping,Pu, Huiming,Tao, Xiaochun
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p. 72146 - 72149
(2015/09/08)
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- The 3D model of the lipase/acyltransferase from Candida parapsilosis, a tool for the elucidation of structural determinants in CAL-A lipase superfamily
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Abstract Because lipids are hydrophobic, the development of efficient bioconversions in aqueous media free of organic solvents is particularly challenging for green oleochemistry. Within this aim, enzymes exhibiting various abilities to catalyze acyltransfer reaction in water/lipid systems have been identified. Among these, CpLIP2 from Candida parapsilosis has been characterized as a lipase/acyltransferase, able to catalyze acyltransfer reactions preferentially to hydrolysis in the presence of particularly low acyl acceptor concentration and high thermodynamic activity of water (aw > 0.9). Lipase/acyltransferases are thus of great interest, being able to produce new esters at concentrations above the thermodynamic equilibrium of hydrolysis/esterification with limited to no release of free fatty acids. Here, we present a 3D model of CpLIP2 based on homologies with crystallographic structures of Pseudozyma antarctica lipase A. Indeed, the two enzymes have 31% of identity in their primary sequence, yielding a same general structure, but different catalytic properties. The quality of the calculated CpLIP2 model was confirmed by several methods. Limited proteolysis confirmed the location of some loops at the surface of the protein 3D model. Directed mutagenesis also supported the structural model constructed on CAL-A template: the functional properties of various mutants were consistent with their structure-based putative involvement in the oxyanion hole, substrate specificity, acyltransfer or hydrolysis catalysis and structural stability. The CpLIP2 3D model, in comparison with CAL-A 3D structure, brings insights for the elucidation and improvement of the structural determinants involved in the exceptional acyltransferase properties of this promising biocatalyst and of homologous enzymes of the same family.
- Subileau, Maeva,Jan, Anne-Hélène,Nozac'h, Hervé,Pérez-Gordo, Marina,Perrier, Véronique,Dubreucq, Eric
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p. 1400 - 1411
(2015/08/03)
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- Studies on the lipase-catalyzed esterification of alkyl oleates in solvent-free systems
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The alkyl oleates were prepared by esterification of oleic acid with alkyl alcohols catalyzed by the lipase from Candida sp. 99-125 in solvent-free system. The influence of several factors, including enzyme concentration, temperature, molar ratio between oleic acid and alkyl alcohols, the structure of alcohols and water content, was also investigated. The results indicated that the reactions catalyzed by Candida sp. lipase at 20 °C, in the presence of 5% (w/w) lipase, on the molar ratio of 1:1 between oleic acid and alcohols, afforded products in high yield and showed high selectivity to primary alcohols. The enzymatic synthesis gave purer products, compared with the conventional chemical synthesis. The lipase from Candida sp. 99-125 was identified to be an effective catalyst in the esterification of alcohol and oleic acid at low temperature.
- Zhong, Hui,Fang, Zheng,Zou, Baohua,Li, Xin,Ouyang, Pingkai,Guo, Kai
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p. 114 - 117
(2013/05/08)
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- Novel and highly efficient SnBr2-catalyzed esterification reactions of fatty acids: The notable anion ligand effect
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In this work, the efficiency of Lewis acid catalysts, SnX2 (X = F-, Cl-, Br-, or -OAc), was investigated on the esterification reactions of fatty acids (i.e., myristic, palmitic, stearic, oleic, linoleic, and linoleic) with different alcohols (i.e., methyl, ethyl, propyl, isopropyl, and butyl alcohol). Tin(II) bromide was the most active catalyst in all reactions studied. We investigated the effects of main reaction parameters, such as catalyst concentration, temperature, and nature of alcohol and fatty acid. The highest activity of SnBr2 catalyst was discussed in terms of its lower activation energy, higher Lewis acid strength, and higher softness of anionic ligand. Finally, the SnBr 2 catalyst can be easily recovered and reused without loss of catalytic activity. Graphical Abstract: Effect of the tin catalyst nature on the oleic acid esterification with ethyl alcohol. [Figure not available: see fulltext.]
- Ferreira, Arthur Batista,Cardoso, Abiney Lemos,Da Silva, Marcio Jose
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p. 1240 - 1246
(2014/01/06)
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- Mechanistic study of the synthesis of CdSe nanocrystals: Release of selenium
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We outline a reaction pathway for the cleavage of the P=Se bond in trialkylphosphine selenide during the synthesis of CdSe nanocrystals. The reaction between cadmium carboxylate and trimethylphosphine selenide in the presence of an alcohol produces alkoxytrimethylphosphonium (2). Control experiments and density functional theory calculations suggested that the cleavage of the P=Se bond is initiated by nucleophilic attack of carboxylate on a Cd2+-activated phosphine selenide to produce an acyloxytrialkylphosphonium intermediate (1), which is converted to 2 in the presence of an alcohol.
- Garcia-Rodriguez, Raul,Liu, Haitao
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p. 1400 - 1403
(2012/03/12)
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- Melting points and viscosities of fatty acid esters that are potential targets for engineered oilseed
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Our previous isolation of branched-chain fatty acid (BCFA) methyl esters from lanolin was improved and scaled up. Also, oleate esters of isopropanol, oleyl alcohol and normal alcohols of 1-12 carbons chain lengths were prepared. Esters were made by interesterification with sodium alcoholates and by esterification with Candida antarctica lipase. It proved easier to obtain pure esters by the enzymatic synthesis. Melting points and viscosities over the range of 0-70 °C were determined in order to better identify potential lubricant targets that might be produced by genetically modified oilseed crops. Isopropyl and butyl oleate have melting points of -33 and -32 °C, respectively and viscosities that range from ~17 cp (0 °C) to ~2.5 cp (70 °C). They should have suitable stability for lubricants. BCFA esters had viscosities similar to their straight chain analogs. Viscosities increased with alcohol chain length and decreased with temperature. The dependence of viscosity on temperature was fit with an equation based on Erying's rate equation. Some esters with branched acid or branched alcohol moieties, and some oleate esters might be utilized as biolubricants or biofuels on the basis of their melting points and viscosities.
- Yao, Linxing,Hammond, Earl,Wang, Tong
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- Diesters from oleic acid: Synthesis, low temperature properties, and oxidation stability
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Several diesters were prepared from commercially available oleic acid and common organic acids. The key step in the three step synthesis of oleochemical diesters entails a ring opening esterification of alkyl 9,10-epoxyoctadecanoates (alkyl: propyl, isopropyl, octyl, 2-ethylhexyl) using propionic and octanoic acids without the need for either solvent or catalyst. Each synthetic diester was evaluated for both low temperature operability and oxidation stability through measurement of cloud point, pour point, oxidation onset temperature, and signal maximum temperature. It was discovered that increasing chain length of the mid-chain ester and branching in the end-chain ester had a positive influence on the low temperature properties of diesters. Improved oxidation stability is achieved when the chain length of the mid-chain ester is decreased. Additionally, the mid-chain ester plays a larger role in oxidation stability than the end-chain ester. These products may prove useful in the search for bio-based industrial materials, such as lubricants, surfactants, and fuel additives.
- Moser, Bryan R.,Sharma, Brajendra K.,Doll, Kenneth M.,Erhan, Sevim Z.
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p. 675 - 680
(2008/09/21)
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- Improvement in the gas chromatographic resolution of petroselinate from oleate
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In the extraction of oils from seeds of the genus Coriandrum, GC separations of petroselinate from oleate often gave poor resolution of these two isomers. Oleic and petroselinic acids were esterified with a series of alcohols (methanol, ethanol, 1 propanol, 2-propanol, 2-methyl-1 -propanol, 1 -butanol, 3-methyl1-butanol, and 2-ethyl-1-hexanol). GC resolution of the A6 from the Δ9 and Δ11 octadecenoates was examined for all ester derivatives on a polar phase column. The Δ6 and Δ9 isomers were unresolved as methyl esters; however, the 2-ethyl-1-hexyl esters gave baseline separation of all three isomers under temperature programming conditions. When isothermal conditions were optimized for each ester, separation of these isomers was possible with good resolution values (>89%) for all the alcohols except methanol, which had a partial resolution of 51%. The rates of esterification of all the alcohols were determined for reactions with both oleic acid and triolein using potassium hydroxide as the esterification catalyst. Methanol gave the largest rate constant in both acid and oil esterification reactions with a rate constant 10-fold better than all of the other alcohols. Based on rates of reaction, resolution of petroselinate from oleate, and removal of residual alcohol, the ethyl ester derivative appears to be the best choice for seed oils containing petroselinic acid. Copyright
- Isbell, Terry A.,Green, Lindsay A.,DeKeyser, Stephanie S.,Manthey, Linda K.,Kenar, James A.,Cermak, Steven C.
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p. 429 - 434
(2007/10/03)
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- Synthesis and analysis of the C1-C18 alkyl oleates
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The C1-C18 alkyl oleates were prepared in n-hexane by esterification of oleic acid with either the primary and secondary C1-C6 alcohols or the primary fatty C8-C18 alcohols. The esterification was acid-catalyzed in the presence of p-toluene sulfonic acid (p-TSA) in a pseudo-homogeneous phase, or in the presence of the sulfonic macroporous resin (K2411) in the heterogeneous phase. The purified alkyl oleates were characterized by 13C-NMR. The oleic acid/alkyl oleate mixtures were analyzed by high-performance liquid chromatography (HPLC).
- Vieville, Corinne,Mouloungui, Zephirin,Gaset, Antoine
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p. 101 - 108
(2007/10/02)
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- Process for the production of fatty alcohols
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An improved process for the production of fatty alcohols is provided. The fatty alcohols are produced by hydrogenation of lower alkyl esters, especially methyl esters, of fatty acids derived from natural triglycerides, under conditions which minimize formation of by-product alkanes and ethers. The hydrogenation is followed by refining of any resulting ester-containing hydrogenation product to produce a substantially ester free fatty alcohol.
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