Esterification of acids

Esterification of acid chlorides (Schotten-Baumann reaction) ... 

Note. This excellent method, which proceeds with the intermediacy of the trimethylsilyl carboxylates, is equally applicable to esterifications of acids with simple alcohols, which are then used as solvent. 

Alkoxydehydroxylation - Enzymatic Esterification of Acids with Alcohols... 

The traditional catalyst used for esterification of acids to methyl esters is sulfuric acid. Homogeneous sulfuric acid catalysis has many downsides. When using sulfuric acid, much capital expense is required for Hastalloy and/or other specialty metals of construction. Homogeneous catalysis results in the contamination of the product by sulfur containing species. Therefore, neutralization and removal of acid is required to meet biodiesel specifications and to protect the downstream transesterification reactor. Inevitably, when using sulfuric acid, organic sulfur compounds will be produced. These products will cause the resultant biodiesel to fail specification tests. 

Kelkar MA, Gogate PR, Pandit AB (2008) Intensification of esterification of acids for synthesis of biodiesel using acoustic and hydrodynamic cavitation. Ultrason Sonochem 15 188-194... 

Esterification of acids with bulky substituents, such as 2,4,6-trimethyl-benzoic acid, can be achieved through formation of acyl cations. This is done by simply dissolving the carboxylic acid in strong sulfuric acid, whereby the acyl cation 11 is formed, and then pouring the solution into an excess of cold alcohol (see also Equations 18-5 and 18-6). This procedure works because it avoids the formation of a hindered tetrahedral intermediate similar to 10 and instead forms the conjugate acid directly ... 

The catalytic action of ChE s is, however, not limited to ester hydrolysis. Thus, these enzymes catalyze also the reverse reaction, i.e., esterification of acids with choline (14). They promote transesterification 15) and the condensation of hydroxylamine with acids 14) or esters 15). Anhydrides of carboxylic acids are also substrates of ChE s 16, 17) and can undergo all the reactions, mentioned with esters, i.e., hydrolysis, esterification, and hydroxamation. 

Product Extraction. The little used but very efficient method of using diphenyldia-zomethane for the extractive esterification of acidic materials from aqueous solution proved to be very effective [see footnote 93(c)]. 

The advantage of bidimensional representation is evident if four reactive components are involved, as in the class of reversible reactions A + B <-> C + D. This situation covers an important number of industrial applications, as the esterification of acids with alcohols. Selecting C as the reference, the transformed variables are XA = xA + xc, XB = xB + xc and XD = xD- xc since v, = 0. The transformed variables sums to one, but only two are used as co-ordinates. Accordingly, the pure components may be placed in the corner of a square diagram, reactants or products on the same diagonal. Figure A. 5 displays the reactive distillation map traced as before for the relative volatilities 4/2/6/1 and the equilibrium constant K t = 5. 

Dimethylformamide was suggested for the GC detection of microgram amounts of formic acid [182]. After esterification of acids with diazomethane the sample was treated with a dimethylamine—water mixture (1 2). Dimethylformamide was thus produced from formic acid ester, while other acids present were analysed as methyl esters. 

Esterification. The related salt dimethylchloroforminium chloride has been used for esterification (8, 186), but has the disadvantage that alkyl chlorides are also formed as by-products. The salt 1 does not activate an alcohol group and, in the presence of pyridine as base, it effects esterification of acids (even hindered ones) with primary and secondary alcohols in high yield. Esterification with hindered tertiary alcohols is possible, but slow. 

A.7.1 Esterification of Acids using Carbodiimides. The formation of anhydrides from carboxylic acids, thiocarboxylic acids, sulfonic acids and phosphorous acids are discussed in Section 2.4.S.2. In this section only special cases of anhydride formation are described. Mixed anhydrides of amino acids and adenylic acid are produced from the corresponding acids using DCC as the condensation agent. ° Mixed anhydrides not containing amino acids, such as butyryl adenate, adenosine 5 -phosphosulfate and p-nitrophenyl-thymidine-5-phosphate are also obtained. 

Alkylation of phenols, alcohols, amides, and acids. N-Alkylation of indoles and pyrroles by means of solid KOH in DMSO was reported a few years ago. Actually this method is applicable to a number of substrates. The substrate and alkyl halide are added to powdered KOH and stirred in DMSO, usually at 20°. Methyl-ation of phenols, alcohols, and amides occurs in high yield in about 5-30 minutes. Esterification of acids is slower. Dehydrohalogenation is a competing or predominating reaction when secondary or tertiary halides are used. Another limitation is that amino groups are converted into quaternary salts under these conditions. The general method can be used for permethylation of peptides. 

Ethyl 4 ntfiiffo-3,5 dinitrobenzoate gold-glimmering leaflets, mp 114°, It may be prepd by esterification of acid in ale HCl Ref Beil 14, 458... 

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