Alkylation esterification

Alkylation is the addition of the alkyl group to an active functional group, formation of methyl esters being the most useful derivatisation reaction. A number of reagents are available but boron trifluoride in methanol is most commonly used. 

Other reagents commonly used include pentafluorobenzyl bromide developed for the analysis of acids, amides and phenols using an electron capture detector for enhanced sensitivity. Organics in surface waters have been successfully analysed by this procedure [47,48]. 

Dialkylacetals of DMF react instantaneously and quantitatively with acids, amines, amides, barbiturates either in solution or directly by on-column derivatisation using a mixture of the analyte and reagent. Methyl and butyl derivatives can be prepared. There is a considerable range of derivatisation reagents available and the reader is referred to the literature and the reference texts quoted [47-49]. In addition, many suppliers of 

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Methyl esterification of fatty acids with methanol is generally conducted in the presence of acid catalyst at an elevated temperature close to the boiling point of methanol. Recently, we found that fatty acids could be successfully methyl esterified in supercritical methanol without the use of a catalyst (10). In addition, from a comparative study between transesterification of vegetable oil and alkyl esterification of fatty acids with supercritical alcohols at 300°C in a batch-type reaction system, the reaction rates of alkyl esterification were found to be faster than those of transesterification (11). An additional finding was that alkyl esterification of fatty acids could be performed at a lower reaction temperature than transesterification. 

Biodiesel was prepared in various supercritical alcohol treatments with methanol, ethanol, 1-propanol, 1-butanol, or 1-octanol to study transesterification of rapeseed oil and alkyl esterification of fatty acid at temperatures of 300 and 350°C. The results showed that in transesterification, the reactivity was greatly correlated to the alcohol the longer the alkyl chain of alcohol, the longer the reaction treatment. In alkyl esterification of fatty acids, the conversion did not depend on the alcohol type because they had a similar reactivity. Therefore, the selection of alcohol in biodiesel production should be based on consideration of its performance of properties and economics. 

Index Entries Supercritical alcohol biodiesel fatty acids alkyl ester transesterification alkyl esterification. 

Alkylative esterification of 296 via the corresponding cesium salt with highly loaded Merrifield resin (3.4 mmol/g) resulted in polymer-bound o-azido ester 297.>31.132 Treatment of 297 with a fivefold excess of PPhj in THF at room temperature produced the corresponding... 

Alkylative esterification of carboxylic acids with alkyl halides are effected by action with TMG (1) [65]. An ester is given by the TMG (1) mediated reaction of y-hydroxy-a,p-unsaturated carboxylic acid with methyl iodide without lactone formation after isomerization [65a]. Barton s base effectively works in the alkylation of sterically hindered carboxylic acid [3]. Ethanolysis of the acetate of tertiary alcohol occurred easily in 86% yield in the presence of BTMG (2) [66] (Scheme 4.24). 

Isobe, T., Fukuda, K. and Ishikawa, T. (1998) Simple preparation of chiral l,3-dimethyl-2-iminoimidazolidines (monocyclic guanidines) and applications to asymmetric alkylative esterification. Tetrahedron Asymmetry, 9, 1729-1735. 

Carboxylic acids) (alkyl) Esterification -C03-CH3C,H5 -C03-CH3C,F3 2 ... 

Then, we wished to make use of the MW technique in the alkylating esterification of cyclic phosphinic acids such as l-hydroxy-3-phospholene oxides (7 and 8), 1-hydroxy-phospholane oxides (11 and 13), and 1,2,3,4,5,6-hexahydro-phosphinine oxide 15. The cyclic phosphinic acids 7,8,11,13, and 15 were reacted with a series of alkyl halides in the presence of K2CO3 under solvent-free and MW conditions (Scheme 7). It was foxmd that the application of TEBAC was beneficial, when alkyl halides with normal or decreased reactivity, such as ethyl iodide, n-propyl bromide, n-butyl bromide, and isopropyl bromide were the reactants. At the same time, when an alkyl halide with increased reactivity, such as benzyl bromide, was used, tiiere was no need for the catalyst [34,44,45]. 

SCHEME 7 Alkylating esterification of cydic phosphinic acids. 

E. Balint, E. Jablonkai, M. Balint, G. Keglevich, Alkylating esterification of l-hydroxy-3-phospholene oxides under solventless MW conditions, Heteroatom Chem. 21 (2010) 211-214. 

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