Esterification with higher alcohols

Aspartic acid and glutamic acid residues in wool can be esterified [13,242] using an alcohol and dilute hydrochloric acid. With methanol, esterification occurs at room temperature, but raised temperatures are needed for esterification with higher alcohols. 

Silica is heated with alcohols containing from two to eighteen carbon atoms to 190° (with primary alcohols) or 275° (with secondary alcohols). For small-chain alcohols an autoclave is used. Esterification with higher-boiling alcohols is achieved simply by refluxing while the water formed in the reaction is removed by azeotropic distillation. A small... 

Preferential esterification. Startg. tricarboxylic acid and Amberlyst 15 in methanol stirred at room temp, for 10 h monomethyl ester. Y 80%. a,p-Unsatd. and ar. carboxyl groups were left unaffected the method failed with higher alcohols (/-PrOH /-BuOH). Under these mild conditions, a-epimerization, c/5-tra 5-rearrangement, and transesterification (of ethyl esters) are avoided, and keto and olefinic groups remain intact. F.e. inch methyl esters of bile acids s. M. Petrini et al., Synth. Commun. 18, 847-53 (1988). 

It is interesting to note here that alternating ethylene-co-MA polymer after esterification with methyl alcohol is head-to-head poly(methyl acrylate)/ which cannot be prepared by conventional techniques. With the exception of glass transition (Tg) temperatures, the alternating ethylene-co-maleic ester copolymer is comparable to poly (methyl acrylate). The head-to-head polymer Tg is higher than the conventional head-to-tail poly(methyl acrylate). 

The free-radical-initiated copolymerization of trans-stilbene with MA was recently studied as a route to poly(methyl cinnamate). Alternating copolymers were prepared with specific viscosities, measured at 30°C in 0.5 NaOH (0.2g/100ml), as high as 1.40 dl/g. Esterification with methyl alcohol gave head-to-head (H-H) poly(methyl cinnamate). Even though H-H poly(methyl cinnamate) Tg was higher than head-to-tail (H-T) poly(methyl cinnamate), the H-H material had poorer stability than the H-T material. " """ ... 

The esters of sahcyhc acid account for an increasing fraction of the sahcyhc acid produced, about 15% in the 1990s. Typically, the esters are commercially produced by esterification of sahcyhc acid with the appropriate alcohol using a strong mineral acid such as sulfuric as a catalyst. To complete the esterification, the excess alcohol and water are distilled away and recovered. The cmde product is further purified, generally by distillation. For the manufacture of higher esters of sahcyhc acid, transestetification of methyl sahcylate with the appropriate alcohol is the usual route of choice. However, another reaction method uses sodium sahcylate and the corresponding alkyl hahde to form the desired ester. 

In this context, the esterification of 4-(l-pyrenyl)butyric acid with an alcohol to the corresponding ester was investigated [171]. Without the presence of sulfuric acid no reaction to the ester was foimd in the micro reactor. On activating the surface by a sulfuric acid/hydrogen peroxide mixture, however, a yield of 9% was achieved after 40 min at 50 °C. On making the surface hydrophobic by exposure to octadecyltrichlorosilane, no product formation was observed. Using silica gel in a laboratory-scale batch experiment resulted in conversion, but substantially lower than in the case of the micro reactor. The yield was no higher than 15% (40 min ... 

The rate enhancement for the esterification of benzoic acid with methanol was close to 100, when compared with the classical heating under reflux. On the other hand, the rate enhancement for the esterification with n-pentanol, using the same power level (560 W) was only 1.3. The approximate reaction temperature was almost the same for the two alcohols (134 °C and 137 °C respectively). It should be noted, however, that the rate enhancement for the esterification in pentanol increased to 6 times when a higher power level (630 W) was used, the reaction temperature being higher (162 °C). 

The most convenient methods to be used with silica having no pores or very wide ones are the reaction with thionyl chloride, the esterification with methanol or w-butanol and higher alcohols, and ion exchange, e.g., with uranyl ions (however, the general applicability of the latter reagent... 

Naoe et al. [239] used the sugar ester DK-F-110, a mixture of sucrose esters of fatty acids, as a nonionic surfactant along with isopropyl alcohol and hexane in a reverse micellar system to extract cytochrome C. This surfactant has a critical micellar concentration of 0.5 g/1 and HLB of 11. Aqueous phase pH was found to have a major role in the forward extraction and optimum extraction was achieved at pH 8.0. However, for optimum back extraction, addition of isopropyl alcohol at 20 vol.% was found to be very essential. Further, the esterification reaction rate of Rhizopus delemar lipase was found to be maximum in DK-F-110 systems and also higher than those obtained in AOT and lecithin-RMs at a water concentration of 0.25 mol l h... 

Pereira et al. (17) did not observe differences on acid conversion with alcohol varying between C4 and CIO in reactions performed with C. rugosa lipase immobilized on chitosan. However, Manjon et al. (23) working with M. miehei lipase immobilized on Celite verified that esterification yields decreased as the chain length of the acid or alcohol increased, with the alcohol length having a higher influence than the acid. 

The kinetics of the esterification of 1-octanol with hexanoic acid on zeolite BE A was studied by Nijhuis et al. [29], For the acid, a first-order behavior was found, whereas the alcohol showed a negative reaction order of -1. From the data, an Eley-Rideal mechanism was concluded. The acid adsorbs onto the surface of the catalyst and reacts with an alcohol. The adsorption of water, alcohol, ester or ether inhibits the reaction. Hoek [30] found that the adsorption constant of water is more than one order of magnitude higher than those of the other compounds. The rate law given by Nijhuis et al. [29] also includes the equilibrium limitation ... 

Esterification with alcohols in the presence of pyridine was used by Felder et al. [36]. Water produced in the reaction mixture is bound by the addition of N,N -dicyclohexyl-carbodiimide (Scheme 4.8). The acid (ca. 10 mequiv.) is dissolved in 25 ml of alcohol and 4 ml of pyridine and an excess of dicyclohexylcarbodiimide (12 mequiv.) are added (even more if the sample is not dry). The amount of pyridine can also be larger and it then acts as a solvent, e.g., if the alcohol used is solid (menthol). The mixture is then stirred at room temperature only with some higher alcohols or acids must the mixture be heated at 40—80°C for 30—120 min. If a precipitate of N,N -dicyclohexylurea is produced in the reaction, it is allowed to sediment and, after adding an internal standard,... 

Esters of fatty acids with monohydric alcohols find applications as emollients in cosmetics. They are prepared by acid- or base-catalyzed (trans)esterifications [200, 205]. As with biodiesel production, the use of enzymatic catalysis offers potential benefits but in the case of these specialty fatty acid esters there is a special advantage the products can be labelled as natural. Consequently, they command a higher price in personal care products where natural is an important customer-perceived advantage. Examples include the synthesis of isopropylmy-ristate by CaLB-catalyzed esterification [206] and n-hexyl laurate by Rhizomucor miehei lipase (Lipozyme IM-77)-catalyzed esterification [207] (see Fig. 8.38). 

Several chiral substituted a-phenyl-alkyl alcohols, which were partially enantio-merically enriched, were successfully purified by this method after esterification with 9-anthroic acid optical purities higher than 95% were obtained.Fluorescence studies of racemic compounds show a characteristic a-type excimer emission, whereas the chiral enantiomer exhibits a typical y-type monomer emission. Figure 7 shows the spectra of l-(2-chlorophenyl)ethyl 9-anthroate for a crystalline sample of enantiomeric (1) and racemic (2) at 77 K. It has been demonstrated that in the absence of configurational disorder chiral impurities in the range of 1 % can be detected by this method. ... 

Esterification and transesterification. Tetracyanoethylene used at about 10 mol% is the first Jt-acid catalyst for esterification of carboxylic acids with various alcohols. Transesterification requires higher temperature. 

The acid chloride is useful for the isolation of low-niellinit alcohols reaction in pyridine gives an ester of lower solubility and higher melting point. For example, vitamin D (m,p. 82-84°) from fish liver oil concentrates was isolated by esterification with 3,5-dinitrobenzoyl chloride, and purification by chromatography and crystallization as the 3J5-dinitrobenzoate, ra.p. 132°. ... 

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