Fisher esterification

A. Do a Fisher esterification by refluxing 100 g 3,4,5-trimethoxybenzoic acid in ethanol with concentrated sulfuric acid for several hours. Cool, filter, to get the ester (I) (recrystallize-ethanol). 

The chemistry and procedures for modification of the - CO2H groups of PAA hyperbranched grafts on PE powder were analogous to those used for PAA grafts on PE or PP films and wafers. For example, a 90% yield in ester formation was possible using acid-catalyzed Fisher esterification. Likewise, quantitative reduction (ethyl chloroformate activation, borane-dimethyl sulfide reduction) to hyperbranched poly(allyl alcohol)s and amidation all could be carried out using procedures like those used for PAA/Au surfaces. 

Figure 6.5 Fisher esterification reaction using a continuous batch flow reactor.

Polyitaconic add is converted completdy to the methyl ester with diazomethane (7), while Fisher esterification results in partial esterification of both itaconic acid homo- and copolymers (6). DMI homopolymers and its copolymer with butadiene can be reduced with lithium aluminum hydride to the polymeric alcohols, which on the basis of solubility, may under some conditions be partially cross-linked by intermolecular ester formation (6). Hydrazine converts polydimethyl itaccmate to the polymeric dihydrazide which is water-soluble and exhibits reducing properties. The hydrazide can be treated with aldehyde or ketones to form polymeric hydrazones (45). A cross-linked polymer of bi chloroethyl ita-conate) on treatment with trietlylamine, has been converted by partial quatemization to an anion exchange resin (46). 

Chlorosulfonyl benzoates were synthesized from 2-aryldimethyloxazolines 17 (Scheme 5). Sequential treatment with n-butyllithium and dipropyl disulfide afforded sulfides 18. The oxazolines 18 were then hydrolyzed to the benzoic acids 19 under acidic conditions. Fisher esterification gave the esters 20, which were oxidized to the corresponding sulfonyl chlorides 21 using chlorine and aqueous acetic acid. When methoxy-substituted benzoic acids (19, X = OMe) were employed, further manipulations were performed prior to oxidation. For example, phenol (22) was prepared by demethylation with boron tribromide, subjected to esterification, and then alkylated by a variety of electrophiles to provide 23. As before, 23 was oxidized using chlorine and aqueous acetic acid. 

Figure 19.3 shows a general Fisher esterification reaction. Differently, Figure 19.4 shows a detailed reaction mechanism. 

Very polar carboxylic acids are esterified in esters before their analysis by GC-MS. In the Fisher esterification process, the reactive used is an alcohol, usually methanol or ethanol, which also has the role of solvent in the reaction. This reaction (Figure 1.4)... 

FIGURE 3.18 Protection of carboxyl groups by esterification of amino acids (A) by acid-catalyzed reaction with alcohol. [Curtius 1888, Fisher 1906] with X = Cl for H-Xaa-OMe, X-Xaa-OEt, and H-Pro-OCH2Ph ... 

Water concentrations in liquid and solid phases were measured by the Karl Fisher method using the Karl Fisher Titrator (Mettler DL 18). Butanol and butyl butyrate were determined by gas chromatography using a 6-ft, 5% DEGS on a Chromosorb WHP, 80/10 mesh column (Hewlett Packard, Palo Alto, CA) and hexanol as internal standard. Acid consumption was monitored by volumetric titration of samples diluted in ethanol employing 0.02 M KOH alcoholic solution and phenolphthalein as pH indicator. Esterification was expressed as molar percent of consumed reactant, according to Eq. 1 ... 

Kurlandsky SB, Duell EA, Kang S, Voorhees JJ, and Fisher GJ (1996) Auto-regulation of retinoic acid biosynthesis through regulation of retinol esterification in human keratinocytes./owrna/ of Biological Chemistry 271,15346-52. 

A number of reactions relevant to fine chemicals manufacture can be catalyzed by superacids, for example, dehydration of carboxamides to nitriles, Friedel-Crafts alkylation and acylation, Fisher indole synthesis of coumarins, isomerization of limonene, condensation of hydroquinone with aniline, and esterification in general (Hino and Arata, 1980, 1985 Joshi and Rajadhyaksha, 1980 Rajadhyak-sha and Chaudhari, 1987 Kumbhar and Yadav, 1989 Rajadhyaksha and Joshi, 1991 Kumbhar et al., 1994). Two particularly important reactions are described here. 

To determine whether CW has a catalytic effect of the resinification of FA, in a typical experiment, 0.75-1.0 phr freeze-dried CW was redispersed in FA by means of a brief ultrasonication treatment (Fisher 500W, 25-50% amphtude, 15 min bursts) followed by heating to 50 °C for additional dispersion. At 50 °C, the sulfonic acid residues are stable and de-esterification is not expected. After 1 h at 50 °C, the mixture was heated to the target reaction temperature untQ resinification of FA to PFA occurred. 

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