Acetic acid, esterification with

Esterification. Extensive commercial use is made of primary amyl acetate, a mixture of 1-pentyl acetate [28-63-7] and 2-metliylbutyl acetate [53496-15-4]. Esterifications with acetic acid are generally conducted in the Hquid phase in the presence of a strong acid catalyst such as sulfuric acid (34). Increased reaction rates are reported when esterifications are carried out in the presence of heteropoly acids supported on macroreticular cation-exchange resins (35) and 2eohte (36) catalysts in a heterogeneous process. Judging from the many patents issued in recent years, there appears to be considerable effort underway to find an appropriate soHd catalyst for a reactive distillation esterification process to avoid the product removal difficulties of the conventional process. 

Gas chromatographic separation has not gained wide acceptance in spite of being quite sensitive and specific. This mode of separation is complicated by the necessity for derivatization of anticoccidials before analysis. The hydroxy metabolite of dimetridazole is subjected to derivatization via esterification with acetic acid/sulftiric acid mixture (402), while lasalocid is derivatized via silylation with N,0-Bis(trimethylsilyl)trifiuoroacetamide (BSTFA) (387). This derivatization step is required not only to form the volatile derivatives of these drugs but also to improve their chromatographic properties (thermal stability and decreased polarity). 

The first reaction step is most probably hydrolysis of the aryl methyl ether by hydrobromic and acetic acid. Such a mixture is very efficient because one of the products, methanol, is continuously removed from the reaction mixture by esterification with acetic acid, and thus the reaction equilibrium between the starting material and the product is shifted toward the product. 

Surprisingly, there is limited nonproprietary experimental data on methanol esterification with acetic acid (29). Studies have been confined to liquid-phase systems distant from equilibrium (30), in regions where hydrolysis is unimportant. A physical study of the ternary methanol—methyl acetate—water system is useful for design work (31). Methyl acetate and methanol form an azeotrope which boils at 53.8°C and contains 18.7% alcohol An apparent methanol—water azeotrope exists, boiling at 64.4°C and containing about 2.9% water. These azeotropes seriously complicate methyl acetate recovery. Methyl acetate is quite soluble in water, and very soluble in water—methanol mixtures, hence two liquid phases suitable for decanting are seldom found. 

Formation of 3-MHA occurs thorough a more complex mechanism, that involves first liberation of 3-MH from the cysteinyl-conjugate precursor, followed by yeast-driven esterification with acetic acid (Fig 8D.10). The formation of 3-MHA from 3-MH occurs through the same pathway leading to the formation of acetate esters, since over expression of the alcohol acetyltransferase gene ATFl increased formation and overexpression of esterase gene lAHl decreased formation (Swiegers et al. 2006). 3-MH can also form chemically by reaction between H2S produced by the yeast and carbonyl compounds present in the must, such as 2-hexenal. This pathway only accounts for 10% of the 3-MH typically formed in fermentation (Schneider et al. 2006). 

FIGURE 10.23 (See color insert following page 588.) Ethanol esterification with acetic acid comparison performances of different... 

Acetic anhydride is used in the manufacture of cellulose acetate-based film, cigarette filters, and plastics. Eastman Chemical developed a process that is based on gasification of coal in a Texaco gasifier to make synthesis gas which then is converted to methanol. The methanol is converted to methyl acetate by esterification with acetic acid and then carbonylated. The carbonylation process uses rhodium salt catalysts with ligands and an iodine promoter [30]. 

Process aspects Tor extraction ofaceiic acid with amines arc discussed by Rickard al.11 Alcohol diluents gave the highest values of Kd. but the alcohols were subject to esterification with acetic acid upon regeneration by distillation. Ketones appeared to be satisfactory diluents from the standpoint of high KD. Chloroform is a superior diluent because il is a Lewis acid and can interact with the complex.4 However, chloroform is toxic, and this fact may limit its use. 

A similar favourable effect has been seen with 16a-OH by esterification with acetic acid (35->79, 48- 80) or nitric acid (35 81,... 

Cellulose acetate (CA), cellulose acetobutyrate (CAB) cellulose propionate (CP), Thermoplastics manufactured from cellulose by esterification with acetic acid (CA), acetic acid and butyric acid (CAB), or propionic acid (CP). Their products are characterized by high impact strength, transparency (without filler), and oil resistance. Examples of applications consumer goods, toys, combs, keys for music instruments and business machines, spectacle frames, photographic films. CA fibres are used for underwear, neckties, etc. Trade names Cellidor (FRG), Setilithe (B), Tenite (USA). 

Food-grade emulsifiers are esters of edible fatty acids originating from animal or vegetable sources and polyvalent alcohols like glycerol, propylene glycol, sorbitol, and sucrose [75], These products can be modified by making derivatives with ethylene oxide or by esterification with acetic acid, diacetyl tartaric acid, succinic acid, citric acid, or lactic acid, which makes it possible to tailor-make surface-active materials with specific properties [75],... 

Citrates have been used as PVC plasticizers in specialty applications for about 60 years. Citrate esters are prepared by the esterification of citric acid with three molar equivalents of synthetic n-butanol. As this step does not convert the hydroxyl group of the citric acid, and the free hydroxyl group can create long-term compatibility problems, the hydroxyl group needs to be converted to an ester in a separate step. This is accomplished through esterification with acetic acid or acetic anhydride. 

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