Esterification during

Minguez-Mosquera M.I. and Hornero-Mendez, D., Changes in carotenoid esterification during the fruit ripening of Capsicum annuum cv. Bola. J. Agric. Food Chem., 42, 640,1994. 

The 0-[(methylthio)thiocarbonyl]ceUulose prepared by Rogovin is much more sensitive toward boiling water than its O-(methoxycarbonyl) analog, suffering 70-75% de-esterification during 8 hours, whereas the latter is unchanged. 

P2 is a component of myelin from the peripheral nervous system. It is localized on the cytoplasmic side of Schwann cells where it behaves as peripheral membrane protein, although a small amount is found in the cytoplasm (Trapp et al., 1984). Like the other iLBPs, the exact biochemical role of P2 is unknown. Its cellular localization and its ability to bind different fatty acids and retinoids (Uyemura et al., 1984) suggest that it may function in fatty acid trafficking. It would therefore play a major role in the movement of fatty acids between the site of uptake and that of esterification during the massive phospholipid synthesis phase of myelinating Schwann cells. 

An auxin in apple endosperm (565) not identical with indoleacetic acid was identified as ethyl indoleacetate (863, cf. 697), but this may be an artifact due to esterification during isolation (377). 

Esters in wine have two distinct origins enzymic esterification during the fermentation process and chemical esterification during long-term aging. The same esters may be synthesized in either way. 

The structural evolution of the nanocomposites upon thermal treatment is very interesting, as formation of the alloy takes place concurrently with crystallization and phase transition of the alumina matrix. Pure AI2O3 aerogels obtained by this procedure exhibited a layered pseudo-boehmite structure (in particular, the ethyl derivative of boehmite was formed as a consequence of esterification during supercritical drying), which upon thermal treatment was converted to nanocrystalline 7-AI2O3, and finally at 1,000°C, the thermodynamically stable polymorph a-Al203 started to crystallize. 

Two pathways for arterial cholesterol esterification have been claimed, direct esterification with acyl-CoA and transesterification via a tissue LCAT. The remarkable increase in the acyl CoA-dependent esterification during atherogenesis suggests that the former reaction is of substantially greater significance.20 Both the enhanced rate (28-40 fold) of cholesterol esterification in the atherosclerotic intima and the greater permeability of LP cholesterol ester into atherosclerotic lesions suggest that these processes may cause the observed accumulation of cholesterol esters. 

Gas-chromatographic methods are widely used to analyze amino acids in the hydrolyzates of small protein samples. The method s sensitivity is the major reason for these applications. In addition, GC-based techniques provide opportunities to distinguish and quantitate amino acids (and several other compound types) as different optical isomers. The most popular procedure to separate R and S isomers employs an optically active (chiral) stationary phase. Because of the zwitterionic nature of amino acids, a two-step derivatization is necessary prior to GC. As the first step, the acid (carboxy) function is blocked through esterification. During the second treatment, the amino groups are acylated. Figure 16 demonstrates... 

The answer to this question is critical because it tells us whether the carbon-oxygen bond of the alcohol or a carbon-oxygen of the carboxylic acid is broken during esterification... 

The results of the Roberts-Urey experiment tell us that the C—O bond of the alco hoi IS preserved during esterification The oxygen that is lost as a water molecule must come from the carboxylic acid... 

Acryflc acid, alcohol, and the catalyst, eg, sulfuric acid, together with the recycle streams are fed to the glass-lined ester reactor fitted with an external reboiler and a distillation column. Acrylate ester, excess alcohol, and water of esterification are taken overhead from the distillation column. The process is operated to give only traces of acryflc acid in the distillate. The bulk of the organic distillate is sent to the wash column for removal of alcohol and acryflc acid a portion is returned to the top of the distillation column. If required, some base may be added during the washing operation to remove traces of acryflc acid. 

Emissions During Plasticizer Production and Distribution. Phthalate plasticizers are produced by esterification of phthaUc anhydride in closed systems hence losses to atmosphere are minimal. Inquiries of all the principal plasticizer producers indicate a maximum total emission in Western Europe of 220 t/yr, 90% of which is to the water compartment. This level is expected to decrease in the future due to increa sing plant water treatment. 

Uses ndReactions. Linalool can be estetified to linalyl acetate by reaction with acetic anhydride. Linalyl acetate [115-95-7] has a floral-fmity odor, reminiscent of bergamot and lavender. The price of the acetate in 1995 was 14.30/kg (45). Linalool is subject to dehydration and to isomerization to nerol and geraniol during the esterification. However, if the acetic acid formed during the esterification is removed in a distillation column, the isomerization can be minimized and good yields of the acetate obtained (130). 

A series of sorbitol-based nonionic surfactants are used ia foods as water-ia-oil emulsifiers and defoamers. They are produced by reaction of fatty acids with sorbitol. During reaction, cycHc dehydration as well as esterification (primary hydroxyl group) occurs so that the hydrophilic portion is not only sorbitol but also its mono- and dianhydride. The product known as sorbitan monostearate [1338-41 -6] for example, is a mixture of partial stearic and palmitic acid esters (sorbitan monopalmitate [26266-57-9]) of sorbitol, 1,5-anhydro-D-glucitol [154-58-8] 1,4-sorbitan [27299-12-3] and isosorbide [652-67-5]. Sorbitan esters, such as the foregoing and also sorbitan monolaurate [1338-39-2] and sorbitan monooleate [1338-43-8], can be further modified by reaction with ethylene oxide to produce ethoxylated sorbitan esters, also nonionic detergents FDA approved for food use. 

Pentaerythritol with its four primary hydroxyl groups is used for the preparation of tetraesters and presents Httie difficulty except for its high melting point of 263°C, when pure. Pentaerythritol tetraesters are used in aircraft lubes, synthetic drying oils, and alkyds. Esters derived from trimethylo1 alkanes and dipentaerythritol are also used in alkyd resins (qv). Esterification may take place in situ during preparation of the alkyd. 

The acid chlorides are generally more reactive than the corresponding acid anhydrides. In fact, the alcoholysis of acid chlorides is probably the best laboratory method for preparing esters. Frequentiy, basic materials are added during the course of the reaction to neutralize by-product hydrochloric acid. When the basic material is aqueous caustic, the procedure is referred to as the Schotten-Baumann procedure (73). Esterification of tertiary alcohols by acid chlorides is described in Reference 74. Esters of tertiary alcohols can also be formed through an intermediate /-butyl thioate group (75) ... 

Ethyl acetate is made industrially by both batch and continuous processes (361,362). Glacial acetic acid is commonly the starting material, and any water formed during the esterification has to be removed. Sulfuric acid may be added periodically to the reactor to replace the acid lost in side reactions. 

Two isomers, a solid and a liquid, are formed during the bromination and subsequent esterification. 

Laminating resins have been offered by Akzo (Diacryl 101), Dow (Derakane Vinyl Esters) and Showa (Spilac). Typical of these is Diacryl 101, which is manufactured by esterification of the addition product of ethylene oxide to bis-phenol A with methacrylic acid. They exhibit lower curing shrinkage than the polyester laminating resins during cure. The structure of Diacryl 101 is... 

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