Organic chemistry esters

Many of the important enzyme-catalyzed reactions are similar to the reactions we studied in the chapters on organic chemistry ester hydrolysis, alcohol oxidation, and so on. However, laboratory conditions cannot match what happens when these reactions are carried ont in the body enzymes canse snch reactions to proceed under mild pH and temperature conditions. In addition, enzyme catalysis within the body can accomplish in seconds reactions that ordinarily take weeks or even months under laboratory conditions. 

In organic chemistry the term is used to describe the conversion of an ester to an acid and an alcohol (saponification), the addition of the elements of water to a molecule, e.g. the conversion of a nitrile to an amide... 

This reaction is used in organic chemistry to separate an aldehyde from, for example, an ester. 

Some esters of inorganic acids such as dimethyl sulfate are used as reagents m syn thetic organic chemistry Certain naturally occurring alkyl phosphates play an important role m biological processes... 

The present chapter extends our study of carbanions to the enolate ions derived from esters Ester enolates are important reagents m synthetic organic chemistry The stabilized enolates derived from p keto esters are particularly useful... 

Carey Organic Chemistry I 21 Ester Enolates Fifth Edition... 

In the first century of "organic" chemistry much attention was given to the structures of carbogens and their transformations. Reactions were classified according to the types of substrates that underwent the chemical change (for example "aromatic substitution," "carbonyl addition," "halide displacement," "ester condensation"). Chemistry was taught and learned as transformations characteristic of a structural class (e.g. phenol, aldehyde) or structural subunit... 

A vast variety of perfluoroalkanesulfonic esters are known, and their application in synthetic organic chemistry is increasing rapidly (for a comprehensive review, see reference 66) These compounds are readily available by the reaction of organic halides with silver perfluoroalkanesulfonate or by the reaction of an alcohol with the corresponding perfluoroalkanesulfonic anhydride or chloride Alkyl per-fluoroalkanesulfonates are powerful alkylating reagents because of the excellent... 

The mechanisms by which transition-metal oxidizing agents convert alcohols to aldehydes and ketones are complicated with respect to their inorganic chemistry. The organic chemistry is clearer and one possible mechanism is outlined in Figure 15.4. The key intennediate is an alkyl chromate, an ester of an alcohol and chromic acid. 

Anions of (3-keto esters are said to be synthetically equivalent to the enolates of ketones. The anion of ethyl acetoacetate is synthetically equivalent to the enolate of acetone, for example. The use of synthetically equivalent groups is a common tactic in synthetic organic chemistry. One of the skills that characterize the most creative practitioners of organic synthesis is an ability to recognize situations in which otherwise difficult transfonnations can be achieved through the use of synthetically equivalent reagents. 

Nucleophilic substitution of the halogen atom of halogenomethylisoxazoles proceeds readily this reaction does not differ essentially from that of benzyl halides. One should note the successful hydrolysis of 4-chloromethyl- and 4-(chlorobenzyl)-isoxazoles by freshly precipitated lead oxide, a reagent seldom used in organic chemistry. Other halides, ethers, and esters of the isoxazole series have been obtained from 3- and 4-halogenomethylisoxazoles, and 3-chloro-methylisoxazole has been reported in the Arbuzov rearrangement. Panizzi has used dichloromethylisoxazole derivatives to synthesize isoxazole-3- and isoxazole-5-aldehydes/ ... 

Alcohols occupy a central position in organic chemistry. They can be prepared from many other kinds of compounds (alkenes.. alkyl halides, ketones, esters, and aldehydes, among others), and they can be transformed into an equally wide assortment of compounds (Figure 17.3). 

Organic chemists have been aware of reversible addition-fragmentation involving xanthate esters in organic chemistry for some time. It is the basis of the Barton-McCombie process for deoxygenation of alcohols (Scheme 9.37).402 404... 

A reaction which has proved to be of much use in synthetic organic chemistry is the formation of the ortho and/or the para isomers of a hydroxyketone (CVI and CVTI) by treatment of a phenolic ester (CV) with an acid catalyst, viz. 

The strategy described here explains the different possibilities of enzymatic ammonolysis and aminolysis reaction for resolution of esters or preparation of enantiomerically pure amides, which are important synthons in organic chemistry. This methodology has been also applied for the synthesis of pyrrolidinol derivatives that can be prepared via enzymatic ammonolysis of a polyfunctional ester, such as ethyl ( )-4-chloro-3-hydroxybutanoate [30]. In addition, it is possible in the resolution of chiral axe instead of a stereogenic carbon atom. An interesting enzymatic aminolysis of this class of reaction has been recently reported by Aoyagi et al. [31[. The side chain of binaphthyl moiety plays an important role in the enantiodis-crimination of the process (Scheme 7.14). 

The atom economy for this process is 86.5% (100 X 116/134), which is reasonable. To calculate the E-factor and EMY further information is needed. From published literature (Vogel s Practical Organic Chemistry ), a standard procedure is to mix butanol (37 g) with glacial acetic acid (60 g), and a small amount of sulfuric acid catalyst (ignored in all calculations). Following completion of the reaction the mixture is added to water (250 g). The crude ester is washed further with water (100 g), then saturated sodium bicarbonate solution (25 g) and finally water (25 g). After drying over 5 g of anhydrous sodium sulfate the crude ester is distilled to give product (40 g) in a yield of 69%. 

In classical organic chemistry, nltrosamlnes were considered only as the reaction products of secondary amines with an acidified solution of a nitrite salt or ester. Today, it is recognized that nitrosamines can be produced from primary, secondary, and tertiary amines, and nltrosamides from secondary amides. Douglass et al. (34) have published a good review of nitrosamine formation. For the purposes of this presentation, it will suffice to say that amine and amide precursors for nitrosation reactions to form N-nitroso compounds are indeed ubiquitous in our food supply, environment, and par-... 

The Baeyer-Villiger oxidation reaction was discovered more than 100 years ago by Adolf von Baeyer and Victor Villiger. By this reaction, ketones are converted into the corresponding esters. In organic chemistry, peracids are commonly used as catalyst to perform this atypical oxidation reaction that results in oxygen insertion into a carbon—carbon bond (Fig. 1). 

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