From ester hydrolysis

Amides from Esters Hydrolysis of Ureides Hydrolysis of Carbamates Hydrolysis of Carboxamides Decarboxylation ... 

It is completely in line with overlap considerations that only the axial benzoate 202 is isolated from ester hydrolysis. TTie same holds for the hydrolytic fragmentation of acetal 203 [65]. 

The most widely used method for the preparation of carboxylic acids is ester hydrolysis. The esters are generally prepared by heterocyclization (cf. Chapter II), the most useful and versatile of which is the Hantzsch s synthesis, that is the condensation of an halogenated a- or /3 keto ester with a thioamide (1-20). For example ethyl 4-thiazole carboxylate (3) was prepared by Jones et al. from ethyl a-bromoacetoacetate (1) and thioformamide (2) (1). Hydrolysis of the ester with potassium hydroxide gave the corresponding acid (4) after acidification (Scheme 1). 

Nucleophilic acyl substitutions at the ester carbonyl group are summarized m Table 20 5 on page 849 Esters are less reactive than acyl chlorides and acid anhydrides Nude ophilic acyl substitution m esters especially ester hydrolysis has been extensively mves tigated from a mechanistic perspective Indeed much of what we know concerning the general topic of nucleophilic acyl substitution comes from studies carried out on esters The following sections describe those mechanistic studies... 

When esterification is the objective water is removed from the reaction mixture to encourage ester formation When ester hydrolysis is the objective the reaction is carried out m the presence of a generous excess of water Both reactions illustrate the applica tion of Le Chatelier s principle (Section 6 10) to organic synthesis... 

Convincing evidence that ester hydrolysis in base proceeds by the second of these two paths namely nucleophilic acyl substitution has been obtained from several sources In one experiment ethyl propanoate labeled with 0 m the ethoxy group was hydrolyzed On isolating the products all the 0 was found m the ethyl alcohol there was no 0 enrichment m the sodium propanoate... 

The saponification of 0 labeled ethyl propanoate was desenbed in Section 20 11 as one of the significant expenments that demonstrated acyl-oxygen cleavage in ester hydrolysis The 0 labeled ethyl propanoate used in this expenment was prepared from 0 labeled ethyl alcohol which in turn was obtained from acetaldehyde and 0 enriched water Wnte a senes of equations... 

Acidic Cation-Exchange Resins. Brmnsted acid catalytic activity is responsible for the successful use of acidic cation-exchange resins, which are also soHd acids. Cation-exchange catalysts are used in esterification, acetal synthesis, ester alcoholysis, acetal alcoholysis, alcohol dehydration, ester hydrolysis, and sucrose inversion. The soHd acid type permits simplified procedures when high boiling and viscous compounds are involved because the catalyst can be separated from the products by simple filtration. Unsaturated acids and alcohols that can polymerise in the presence of proton acids can thus be esterified directiy and without polymerisation. 

Three general methods exist for the resolution of enantiomers by Hquid chromatography (qv) (47,48). Conversion of the enantiomers to diastereomers and subsequent column chromatography on an achiral stationary phase with an achiral eluant represents a classical method of resolution (49). Diastereomeric derivatization is problematic in that conversion back to the desired enantiomers can result in partial racemization. For example, (lR,23, 5R)-menthol (R)-mandelate (31) is readily separated from its diastereomer but ester hydrolysis under numerous reaction conditions produces (R)-(-)-mandehc acid (32) which is contaminated with (3)-(+)-mandehc acid (33). 

Expect some product contamination if feed components can react with water, eg, ester will be partially hydrolyzed to acid and alcohol fate of reaction product species depends on above rules, eg, methanol from methyl ester hydrolysis probably not stripped out of bottoms stream. 

Poly(vinyl alcohol) can be derived from the hydrolysis of a variety of poly(vinyl esters), such as poly(vinyl acetate), poly(vinyl formate), and poly(vinyl ben2oate), and of poly(vinyl ethers). However, all commercially produced poly(vinyl alcohol) is manufactured by the hydrolysis of poly(vinyl acetate). The manufacturing process can be viewed as one segment that deals with the polymeri2ation of vinyl acetate and another that handles the hydrolysis of poly(vinyl acetate) to poly(vinyl alcohol). 

The possible presence in the 4-chloro-4-hexenyl trifluoroacetate of small amounts of two cis-trans pairs of products of addition of trifluoroacetic to the triple bond without concomitant halogen shift remains speculative. In any event these compounds would be removed as ketones upon hydrolysis of the trifluoroacetate. Both the 4-chloro-4-hexenyl trifluoroacetate and the alcohol resulting from its hydrolysis have been shown to contain 9% of the (E) isomer. In the present study the hydrogen decoupled magnetic resonance spectra of the ester and alcohol were shown to contain peaks attributable to approximately 9% of E) isomer. 

This variation from the ester hydrolysis mechanism also reflects the poorer leaving ability of amide ions as compared to alkoxide ions. The evidence for the involvement of the dianion comes from kinetic studies and from solvent isotope effects, which suggest that a rate-limiting proton transfer is involved. The reaction is also higher than first-order in hydroxide ion under these circumstances, which is consistent with the dianion mechanism. 

Polymer derived from the hydrolysis of polyvinyl esters. 

Group of plastics composed of resins derived from the hydrolysis of polyvinyl esters or copolymers of vinyl esters. 

Taft began the LFER attack on steric effects as part of his separation of electronic and steric effects in aliphatic compounds, which is discussed in Section 7.3. For our present purposes we abstract from that treatment the portion relevant to aromatic substrates. Hammett p values for alkaline ester hydrolysis are in the range +2.2 to +2.8, whereas for acid ester hydrolysis p is close to zero (see Table 7-2). Taft, therefore, concluded that electronic effects of substituents are much greater in the alkaline than in the acid series and. in fact, that they are negligible in the acid series. This left the steric effect alone controlling relative reactivity in the acid series. A steric substituent constant was defined [by analogy with the definition of cr in Eq. (7-22)] by Eq. (7-43), where k is the rate constant for acid-catalyzed hydrolysis of an orr/to-substituted benzoate ester and k is the corresponding rate constant for the on/to-methyl ester note that CH3, not H, is the reference substituent. ... 

The Zincke reaction has also been adapted for the solid phase. Dupas et al. prepared NADH-model precursors 58, immobilized on silica, by reaction of bound amino functions 57 with Zincke salt 8 (Scheme 8.4.19) for subsequent reduction to the 1,4-dihydropyridines with sodium dithionite. Earlier, Ise and co-workers utilized the Zincke reaction to prepare catalytic polyelectrolytes, starting from poly(4-vinylpyridine). Formation of Zincke salts at pyridine positions within the polymer was achieved by reaction with 2,4-dinitrochlorobenzene, and these sites were then functionalized with various amines. The resulting polymers showed catalytic activity in ester hydrolysis. ... 

The reasonable mechanism outlined above has not yet been rigorously proven in every detail, but is supported by the fact that a 1 1-intermediate 5 has been isolated." The ester groups are essential for the Weiss reaction because of the /3-keto ester functionalities however, the ester groups can be easily removed from the final product by ester hydrolysis and subsequent decarboxylation. 

Discussion. For oils and fats, which are esters of long-chain fatty acids, the saponification value (or number) is defined as the number of milligrams of potassium hydroxide which will neutralise the free fatty acids obtained from the hydrolysis of 1 g of the oil or fat. This means that the saponification number is inversely proportional to the relative molecular masses of the fatty acids obtained from the esters. A typical reaction from the hydrolysis of a glyceride is ... 

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