Esters => carboxylic acids

The action of esterases consists essentially in the hydrolysis (or synthesis) of carboxylic acid esters according to the equation ... 

Inspired by the many hydrolytically-active metallo enzymes encountered in nature, extensive studies have been performed on so-called metallo micelles. These investigations usually focus on mixed micelles of a common surfactant together with a special chelating surfactant that exhibits a high affinity for transition-metal ions. These aggregates can have remarkable catalytic effects on the hydrolysis of activated carboxylic acid esters, phosphate esters and amides. In these reactions the exact role of the metal ion is not clear and may vary from one system to another. However, there are strong indications that the major function of the metal ion is the coordination of hydroxide anion in the Stem region of the micelle where it is in the proximity of the micelle-bound substrate. The first report of catalysis of a hydrolysis reaction by me tall omi cell es stems from 1978. In the years that... 

Many compounds contain more than one functional group Prostaglandin Ei a hormone that regulates the relaxation of smooth muscles con tains two different kinds of carbonyl groups Classify each one (aldehyde ketone carboxylic acid ester amide acyl chloride or acid anhydride) Identify the most acidic proton in prostaglandin Ei and use Table 1 7 to estimate its pK ... 

Conversions of acid anhydrides to other carboxylic acid derivatives are illustrated m Table 20 2 Because a more highly stabilized carbonyl group must result m order for nucleophilic acyl substitution to be effective acid anhydrides are readily converted to carboxylic acids esters and amides but not to acyl chlorides... 

Carboxylic acid esters Carboxylic acid groups... 

Carboxylic acid hydiazides are prepared from aqueous hydrazine and tfie carboxylic acid, ester, amide, anhydride, or halide. The reaction usually goes poody with the free acid. Esters are generally satisfactory. Acyl halides are particularly reactive, even at room temperature, and form the diacyl derivatives (22), which easily undergo thermal dehydration to 1,3,4-oxadiazoles (23). Diesters give dihydtazides (24) and polyesters such as polyacrylates yield a polyhydrazide (25). The chemistry of carboxyhc hydrazides has been reviewed (83,84). 

Carboxylic Acid Esters. In the carboxyflc acid ester series of surfactants, the hydrophobe, a naturally occurring fatty acid, is solubilized with the hydroxyl groups of polyols or the ether and terminal hydroxyl groups of ethylene oxide chains. 

Chromone-5-carboxylic acid, 7-hydroxy-2-methyl-decarboxylation, 3, 711 Chromonecarboxylic acids decarboxylation, 3, 710 Chromone-2-carboxylic acids esters... 

Isoxazole-4-carbaldehyde, 6, 84 Isoxazole-4-carbaldehyde, 5-methyl-3-phenyl-oxidation, 6, 27, 53 Isoxazole-5-carbaldehyde synthesis, 6, 84 Isoxazole-3-carboxylic acid esters... 

PERKIN Carboxylic Acid (Ester) Synthesis Synthesis of cycloalkane cartxixylic acids Irom o,ci>-dihaloalkanes and diethyl sodiummalonate. 

Notice in the list of Lewis bases just given that some compounds, such as carboxylic acids, esters, and amides, have more than one atom ivith a lone pair of electrons and can therefore react at more than one site. Acetic acid, for example, can be protonated either on the doubly bonded oxygen atom or on the singly bonded oxygen atom. Reaction normally occurs only once in such instances, and the more stable of the two possible protonation products is formed. For acetic add, protonation by reaction with sulfuric acid occurs on... 

Note that the diorganocopper reaction occurs only with acid chlorides. Carboxylic acids, esters, acid anhydrides, and amides do not react with lithium diorganocopper reagents. 

Most carbonyl compounds exist almost exclusively in the keto form at equilibrium, and it s usually difficult to isolate the pure enol. For example, cyclohexanone contains only about 0.0001% of its enol tautomer at room temperature, and acetone contains only about 0.000 000 1% enol. The percentage of enol tautomer is even less for carboxylic acids, esters, and amides. Even though enols are difficult to isolate and are present only to a small extent at equilibrium., they are nevertheless responsible for much of the chemistry of carbonyl compounds because they are so reactive. 

HO A phosphoric acid monoester HO A phosphoric acid diester 0 1 R" A phosphoric acid triester A carboxylic acid ester... 

Distinguish between alcohols, ethers, aldehydes, ketones, carboxylic acids, esters, and amines. (Example 22.6 Problems 15-18) 16,18... 

Classify each of the following as a carboxylic acid, ester, and/or alcohol. 

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