Ester of carboxylic acids

If the nucleophilic oxygen atom of an alcohol attacks the carbonyl carbon atom of the carboxylic acid, the result is an ester that contains the oxygen atom of the alcohol. 

Water comes from here. Part of the original alcohol. 

As in the case of inorganic acids, a derivative of a carboxylic acid called an acid chloride or acyl chloride is often the preferred reagent to form esters. 

The reaction of an alcohol with an acid chloride produces an organic ester. The reaction releases HCl, which is neutralized with a base such as pyridine. 

This reaction, in which a halide ion is formally replaced by an alkoxy group, is an example of nucleophilic acyl substitution. A general representation of this mechanism using Nu as the nucleophile 

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Solid esters are easily crystallisable materials. It is important to note that esters of alcohols must be recrystallised either from non-hydroxylic solvents (e.g. toluene) or from the alcohol from which the ester is derived. Thus methyl esters should be crystallised from methanol or methanol/toluene, but not from ethanol, n-butanol or other alcohols, in order to avoid alcohol exchange and contamination of the ester with a second ester. Useful solvents for crystallisation are the corresponding alcohols or aqueous alcohols, toluene, toluene/petroleum ether, and chloroform (ethanol-free)/toluene. Esters of carboxylic acid derived from phenols... 

Just as waxes, fats, and oils are esters of carboxylic acids, phospholipids are diesters of phosphoric acid, H3PO4. 

Tertiary aliphatic alcohols Methyl esters of carboxylic acids Esters of n-chain carboxylic acids Silanes... 

Esters of aliphatic dibasic carboxylic acids Long-chain methyl esters of carboxylic acids... 

The reaction of step 2 is carried out by heating the reagents with various acid catalysts, such as orthophosphoric acid or its acid salts, bringing the pH down to 2.3-3.2 [4]. The Igepon A type of surfactant is quite susceptible to hydrolysis, particularly on the alkaline side, as is characteristic for most esters of carboxylic acids. It is therefore used most advantageously at a fairly neutral pH, such as combination soap-syndet toilet bars. 

Pyrolysis of Carboxylic Acids and Esters of Carboxylic Acids... 

Carbanions derived from optically active sulfoxides react with esters, affording generally optically active )S-ketoesters ° . Kunieda and coworkers revealed that treatment of (-t-)-(R)-methyl p-tolyl sulfoxide 107 with n-butyllithium or dimethy-lamine afforded the corresponding carbanion, which upon further reaction with ethyl benzoate gave (-l-)-(R)-a-(p-tolylsulfinyl)acetophenone 108. They also found that the reaction between chiral esters of carboxylic acids (R COOR ) and a-lithio aryl methyl sulfoxides gave optically active 3-ketosulfoxides The stereoselectivity was found to be markedly influenced by the size of the R group of the esters and the optical purity reached to 70.3% when R was a t-butyl group. 

Activated NHS esters of carboxylic acids are prepared by reacting the acid with NHS in the presence of DCC (Table 4, Figure 16). A-Hydroxysuccinimide esters are stable when kept under anhydrous and slightly acidic conditions, and they react rapidly with amino groups to form an amide in high yield. 

Benzyl esters of carboxylic acids are frequently used in organic synthesis for the protection of carboxyl groups. The C-O bond in benzyl esters can be cleaved more easily than the corresponding benzyl ether bond. The hydrogenolysis of an ester leads to carboxylic acid and toluene. Examples of debenzylation of benzyl esters of carboxylic acids on Pd/C catalysts are summarized in Table 4.4. 

In contrast to the reactions of the cycloamyloses with esters of carboxylic acids and organophosphorus compounds, the rate of an organic reaction may, in some cases, be modified simply by inclusion of the reactant within the cycloamylose cavity. Noncovalent catalysis may be attributed to either (1) a microsolvent effect derived from the relatively apolar properties of the microscopic cycloamylose cavity or (2) a conformational effect derived from the geometrical requirements of the inclusion process. Kinetically, noncovalent catalysis may be characterized in the same way as covalent catalysis that is, /c2 once again represents the rate of all productive processes that occur within the inclusion complex, and Kd represents the equilibrium constant for dissociation of the complex. 

Anhydro-D-glucose resulted, as mentioned, from the hydrolytic removal of a halogen atom at C6. Similar hydrolytic scission of sugar esters of carboxylic acids takes place without dehydration and with the liberation of the normal sugar. Thus, saponification of 6-benzoyl- or... 

An additional stabilization of the negative charge provided by the adjacent aryl group in aryllithiomethyl intermediates 400 makes l-(arylmethyl)benzotriazoles 399 attractive starting materials for many syntheses. Thus, reaction of anions 400 with esters of carboxylic acids leads to a-(benzotriazole-l-yl) ketones 401, which can be easily reduced to carbinols 402... 

The hydrogenolysis of the thiol esters of carboxylic acids offers a delicate method for reducing an acid to the corresponding aldehyde or alcohol application of this method to the sugar series has been made by Wolfrom and Karabinos who reduced D-ribonyl chloride tetraacetate (LXXV) to aldehydo-D-ribose tetraacetate (LXXVII) in 22% yield via ethyl thiol-D-ribonate tetraacetate (LXXVI). The desulfurization of the thiol ester (LXXVI) was carried out with a somewhat aged sample of Raney nickel" which doubtless had less activity than the... 

The napkthols are in many respects still more reactive than phenol. This is shown most distinctly by the fact that the naphthyl ethers can be obtained by the method used for the preparation of esters of carboxylic acids, namely, directly by the action of hydrogen chloride on the phenol in the presence of the alcohol. The naphthols, moreover, react readily with zinc-ammonium chloride and with ammonium sulphite and ammonia to yield naphthylamines. The second of these two methods is a general one. It was investigated by H. Bucherer. 

Variously N-substituted glycolamide esters (TV-substituted carbamoylmethyl esters) of carboxylic acids have been proposed as prodrugs of particular... 

In summary, (oxodioxolyl)methyl esters of carboxylic acid drugs appear to be generally useful as prodrugs. However, more studies are needed to document the structure-metabolism relationships, the relative contribution of enzymatic vs. nonenzymatic reactions in their in vivo activation, the reasons of some failures, their toxic potential, and their pharmacokinetic behavior in humans. 

N. M. Nielsen, H. Bundgaard, Prodrugs as Drug Delivery Systems. 68. Chemical and Plasma-Catalyzed Hydrolysis of Various Esters of Benzoic Acid A Reference System for Designing Prodrug Esters of Carboxylic Acid Agents , Int. J. Pharm. 1987, 39, 75-85. 

Reduction of esters of carboxylic acids is complex and takes place in stages and by different routes. In the first stage hydrogen adds across the carbonyl double bond and generates a hemiacetal (route a), or else it can hydrogenolyze... 

It has been reported ( ) that homogeneous ruthenium- or cobalt-iodide-based complexes catalyze the homologation of esters of carboxylic acid to their next higher homologues, for instance ... 

Aryl esters of carboxylic acids (X in general formula 1 = —COR,—COOR or —CONHR Section II). 

The reactivity of other nucleophiles is also of unusual interest. For example, F reacts efficiently with methyl esters of carboxylic acids without (3-hydrogens along an SN2 pathway (59) (Takashima and Riveros, 1978) to... 

It has been pointed out279 that the greater stability of a secondary phosphoric ester linkage relative to a primary linkage is analogous to the greater stability of secondary alkyl esters of carboxylic acids, rela-... 

Pyrolysis of Esters of Carboxylic Acids Hydro-acyloxy-elimination... 

The reactions catalyzed by Lewis acids are conducted for 10-20 hours at — 20 C to give hypochlorites in almost quantitative yield.82 Chlorine monofluoride activated by hydrogen fluoride to enhance its electrophilicity transforms the carbonyl function in esters of carboxylic acids to a difluoromethyl group. The reactions are carried out by passing 2molar equivalents of chlorine monofluoride gas through a solution of the ester in an equal volume of hydrogen fluoride at - 70 to - 30°C.83... 

Unless forcing conditions are applied, esters of carboxylic acids generally remain unaffected if they react, they give, depending on their structure, trifluoromethyl compounds or 1,1-difluoro ethers. 

Decarboxylation.1 Esters of carboxylic acids are converted to the corresponding nor-hydrocarbons by reaction with n-Bu3SnH in the presence of AIBN as radical initiator. The reaction involves fragmentation to RC02 followed by loss of COz to give R-, which is reduced to RH. Yields arc in the range 60 90%. 

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