Ethyl mesitoate

Roberts and Whiting developed a method for effecting the anhydrous hydrolysis of esters and nitriles in DMSO. A solution of sodium methylsulfinylmethide is prepared from sodium hydride and DMSO and titrated with a solution of an appropriate amount of water in DMSO, using triphenylmethane as indicator. This produces a fine suspension of sodium hydroxide which hydrolyzes ethyl benzoate very rapidly at room temperature. As compared with reactions in hydroxylic solvents, rates are enhanced by a factor of 10 -10 . Benzonitrile is hydrolyzed to benzamide. Methyl and ethyl mesitoates are hydrolyzed readily at 25°. 

Esterification (4, 247). Shaw and Kunerth have reported further studies on the esterification of sodium salts of carboxylic acids with alkyl halides in HMPT at room temperature. The method is applicable to the preparation of ethyl esters of hindered acids for example, ethyl mesitoate can be obtained in 99% yield. In the esterification of acids that undergo ready decarboxylation, anhydrous potassium carbonate rather than NaOH is used as base (equation I). Diesters can be obtained by reaction of sodium salts of acids with dibromo-methane (equation II). Phenols are converted by this method into ethers in... 

Because of steric shielding, the hydrolysis of aromatic chlorinated esters and amides cannot be carried out under normal conditions, not even with the Hammett-Newman method, i.e. treatment with concentrated sulphuric acid and then with water. For comparison, the hydrolysis of highly hindered esters, such as ethyl mesitoate, can readily be performed in concentrated sulphuric acid (Treffers and Hammett, 1937 Newman et al., 1945). Hydrolysis of the perchlorinated esters can be effected with oleum in excellent yields. (To perform that of perchloroamides, hot (160°C) oleum is required (Ballester et al., 1978b).) It is assumed that the mechanism of hydrolysis for perchloroesters with oleum is analogous to that proposed by Newman, i.e. 

As in ester hydrolysis. Bender suggested that exchange takes place hy the addition of water to form a tetrahedral intermediate. The very slow exchange of mesitoic acid was attributed to steric hindrance or an ortho-effect by the ormethyl groups. The rate constant hydroi for the hydrolysis of the ethyl esters of these acids is two to four times greater than cxcii> fhe rate constant for 0 -exchange of the free acid. The difference is presumed to be due to the fact that the acid is more resonance-stabilized than the esters, although this is almost certainly not the only factor involved. 

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