2.3.6- Trimethylbenzoic acid

Usually, in situ preparation in Barbier-type carbonyl additions are carried out with the bromides or chlorides even sterically blocked carboxylates, such as 2,4,6-trimethylbenzoic acid esters, can be used successfully15. The reactions are accelerated by ultrasound16,17. 

The other mechanism involving acyl cleavage is the AacI mechanism. This is rare, being found only where R is very bulky, so that bimolecular attack is sterically hindered, and only in ionizing solvents. The mechanism has been demonstrated for esters of 2,4,6-trimethylbenzoic acid (mesitoic acid). This acid depresses the freezing point of sulfuric acid four times as much as would be predicted from its molecular weight, which is evidence for the equilibrium... 

The kinetics of the acid-catalyzed esterification reaction of 2,4,6-trimethylbenzoic acid in i-PrOH under microwave irradiation have been investigated [84], A simple and practical technique for MW-assisted synthesis of esters has been reported wherein the reactions are conducted either on solid mineral supports or by using a phase transfer catalyst (PTC) in the absence of organic solvents [85], The esterification of enols with acetic anhydride and iodine has also been recorded [86],... 

Saponification of esters of 2,4,6-trimethylbenzoic acid with potassium hydroxide complex of dicyclohexyl-1 S-crown-fi0,4... 

Pedersen (1) noted that the sterically hindered esters of 2, 4, 6-trimethylbenzoic acid, although resistant to saponification by KOH in hydroxylic solvents, are saponified by the KOH complex of dicyclohexyl-18-crown-6 in aromatic hydrocarbons. 

Trimethylbenzoic acid (mesitoic acid) [480-63-7] M 164.2, m 155°. Crystd from water, ligroin or carbon tetrachloride [Ohwada et al. JACS 108 3029 1986. ... 

The important reactions of protonated acids and esters were deduced many years ago, largely on the basis of the anomalous cryoscopic behaviour of a few compounds. Treffers and Hammett5, while extending the work of Hantzsch4 on cryoscopic measuremnets in concentrated sulphuric acid, found that 2,4,6-trimethylbenzoic acid gives an / -value of 4, twice the usual figure. The only reasonable interpretation of this result was in terms of an ionization, as proposed by Hantzsch to account for the similar behaviour of triphenylcarbinol, viz. 

Trimethylbenzoic acid has two methyl groups ortho to the carboxylic acid functional group. These bulky methyl groups block the approach of the alcohol and prevent esterification from occurring under Fischer esterification conditions. A possible route to the methyl ester ... 

This route succeeds because reaction occurs farther away from the site of steric hindrance. It is also possible to form the acid chloride of 2,4,6-trimethylbenzoic acid and react it with methanol and pyridine. 

Even the sterically hindered 2,4,6-trimethylbenzoic acid is esterified with methanol under these conditions. Carboxylic acids containing a-halogen atoms are best esterified with DCC without a solvent or base. ... 

The reaction fails when highly sterically hindered substrates are used. From t-butanol and 1-phenylcyclohexane-l-carboxylic acid or 2,4,6-trimethylbenzoic acid, respectively, only the dianhydrides of the carboxylic acids are obtained. Better yields of the thiolesters are obtained by first reacting the carboxylic acid with 1-hydroxybenzotriazole in the presence of DCC, followed by reaction with the thioalcohol. A number of sugar esters are obtained in a similar manner. The use of DCC in the polycondensation of aliphatic dicar-boxylic acids and diols is also reported. These polyester are biodegradable surface active compounds. ... 

The most remarkable property of cyclic polyethers is their ability to form complexes with metal salts, which are soluble in organic solvents. These complexes show enhanced reactivity. Thus sterically hindered esters of 2,4,6-trimethylbenzoic acid which resist saponification by potassium hydroxide in hydroxylic solvents can be hydrolyzed by the... 

Changes in the steric requirements of the benzoic acid component of the ester did suggest a strong influence on the reactivity the reactions of ethylmagnesium bromide with the ethylesters of benzoic acid, o-methylbenzoic acid, and 2,4,6-trimethylbenzoic acid had relative rates of 1000 30 1. An interesting series studied in the same paper consisted of the... 

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