Pyrolysis of quaternary ammonium salts

These reactions are done by injecting reagent together with the acid(s) into the heated inlet of a gas chromatograph, where rapid pyrolysis occurs, and the products 

Initially, tetramethylammonium hydroxide was used [121-124], but tetrabutylammonium hydroxide was better for very voiatile acids [125], and subsequently trimethylanilinium hydroxide (TMAH) was found to be preferable to the tetramethyl compound, and has been widely used as a methylating agent for a variety of different classes of compounds, particularly drugs, but also including acids [120, 126—129]. The w-trifluoro-methyl substituted analogue of TMAH has also been used for free fatty acids and lipid components in biological material, e.g. needle biopsies. This reagent, tri-methyl-(a,a,a-trifluoro-m-tolyl)ammonium hydroxide or TMTFTH, was chosen because it could be used at a 

The acid is dissolved in methanol and titrated with 24% tetramethylammonium hydroxide in methanol to phenol-phthalein. The sample (1-5 /A) is injected for gas chromatography with a flash heater, loosely packed with glass wool, at a temperature of 350 °C [122]. A similar procedure, but with the trimethylammonium salt of the acid made first in a capiUary probe, and the probe then quickly inserted into the heated inlet zone of the gas chromatograph, is claimed to give a higher yield [124], For the volatile formic and for lactic acid, the tetrabutyl-ammonium salts were made instead and pyrolysed in the same way [125]. 

More recently, the reagent of choice for the pyrolytic methylation reactions has been trimethylanilinium hydroxide, because the N,N-dimethylaniline is a better leaving group and thus a lower inlet temperature may be used [126-130]. An even better leaving group is obtained with the m-trifluoromethyl derivative of TMAH, TMTFTH [130]. 

2 Methyl esters with trimethylanilinium hydroxide (TMAH) 

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