Tetramethylammonium carboxylates

A. Joll, T. Huynh and A. Heitz, Off line tetramethylammonium hydroxide thermochemolysis of model compound aliphatic and aromatic carboxylic acids decarboxylation of some ortho and/ or para substituted aromatic carboxylic acids, J. Anal. Appl. Pyrol., 70, 151 167 (2003). 

Characteristic markers of Venice turpentine are larixol and larixyl acetate, but in many cases they may remain undetected, as larixyl acetate hydrolyses and the methylation of hydroxyl groups is not as effective as for carboxylic acids. On-line derivatization with tetramethylammonium hydroxide (TMAH) is, for instance, scarcely effective on hydroxyl groups and involves a number of secondary reactions (isomerization, dehydration and cleavage of hydrolysable bonds) due to the strong alkalinity of the TMAH solution. When the experimental conditions are such that THM of labdanes occurs larixol and larixyl acetate are detected as a single peak since in the derivatization process larixyl acetate is hydrolysed to larixol [29]. 

Newkome et al. were the first to synthesise symmetrical, quater-directionaF cascade molecules with a carbon scaffold bearing 36 terminal carboxyl groups -all at an equal distance from the neopentyl core (Fig. 6.20a). The carboxyls were converted into the corresponding ammonium and tetramethylammonium car-boxylates. Synthesis of these dendritic unimolecular micelles with hydrophobic core and hydrophilic shell was accomplished up to the fourth generation by coupling of a dendritic hypercore (constructed from 4,4-bis(4 -hydroxyphenyl)-pentanol monomer) and PEG mesylate (PEG = polyethylene glycol). Dyes such... 

Analytical pyrolysis with field ionization mass spectrometry (online Py-FIMS) or in combination with GC/MS (Curie point Py-GC/MS) led to a significant increased number of identified subunits (e.g., Bracewell et al., 1989 Schulten et al., 2002). In addition, the application of tetramethylammonium hydroxide (TMAH) methylation, followed by GC/MS, was successfully applied. The most abundant pyrolysis products identified are benzene, phenol and furan derivatives, aliphatic and carboxylic compounds, and indene derivatives (Schulten et al.,2002). New approaches have been used for the quantification of n-alkyl fatty acids of DOM and isolated fractions in the form of individual compounds after solvent extraction followed by derivatiza-tion with TMAH. 

After LLE of phenols and carboxylic acids in water, on-line methylation with 51 was applied together with large volume injection (100 xL). The solvent was removed before the analytes were transferred into the GC column with MS detection in full scan mode. Volatile fatty acids, dicarboxylic acids, benzoic acids and phenols in water, at concentrations of 0.4 to 0.1 p.M, could be determined in 5 mL samples. Lactic, pyruvic and malonic acids required higher concentrations due to their higher water solubility and lower methylation rates" . Samples of particulate matter were subjected to LLE with THE, and hydrolysis/methylation of the extract with tetramethylammonium hydroxide. 

Methyl esters are the most commonly used derivatives of the carboxylic groups. There are several methods for the preparation of methyl esters diazomethane, methanolic solution of boron trifluoride, pyrolysis of tetramethylammonium salts, methylation with 2,2-dimethoxypropane, etc. 

Grasset, L., Guignard, C., and Ambles, A., Free and esterified aliphatic carboxylic acids in humin and humic acids from a peat sample as revealed by pyrolysis with tetramethylammonium hydroxide or tetraethylammonium acetate, Org. Geochem., 33, 181-188, 2002. 

The last step calls for the development of the HOL polymer/photoresist film stack in an aqueous basic solvent such as 0.26 N tetramethylammonium hydroxide. This will dissolve and wash away the exposed part of the resist, comprising the carboxylic acid moieties. The preferential diffusion of the HOL into the exposed area of the photoresist results in deprotection of the photoresist polymer at the edge of the unexposed features, leading to their dissolution. This is the basis of the CD reduction, improved process window, and exposure latitude, and smoother sidewall and line edge profile of photoresist features processed with HOL relative to the features processed without HOL. ... 

Wood and co-workers have reported an extensive series of careful measurements from 0.1 to 0.8 mol kg on alkali halides, nitrates and carboxylates, and on tetramethylammonium halides. An equilibrium technique was used. The results were fitted to extended Debye-Huckel equations. The solvent has a high dielectric constant (178 at 30.5°C) and osmotic and activity coefficients are higher at corresponding concentrations than in water. The sequences of specific differences are, however, the same as in water. This implies that the... 

Carboxylic acid methyl esters. A methanolic soln. of oleanolic acid containing phenolphthalein as indicator titrated with a soln. of tetramethylammonium hydroxide in the same solvent, which is then removed by distillation, and the residual tetramethylammonium salt heated under reduced pressure with distillation of the resulting trimethylamine -> methyl oleanolate. Y 83%. F. e. s. V. Prelog and M. Piantanida, H. 244, 56 (1936) by gas-diromatography s. A. S. Hyman, J. Chromatogr. 45, 132 (1969) ethers from quaternary ammonium hydroxides and acetates cf. J. MacGee and K. G. Allen, Steroids 16, 19 (1970). 

Derivatization of acids with 2-nitrophenylhydrazine has been described in a number of publications [111-115]. N,N -Dicyclohexylcarbodiimide (DCCI) [111] or 1-ethyl-3-(dimethylaminopropyl)carbodiimide (EDCi) (114,115) was used for the activation of the carboxylic acid function. Normally the derivatives were detected at 550 nm. Miwa and Yamamoto [115] applied this method to the determination of urinary dicarboxylic acids, which reacted with 2-nitrophenylhydrazine to form monohydrazides. The adds were extracted from acidified urine with ethyl acetate and dried. After derivatization, the monohydrazides of the dicarboxylic acids were first separated from the hydrazides of monocarboxylic acids and other interfering substances by a two-step extraction. The recoveries varied from 27.6-103.1%, depending on the polarity and the water solubility of the acids. The separation of monohydrazides of 11 straight- and branched-chain dicarboxylic acids was performed on an ODS column at 40 °C by isocratic elution with acetonitrile-phosphate buffer containing counter-ions such as tetramethylammonium as mobile phase. Detection was at 400 nm. 

Tetramethylammonium hydroxide (TMAH) is the most commonly used reagent for THM, and TMAH thermochemolysis has been extensively applied to the characterization of organic natural materials [98,103,104,107,108,124,127,134-138]. Py with TMAH involves the deprotonation of carboxylic acids and the hydrolysis of ester and ether bonds, followed by the formation of tetramethylammonium salts, which are subsequently subjected to thermal dissociation and leads to the formation of the corresponding methyl derivatives. 

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