C.V. Viswanathan

Two-dimensional reaction thin-layer chromatography in the analysis of phosphatide plasmalogens.

Abstract A two-dimensional reaction thin-layer chromatography procedure on micro- samples of mixtures of alkenyl acyl and diacyl phosphatides has been described by which it is possible to determine simultaneously their plasmalogen content, the fatty acid composition of invidual analogs and the fatty aldehyde composition of the alkenyl acyl analog.

Mass spectrometry of long-chain aliphatic aldehydes, dimethyl acetals and Alk-1-enyl ethers

Mass spectra of long-chain saturated and unsaturated aliphatic aldehydes, dimethyl acetals and alk-1-enyl methyl ethers are reported and discussed. Using deuterium labeled aldehydes, knowledge about the mass spectral fragmentation is obtained. The m/e M-44 ion is formed by a rearrangement different from the mechanism postulated previously for short-chain aldehydes. A series of hydrocarbon fragments with even mass numbers of 68+14n (n=0,1,2...) appear in the spectra of all three series of compounds.

Thin-layer chromatography of homologues and vinylogues of higher fatty aldehydes, dimethyl acetals, and 2,4-dinitrophenylhydrazones

A method is described for the separation of fatty aldehydes, aldehyde dimethyl acetals and methyl esters of fatty acids into classes by two-dimensional thin-layer chromatography. Separations of individual members of long-chain even-numbered saturated fatty aldehydes, their dimethyl acetals and 2,4-dinitrophenylhydrazones and the C18 unsaturated aldehydes (oleyl, linoleyl, and linolenyl) and their corresponding derivatives were achieved by reversed-phase partition thin-layer chromatography. The critical pairs having identical RF values in the reversed-phase system were separated by adsorption chromatography using silver nitrate-impregnated Silica Gel G plates. With this technique the cis-trans isomers also could be separated as shown by 2,4-dinitrophenylhydrazine derivatives.

Interconversion of fatty aldehydes and dimethyl acetals at low temperatures.

Facile procedures are described for nearly quantitative conversion of saturated and unsaturated fatty aldehydes to their dimethyl acetals, and vice versa, at low temperatures. The methods are based on the chemical behavior of aldehydes and dimethyl acetals in 100% sulfuric acid. Under the experimental conditions described, no side reactions seemed to occur. The purity of the aldehydes and dimethyl acetals was ascertained by thin-layer chromatography, infrared spectra and other techniques.

Two-dimensional reaction thin-layer chromatography in the analysis of mixtures of alkenyl acyl-, alkyl acyl- and diacyl choline phosphatides

Abstract Micro-samples of mixtures of alkenyl acyl-, alkyl acyl- and diacyl choline phosphatides, after their conversion into three families of diglyceride acetates by subjecting them to phospholipase C action followed by acetylation, were analyzed by a two-dimensional reaction thin-layer chromatographic procedure which permitted a quantitative determination of the three analogs, their individual fatty acids compositions and fatty aldehyde composition of the alkenyl acyl analog.

Isolation and characterization of alk-1-enyl alkyl ethers

Abstract Several alk-1-enyl alkyl ethers were obtained during preparative gas chromatography of acetals derived from saturated and unsaturated fatty aldehydes and methyl, ethyl, propyl and butyl alcohols. Analysis of these substituted vinyl ethers by argentation chromatography, gas-liquid chromatography, infrared spectroscopy, nuclear magnetic resonance spectroscopy and mass spectrometry showed that they were a mixture of cis and trans isomers. Aluminum metal was found to catalyze the decomposition of the acetals to the corresponding alk-1-enyl alkyl ethers. The cis-trans percentage composition was influenced by column characteristics, as well as by the alcohol moieties of the acetals, but the aldehyde moieties of the acetals had no influence.

A simple method of preparing alcohol acetates, wax esters, and cholesterol esters

T HE EXCESS OF L I T H I U M A L U M I N U M HYDRIDE, used in the reduction of carboxylic esters to the corresponding alcohols, is decomposed either by water or ethyl acetate (1). Our experience in using ethyl acetate in these reactions indicated .partial acetylation of the alcohols, probably because of in-situ formation of lithium aluminum ethylate. This assumption seemed to be confirmed when palmityl alcohol could be quantitatively acetylated with ethyl acetate in the presence of a similar basic catalyst, sodium methylate. In the present communication the method of preparing alcohol acetates, wax esters, and cholesterol esters in high yields is described. Five grams of oleyl alcohol were dissolved in 50 ml of ethyl acetate and mixed with 100 mg of sodium methylate. The mixture was agitated vigorously with a magnetic stirrer in a 250-ml flask. The flask was flushed with nitrogen, immersed in a water bath maintained at 70C, and evacuated with a water aspirator at a rate such that the excess of ethyl acetate and ethyl alcohol resulting from the reaction were completely removed in 15 min. The flask was cooled, and the residue was extracted with diethyl ether; the extract was washed free of alkali with wa te r and dried over anhydrous sodium sulfate. The oleyl acetate so obtained was purified by thin-layer chromatography (TLC) (system: silica gel G / toluene) before infrared analysis and a melting-point determination (rap, 17C to 1 6 C ) . The reaction between 1.2 g of methyl linolenate and 1.0 g of palmityl alcohol in the presence of 100 mg of sodium methylate (in the absence of any solvent) was carried out as described in the case of oleyl acetate except that the reaction was continued for 1 hr. Palmityl linolenate was purified by TLC before infrared analysis, and the melting point was determined after crystallization from ethanol (mp, 11.5C to 12.5C). The reaction between 100 mg of cholesterol, purified by the dibromide method, and 70 mg of methyl palmitoleate in the presence of 20 mg of sodium methylate in 15 ml of benzene was conducted in the same manner as de-

A new aldehydogenic phospholipid—an artifact

Abstract The storing of phosphatide plasmalogens in a solution of chloroform-methanol resulted in the formation of an artifact which was easily detectable by thin-layer chromatography after reduction with lithium aluminum hydride. The reduction product reacted positively to phenylhydrazine-sulfuric acid reagent. This property together with its chromatographic behavior on thin layers of Silica Gel G suggested the artifact as an addition product of plasmalogens and methanol. The structure of the compound (artifact) was determined by infrared and nuclear magnetic resonance spectroscopy as well as by mass spectrometry. The possible biological significance of such an addition reaction is discussed.