Cycloorganosilyl Derivatives for the Determination of Alcohols and Carboxylic Acids by Gas Chromatography/Mass Spectrometry

Abstract

New silylating agents—methyl(trimethylene-, tetramethylene-, pentamethylene)silyl chlorides, ethyl(tetramethylene-, pentamethylene)silyl chlorides and chloromethyl(pentamethylene)silyl chlorides—are suggested for the investigation of alcohols and carboxylic acids by gas chromatography/mass spectrometry (GC/MS). It is shown that corresponding derivatives may easily be prepared by solution reactions and by on-column silylation. All the derivatives appeared to be less mobile in GC than trimethylsilyl derivatives. Under electron impact (EI), all the derivatives [except chloromethyl(pentamethylene)silyl derivatives] of primary alcohols form pronounced molecular ions. For all kinds of derivatives obtained from secondary alcohols, the most characteristic fragmentation is due to cleavage of a C–C bond near to the silyloxy group. The mass spectra of trimethylene- and tetramethylenesilyl ethers derived from isomeric straight-chain and branched alcohols differ quantitatively. Main fragmentation reactions of the latter derivatives under EI conditions are elucidated with the aid of D-analogues. The mass spectra of cycloorganosilyl esters of alkanoic acids are less characteristic and are due mainly to the loss of an alkyl radical from the silicon atom or to a cleavage of the silacycloalkane ring in molecular ions.