Mass spectral studies of a series of N,N-dialkyl aminoethyl-2-chlorides and trimethyl silyl ethers of N,N-dialkyl aminoethane-2-ols under electron impact conditions

Abstract

The electron impact (EI) mass spectra of a series of N,N-dialkyl-aminoethyl-2-chlorides, N(R₁)(R₂)-CH₂-CH₂Cl and trimethylsilyl ethers of N,N-dialkyl aminoethane-2-ols, N(R₁)(R₂)-CH₂-CH₂-O-Si(CH₃)₃, where R₁ and R₂ = methyl, ethyl, propyl and isopropyl, which are precursors of VX type of compounds, are studied. All the compounds (1-20) show abundant molecular ions, in addition to a weak [M - H]⁺ ion, except the N,N-diisopropyl group containing compounds (8 and 18). A general EI fragmentation pattern for the above two series of compounds is discussed. The observed fragment ions are due to simple homolytic cleavages, and they are distinct to allow the identification of the compounds unequivocally including those of isomeric compounds. The primary fragmentation of compounds 120 is β-cleavage, i.e. homolytic cleavage of C-C bond, which is linked to the nitrogen atom. Three types of β-cleavages are possible for these compounds, in which the abundance of β-cleavage product ions is found to depend on the size and structure of the alkyl group attached to nitrogen. The -cleavage fragment ions are found only for N,N-dialkyl aminoethyl-2-chlorides but are absent in the corresponding trimethylsilyl ethers of N,N-dialkyl aminoethane-2-ols. The retention indices are calculated for all the studied compounds (1-20) and are in the ranges of 750.38-1079.24 for 1-10 and 905.23-1190.25 for 11-20.