電子衝撃イオン化質量スペクトルにおける有機ケイ素イオンの単分子分解反応I.1,1,2,2-テトラメチルジシラン, ビス(ジメチルシリル)メタン, 1,2-ビス(ジメチルシリル)エタンイオンのフラグメンテーション(<特集>質量分析法の応用技術)

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The electron impact (EI) mass spectra of three organosilicon compounds with two silicon atoms (CH_3)_2SiH-(CH_2)_n-SiH(CH_3)_2 (n=0〜2) were measured and the fragmentation mechanisms were investigated by the deuterium-labelled technique and the B/E linked-scanning technique. In the EI mass spectrum of 1,1,2,2-tetramethyldisilanes, the main fragmentation produced m/z 73 ions via a four-center transition structure. In bis(dimethylsilyl) methane, methyl radical loss from molecular ion M^+ was the main process, and most of the fragment ions were produced by the secondary decomposition of [M-CH_3]^+. In 1,2-bis(dimethylsilyl) ethane, Si-C bond cleavage occurred simultaneously with the Si-Si bond formation producing m/z 103 ions. In this process, a four-center transition state was involved. The optimized geometries of the neutral molecule and the molecular cation of bis(dimethylsilyl) methane were calculated using the ab initio MO method.
1996-06-05