二甲基(五氟苯基)硅烷衍生物的质谱重排反应

Electron-impact-induced rearrangements in the dimethyl (pentafluorophenyl) silyl derivatives

利用气相色谱质谱联用仪在电子轰击离子源下对20个二甲基(五氟苯基)硅烷衍生物进行分析,发现大部分化合物质谱图上无分子离子峰,少数化合物可观察到较弱的分子离子峰。所有化合物质谱图上都具有较强的[M-CH3]+离子,且在个别化合物的谱图上表现为基峰,该离子来自游离基中心诱导发生的α(C-Si键断裂)裂解。各化合物的谱图上均具有m/z 77和m/z 79的特征离子,在绝大多数化合物的谱图上表现为基峰。对离子进行归属时发现该类离子并不能通过化合物分子内键的直接裂解而得到,推测该类离子是通过进行分子内的骨架重排反应而得到的三配位硅正离子,推断其生成途径为单分子亲核取代反应历程(SN1)。进一步对不含氟的二甲基(苯基)硅烷衍生物进行分析,未检出该类重排特征离子,从而印证了对于二甲基(五氟苯基)硅烷衍生物中重排离子生成途径的推测。

The mass spectra of some dimethyl （pentafluorophenyl） structural information and revealed that these compounds are quite They exhibited weak molecular and strong [ M-CH3 ] ^＋ ions, characteristic for the CH3-Si bond cleavage of the some compounds. Numerous rearrangement ions silyl derivatives provided valuable stable to electron-impact-induced. and fragment ions, which are molecules. It- the base peak in the mass spectra of were detected, however, the most prominent one involves the migration of a fluorine atom to the silylium ions, leading to the base peak （ m/z 77, m/z 79） in the mass spectra of fluorodimethylsilane ion and fluoro （methyl） silanol ion. The mechanism of these fragmentations was studied with the GCMS analysis and deuterium labeled analogs were reported.