33335-67-0Relevant academic research and scientific papers
Rearrangement of nascent α-silyl-substituted carbenium ions in the gas phase. 1,2-hydrogen versus 1,2-methyl versus 1,2-phehyl migration
Bakhtiar,Holznagel,Jacobson
, p. 3227 - 3235 (2007/10/02)
The unimolecular rearrangement of incipient α-silyl-substituted carbenium ions ((CH3)2HSi-+CH2 (5), (CH3)3Si-+CH2 (6), (CH3)3Si-+CHCH3 (7), (C6H5)(CH3)HSi-+CH2 (8)) in the gas phase has been studied by using Fourier transform mass spectrometry (FTMS). Incipient α-silyl-substituted carbenium ions were formed by chloride elimination from the corresponding α-chloroalkylsilanes. These nascent carbenium ions rearrange to the corresponding silylenium ions by direct 1,2-group migration (H, CH3, C6H5) from silicon to carbon. The structures of the resulting silylenium ions were determined by specific ion/molecule reactions with methanol and isotopically labeled ethene. The driving force for this rearrangement (1,2-group migration) is the increased thermodynamic stability of the silylenium ion. 5 undergoes exclusive 1,2-hydrogen migration, whereas 6 yields specific 1,2-methyl migration. 7 undergoes rearrangement by both 1,2-methyl and 1,2-hydrogen migration. For 7,1,2-hydrogen migration involves the transfer of a hydrogen atom from the methyl group bound to the carbenium center yielding (CH3)3Si(CH2CH2)+. The incipient carbenium ion, 8, yields competitive 1,2-phenyl (0.94) and 1,2-hydrogen (0.06) migration with no methyl migration observed. These results suggest the following relative migratory aptitude: phenyl > hydrogen ? methyl.
