Communication: Infrared spectroscopy of protonated allyl-trimethylsilane: Evidence for the β-silyl effect

Abstract

β-trimethylsilyl-2-propyl cation has been formed by the gas phase protonation of allyl-trimethylsilane and characterized by infrared multiple photon dissociation spectroscopy. The experimental Cβ-Cα+ stretching feature at 1586 cm−1, remarkably blue-shifted with respect to a C−C single bond stretching mode, is indicative of high double bond character, a signature of β-stabilizing effect due to hyperconjugation of the trimethylsilyl group in the β-position with respect to the positively charged carbon. Density functional theory calculations at the B3LYP/6-311++G(2df,2p) level yield the optimized geometries and IR spectra for candidate isomeric cations and for neutral and charged reference species.

Trimethylsilyl Compounds for the Interfacial Stabilization of Thiophosphate‐Based Solid Electrolytes in All‐Solid‐State Batteries

“…600 and 820 cm −1 , which are assigned to Si-CH 3 vibration, in their Raman and IR spectra, respectively. [49,50] For TMS-SH and TMS-OH, the supernatant solutions retrieved after the centrifuge, denoted as after adsorption in Figure 1, showed significant decreases in intensity of these peaks compared to the pristine solutions. This reveals that the concentrations of TMS-SH and TMS-OH in the retrieved solutions decreased compared to the pristine solutions because significant amounts of TMS-SH and TMS-OH were adsorbed on the LPSCl surface.…”

Esterifications with 2-(Trimethylsilyl)ethyl 2,2,2-Trichloroacetimidate

“…Proton transfer from the acid 5 to the imidate 2 forms the protonated imidate 20, which then dissociates trichloroacetamide 4 leading to the formation of the β-silyl carbocation 21. β-Silyl carbocations like 21 are known to be unusually stable due to hyperconjugation from the nearby silicon-carbon bond [43]. Based on experimental and computational evidence, the structure of this cation is best represented by the bridged silyl cation 22 rather than the primary carbocation structure represented by 21 [43,44]. Addition of the carboxylate to the cation 22 then provides the observed ester product.…”

Direct Spectroscopic Evidence of Hyperconjugation Unveils the Conformational Landscape of Hydrazides

“…This phenomenon may be a useful spectroscopic tool for conformational assignment purposes in more complex hydrazides. It may be also pointed out that the vibrational signature of hyperconjugation is rarely used for conformational analysis,23, 24 despite the ubiquity of hyperconjugation25, 26 and the high added‐value of such a characterization. Besides hydrazides,19 large hyperconjugation‐induced red‐shifts can be anticipated in biologically relevant molecules, as suspected from free NH stretch calculations on a tetrahydroisoquinoline derivative 27.…”