Substituent effects of the groups CH2M(CH3)3(M = C to Pb) and M(CH3)3(M = Si to Pb) from proton and carbon-13 chemical shift measurements on 4-substituted styrenes

Proton and carbon-13 chemical shifts for 4-substituted styrenes are used to estimate σI and σR° for M(CH3)3 and CH2M(CH3)3 derivatives (M = Si, Ge, Sn, or Pb). The derived constants are consistent with previous conclusions concerning electronic effects of these groups and indicate that σ–π hyperconjugation is an important mechanism for their transmission.