Conservation of spin angular momentum in proton transfer to C−(4S)

The rate constants for the proton-transfer reactions of C−(4S) with HCl, HCN, H2S, SiH4, and CH3COCH3 have been measured at 296±2°K with the flowing afterglow technique. The reactions with CH3COCH3 and SiH4 which must involve a spin-forbidden proton transfer, were observed to proceed at low probabilities which can be accounted for by the violation of the Wigner–Witmer spin conservation rule. The probability of proton transfer is observed to be enhanced considerably (×10) for the more exothermic reactions with H2S, HCN, and HCl in which the spin-allowed production of the low-lying excited CH(4Σ) state is energetically accessible.