The Generation of the Thiocyanate Radical and Cation from the Thiocyanate Anion [SCN]- in the Gas Phase. The Rearrangements of Neutral and Cationic SCN. A Joint Experimental and Theoretical Study

Abstract

A comparison of the neutralization reionization and charge reversal mass spectra of the thiocyanate anion (SCN)- show that, while the majority of SCN radicals and cations formed by these processes retain their connectivity, a minority of both radicals and cations are energized and rearrange to isomers that dissociate by loss of C. Theoretical calculations at the CCSD(T)aug-cc-pVDZ//B3LYP/6-31+G(d) level indicate that the thiofulminate species (SNC) is the likely rearranged product in each case. Doublet neutral SCN rearranges through cyclic SCN to the thiofulminate radical SNC in a reaction endothermic by 29.9 kcal mol-1 and requiring neutral SCN to have an excess energy of ≥48.5 kcal mol-1; a result in agreement with a previous theoretical study of SCN. Triplet (ground state) (SCN)+ may rearrange to triplet (SNC)+ in a concerted reaction endothermic by 20.6 kcal mol-1 and with a barrier of 45.1 kcal mol-1. Singlet (SCN)+, in contrast, rearranges to singlet (SNC)+ through a cyclic SCN intermediate in a stepwise process endothermic by 18.2 kcal mol-1, with a maximum barrier of 39.5 kcal mol-1.