Role of tunneling of hydrogen in the Norrish type II processes in a thione and a ketone

Intra-molecular hydrogen abstraction reactions were examined in pentane-2-thione in its lowest triplet state using the AM-1 semiempirical molecular orbital method with the geometry optimisation in the unrestricted Hartree-Fock frame. Results were compared with those of pentane-2-one. The role of tunneling of hydrogen was examined in both the conventional transition-state approach and in the RRKM theory of unimolecular reactions. Results reveal that tunneling of hydrogen is less significant to sulfur than to oxygen