Isotope effects and H/D scrambling in the fragmentation of labelled propenes

The fragmentation reaction [C 3 (H,D) 6 ] + · → [C 3 (H,D) 5 ] + + (H, D) has been examined in the metastable decomposition region for two pairs of labelled propenes: CH 3 CDCH 2 ,CD 3 CHCD 2 and CD 3 CHCH 2 , CH 3 CDCD 2 . The results indicate that complete hydrogen scrambling occurs in the propene molecular ion prior to fragmentation. The isotope effect kH/kD is in the range 2·1 to 3·3.