Insertion of singlet alkylidenecarbenes into O-H bond of water: A theoretical prediction

The mechanisms for the insertion of alkylidenecarbenes into OH bond of water have been investigated with B3LYP/6-311G(d,p) method. The XYCC + H2O (XYCC: H2CC, HFCC, HClCC, HBrCC, H(CH3)CC, F2CC, Cl2CC, Br2CC, (CH3)2CC) system is the subject of the present study. According to our model calculations these insertion reactions can yield vinyl alcohol products and for a given single substituted alkylidenecarbene will yield cis-trans-isomer mixtures. Moreover the reactivity of alkylidenecarbene decreases in the order: HFCC > HClCC > HBrCC > H(CH3)CC > H2CC. The same phenomenon can be found in double substituted alkylidenecarbene, that is, F2CC > Cl2CC > Br2CC > (CH3)2CC > H2CC. Our theoretical findings suggest that the singlet-triplet splitting (ΔEST) of the XYCC species can be used as a guide to predict its activity for insertion reactions.