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

The mechanisms for the insertion of alkylidenecarbenes into O-H bond of water have been investigated with B3LYP/6-311G(d,p) method. The XYC=C + H2O (XYC-C: H2C=C, HFC=C, HCIC=C, HBrC=C, H(CH3)C=C, F2C=C, Cl2C=C, Br2C=C, (CH3)(2)C=C) 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: HFC=C > HClC=C > HBrC=C > H(CH3)C=C > H2C=C. The same phenomenon can be found in double substituted alkylidenecarbene, that is, F2C=C > Cl2C=C > Br2C=C > (CH3)(2)C=C > H2C=C. Our theoretical findings suggest that the singlet-triplet splitting (Delta E-ST) of the XYC=C species can be used as a guide to predict its activity for insertion reactions. (c) 2007 Published by Elsevier B.V.