Acta Chimica Sinica ›› 1982, Vol. 40 ›› Issue (12): 1094-1102.
JIE CAO-XIAN, LIU RUO-ZHUANG
Ab imritio MO calculation has been performed in an effort to determine the possible reaction path of the addition reaction of HF on C2H4.Two limiting reaction mechanisms have been considered.One is a molecular addition which proceeds stereo-specifically via a cyclic four-center transition state and exclusively occurs with cis stereoohemistry.The other is a molecular addition which proceeds via a transition state in which the HF molecule is normal to the plane of ethylene and above the C=C bond midpoint.From the results of calculation it is found that the firat mechanism is the possible reaction path.The calculated activation energy is 58.68 kcal/mol (246.32 kJ/mol), which is to be compared to the experimental value 54±3 kcal/mol.The charge transfer between HF and C2H4 in the complex has been discussed in terms of Mulliken's population.It was found that negative charge (electrons) is transferred from C3H4 to HF when the intermolecular distance R is much greater or much smaller than R0 (the intermolecular distance in the transition state).But when R is near R0, we found that tho direction of charge transfer is reversed.This phenomenon is explained from a frontier orbital point of view.Furthermore, it was shown that Woodward-Hoffmann rules do not fit to the present case because the fluorine atom brings more than one orbitals into play during the reaction process.
JIE CAO-XIAN, LIU RUO-ZHUANG. AN AB INITIO MO STUDY ON ADDITION REACTION OF HF ON ETHYLENE[J]. Acta Chimica Sinica, 1982, 40(12): 1094-1102.
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