Inorganic Chemistry, Vol.48, No.23, 11434-11443, 2009
Density Functional Theory Study of the Mechanisms of Oxidation of Ethylene by Chromyl Chloride
The mechanistic pathways for the formation of epoxide, 1,2-dichloroethane, 1,2-chlorohydrin, acetaldehyde, and vinyl alcohol precursors in the oxidation of ethylene by chromyl chloride has been studied using hybrid density functional theory at the B3LYP/LACVP* level of theory, The formation of the epoxide precursor (Cl-2(O)Cr-OC2H4) was found to take place via initial [2 + 2] addition of ethylene across the Cr=O bonds of CrO2Cl2 to form a chromaoxetane intermediate. The pathway involving initial [3 + 2] addition of ethylene to the oxygen and chlorine atoms of CrO2Cl2, which has not been explored in earlier studies, was found to be favored over [3 + 2] addition of olefin to two oxygen atoms of CrO2Cl2, The formation of the 1,2-dichloroethane precursor, which was found to take place via [3 + 2] addition of ethylene to two chlorine atoms of CrO2Cl2, is slightly favored over the formation of the epoxide precursor. The 1,2-chlorohydrin precursor has been found to originate from [3 + 2] addition of ethylene to the oxygen and chlorine atoms of CrO2Cl2 as opposed to [2 + 2] addition of ethylene to the Cr-Cl bond. The vinyl alcohol precursor O=CrCl2-(OH)CH=CH2 has been found to exist only on the triplet potential energy surface. The acetaldehyde precursor (O=CrCl2-OCHCH3) was found to be the most stable species on the reaction surface. Hydrolysis may be required to generate the epoxide, 1,2-dichloroethane and 1,2-chlorohydrin from the respective precursors.