Density Functional Studies of Halonium Ions of Ethylene and Cyclopentene

Abstract

. sigalas@chem.auth.gr A computational study of a variety of C 2 H 4 X + , C 5 H 8 X + , C 5 H 8-n (OH) n X + (n=1, 2), where X= Cl and Br, has been carried out. The potential energy surfaces of all molecules under investigation have been scanned and the equilibrium geometries and their harmonic vibrational frequencies have been calculated at the Becke3LYP/6-311++G(d,p) level of theory. The bonding in bridged halonium ions is discussed in terms of donor -acceptor interaction between ethylene and halogen orbitals in the parent ethylenehalonium ion. The relative energies, the equilibrium geometries and the proton and carbon NMR chemical shifts calculated are in good agreement with existing experimental and theoretical data.