A new potential toxaphene congener: synthesis, GC/EI-MS study, crystal structure, NMR analysis, and ab initio calculations of 3-endo,5-endo-dichloro-7,7-bis-chloromethyl-4-dichloromethyl-tricyclo[2.2.1.0(2,6)]heptane

A new potential toxaphene congener 3-endo,5-endo-dichloro-7,7-bis-chloromet hyl-4-dichloromethyl-tricyclo [2.2.1.0(2,6)]heptane 2 has been isolated fro m reaction mixture obtained by the chlorination of 2-exo,10,10-trichlorobor nane 1. The X-ray structural analysis of 2 revealed an unusual tricyclic st ructure, where the two chlorine atoms occupying endo-positions are in close spatial proximity with each other and near to the neighbouring CHCl2 group . Further, it revealed that the symmetry of the molecule is distorted. The H-1 and C-13 NMR spectra of 2 have been assigned by means of H-1, H-1 doubl e-quantum filtered correlation spectroscopy (DQF COSY), PFG H-1, C-13 HMQC (pulsed field gradient heteronuclear multiple-quantum coherence), H-1, C-13 heteronuclear multiple bond correlation (HMBC) experiments, and computer a ided H-1 NMR spectral analysis. The asymmetry of 2 is also discernible on t he H-1 NMR parameters. In addition, gas chromatographic (GC) properties and electron impact (EI) mass spectrum of 2 has been studied. Ab initio Hartre e-Fock (HF) method with the basis set 6-31G(d) has been used for the optimi zation of the equilibrium geometry and calculation of total energy for 2. T he optimized geometry is in good agreement with the crystal structure. Acco rding to the rotation energy profile calculated at the HF/6-31G(d) level, r otation of the chloromethyl and dichloromethyl groups are highly unlikely a t the room temperature. (C) 2001 Elsevier Science Ltd. All rights reserved.