THEORETICAL STUDY OF INTERACTION BETWEEN DICHLOROCARBENE
R. Hammal1, A. Zeroual1, A. Benharref2, A. El Hajbi1*
1Laboratoire de Chimie Physique, Département de Chimie, Faculté des Sciences, Université Chouaïb Doukkali, BP 20, 24000 El Jadida, Morocco.
2 Laboratoire de Chimie Biomoléculaire, Substances Naturelles et Réactivité, URAC 16, Faculté des Sciences Semlalia, Université Cadi Ayyad, BP 2390, 40000 Marrakech, Morocco.
* Corresponding author. E-mail: firstname.lastname@example.org
Received: 09 April 2013; revised version accepted: 05 June 2013
Investigation of the reaction between dichlorocarbene and a-cis-himachalene using Density Functional Theory (DFT) shows that a stoichiometric reaction produces two dichlorate stereoisomers: (2S,3R)-2,3-dichloro-cis-himachalene and (2R,3S)-2,3-dichloro-cis-himachalene. The first is kinetically preferred. The second is thermodynamically preferred. The stereospecific reaction, which is exothermic, takes place at the a side of the C2-C3 bond. (The a side is that which contains the C1-H of the bond and the ß side is the opposite.) The chemoselectivity of this reaction depends upon the nature of the HOMO and LUMO frontier orbitals of a-cis-himachalene, situated on the double bonds C2-C3 and C7-C13 respectively. The reaction between a-cis-himachalene and an excess of dichlorocarbene under the same conditions is also exothermic and produces two tetrachlorate stereoisomers: (2S,3R,7R)-[2,3:7,13]-tetrachloro-cis-himachalane and (2S,3R,7S)-[2,3:7,13]-tetrachloro-cis-himachalane, the first of which is both thermodynamically and kinetically preferred. Interatomic distances, bond angles and dihedral angles of the reaction products were calculated.
Keywords: a-cis-himachalene; DFT (Density Functional Theory); Chemoselectivity; Stereoselectivity; Dichlorocarbene; Thermodynamics; Interatomic distance; Bond angle.