Self consistent field molecular orbital studies on chlorinated cumulenes

Abstract

Cumulenes are compounds containing a unit of 'n' carbon atoms with (n-1) double bonds between them (n&gt;3). The members are propadiene(allene), butatriene, pentatetraene etc. A systematic study of chlorination on cumulenes is done in the present study. Geometrical optimisation is carried out on the cumulenes using RHF wave functions with 31-G basis set using Gaussian -94. Semi-empirical calculations(CNDO/2) are performed to elicit the trend of chlorination. Chlorination of cumulenes brings out some interesting properties such as lowering of energy, redistribution of charge density, stability of odd number of double-bonded cumulenes, etc. The ionisation potential of odd number of double bonded cumulenes are high compared to that of even number of double bonded cumulenes. To study the trend of redistribution of charge densities due to chlorination it is sufficient to substitute a single chlorine atom. The inner carbon atoms distribute their electronic charges in the direction of chlorinated carbon atoms. Chlorination leads to an increased <i>p_z </i>orbital occupation of inner carbon atoms. Using finite perturbation technique, proton coupling constants of butatriene are also calculated.