Calculations on substituted cyclopropenones and diphenylcyclopropenethione

Comparative CNDO/2 molecular orbital calculations are reported for cyclopropenone, dialkylcydopropenones, diphenylcyclopropenone and diphenylcyclopropenethione. The results are compared with ab initio calculations and with experimental studies. The effects of varying the alkyl groups (R = methyl, ethyl, n-propyl and n-butyl) are slight. The alkyl groups increase the absolute charge on the oxygen, decrease the absolute charges on the ring carbons and increase conjugation. In the diphenyl compounds, the oxygen and sulphur atoms are extremely negatively charged.