STRAINED UNSATURATED MOLECULES - THEORETICAL-STUDY OF ACYCLIC AND CYCLIC CUMULENES AND ACETYLENES

There is a high probability for the photochemical formation of highly strained isomers of benzene, hydrocarbons 31-34, at very low temperatu res in inert matrices. This is also true for various derivatives and a nalogues of o-benzyne (22), benzologues of three isomers of benzyne (5 2-54), and six-membered cycles having two or three triple CC bonds in the ring (25-27). These systems as well as the radical ions of o-benzy ne and cyclic C(n) systems (46-51) have been studied theoretically. Th e stability and structure estimates were based on non-empirical and se mi-empirical quantum chemical calculations. The reliability of these c alculations has been partly tested by comparing the calculated and obs erved heats of formation for a representative ensemble of unsaturated and strained hydrocarbons. Some of the C(n) systems (acyclic and cycli c) can, in principle, exist in two forms which differ in their electro n distribution and therefore also in their structure.