ab initio study of the size dependence of the melting point for cycloalkanes “CnH2n”

Abstract

Cycloalkanes “C_nH_2n” composed of hydrocarbon and having one or more rings of carbon atoms in their structure are typical organic cyclic compounds. The physical properties of cycloalkane are similar to those of alkane, but the melting point (m.p.) of cycloalkane having one ring, representative physical property, is found to strongly on the number of carbon atoms; the m.p. increases as the cycloalkane-size increases and has local minima at n = 5, 7, 9, 11 and 13. According to our latest study, semi-empirical MO calculation was used to calculate the stable structure of cycloalkane, it was revealed to relate strongly the m.p. of cycloalkanes with their molecular symmetry. In the present study, the size dependence of the m.p. of cycloalkanes was discussed in terms of comparison with the specific heat obtained from ab initio calculation. We found that the size dependence of the m.p. of cycloalkanes was caused by their structures mainly and by their specific heat slightly.