HEATS OF COMBUSTION AND STRAIN ENERGIES OF SOME CYCLOPHANES

Heats of combustion and vapor pressure curves have been determined for 2,2-metacyclophane (II), 3,3-paracyclophane (III), 2,2-metaparacyclophane (IV), 1,8-paracyclophane (V), 6,6-paracyclophane (VI), 2,2-perhydroparacyclophane (VII), From these data, values have been derived for the heats of combustion and formation of both the solid and gaseous compounds. Heats of crystal transition, and of fusion, have been measured for II, III, and IV. Measurements have also been made of the heat capacities of 2,2-paracyclphane, II, III, and IV at 300°K and 318°K. Experimental strain energies at 298°K and in a motionless state are derived from the heats of formation by comparisons with group contributions and also by comparison of heats of strain relieving reactions with reference reactions. The crystal and gaseous heats of formation and experimental room temperature strain energies are respectively (in kcal mole-1: II, 18·7 ± 1·5, 40·7 ± 1·9, 12; III 6·24 ± 0·63, 30·92 ± 0·88, 12; IV, 31·26 ± 0·51, 52·18 ± 0·73, 24; V, -19·6 ± 1·7, 6·9 ± 2·2, 2; VI, -46·0 ± 2·3, -18·5 ± 2·8, -7; VII, -58·4 ± 3·1, -37·4 ± 3·6, 26. The structure, strain energy and thermodynamic functions of VII have been calculated by energy minimization using a set of transferable potential functions. © 1969.