GEMINAL SUBSTITUENTS EFFECTS .1. THERMOCHEMISTRY OF 1-NITROADAMANTANE, 2-NITROADAMANTANE, 2,2-DINITROADAMANTANE AND 2-CYANO-2-NITROADAMANTANE

The heats of combustion of 1-nitroadamantane (1), 2-nitroadamantane (2), 2,2-di-nitroadamantane (3) and 2-cyano-2-nitroadamantane (4) were measured by combustion calorimetry, and the heats of sublimation were derived from the temperature dependence of the vapour pressure measured in a flow system. The results for ΔHXXXc(c) and ΔHSub (in kJ mol-1, standard deviation in parentheses) are: 1, -5824.1 (±2.2) and 63.6 (±1.0); 2, -5841.0 (±2.2) and 58.0 (±2.3); 3, -5685.2 (±1.0) and 96.4 (±1.4); 4, -6238.4 (±1.5) and 70.0 (±1.9). A comparison of the resulting heats of formation ΔHXXXf(g) (in kJ mol-1, standard deviation in parentheses) for 1 = -191.1 (± 2.4), 2 = -179.8 (±3.2), 3 = -154.3 (±1.7) and 4 = -21.0 (±2.5) reveals a destabilizing interaction of the geminal substituents in 3 and 4 amounting to 59 kJ mol-1 (nitro/nitro) and 33 kJ mol-1 (nitro/cyano) respectively. © 1990.