The MINDO/3, MNDO and AM1 methods were used to calculate systematically the heats of formation for 32 nitric acid esters at their optimized mol. geometries. Compared to experimental values, the MNDO calculated results are much larger, and the MINDO/3 calculated results compare better the observed data in condensed phase. By correcting for the repulsive van der Waals energy among atoms the errors in MNDO were compensated and the AM1 calcns. give satisfactory results: there is a good linear relationship between AM1 calculated results and observed data in gas phase for 7 of the compounds, the linear correlation coefficient being 0.992. The average absolute difference and the average difference between the results are 10.28 and -1.01 kJ/mol, resp.

Key words: FORMATION HEAT, MOLECULAR ORBITAL METHOD, NITRATE