COMBINED MOLECULAR-ORBITALS AND GROUP ADDITIVITY APPROACH FOR MODELING THERMOCHEMICAL PROPERTIES - APPLICATION TO HYDRAZIDES

Heats of formation are often unavailable for compounds involved in syn thesis, scale-up, or modeling of commercial products. This is true for agrochemicals developed at Rohm and Haas which are derived from hydra zides. I have computed heats of formation for five substituted hydrazi des using AM1, HF/6-31G, MP2/6-311G**, and MP4/6-311G**. The computed heats of formation were also used to derive a missing Benson group ad ditivity equivalent for hydrazide. This equivalent makes it possible t o compute heats of formation for hydrazides very easily using group ad ditivity. Molecular orbital calculations are likely to be a valuable s ource for thermochemical information in the future, and this work show s their utility for extending group additivity into new classes of com pounds previously inaccessible due to lack of experimental thermochemi cal data.