The thermochemistry of TNAZ (1,3,3-trinitroazetidine)a nd related species:G3(MP2)//B3LYP heats of formation

摘要

The heats of formation of TNAZ(I,3.3-trinitroazetidine) and related compounds have been calculated with the G3(MP2)//B3L YP model to give a mean absolute error of 0.85 kcal/mol for 16 singlet species and 0.61 kcaVmol for 12 free radical intermediates. These uncorrected errors are better than our previous B3L YP/6- 31 G( d,p )-based scheme that employed seven auxiliary parameters. The mean absolute deviation of the G3(MP2)//B3L yp energies of the combined set of 28 singlet and radical species. 0.75 kcaVmol, can be reduced to 0.42 kcal/mol when supplemented with a minimaljour-parameter atom-based correction scheme. It was found that the previous B3L YP/6-3IG(d.p) energies when fitted to a combination of 39 experimental and G3(MP2)//B3L YP singlet and radical species gave a mean absolute deviation of 3.7 kcal/mol. but that the error is reduced to 1.52 kcaVmol when the B3L YP/6-31 G(d.p) energies are supplemented Witll a five parameter additive correction scheme. The results of these calculations are used to clarify the initial mechanistic steps in the decomposition of TNAZ.