A SCALED QUANTUM-MECHANICAL FORCE-FIELD FOR TETRANITROMETHANE AND ITS INTERMEDIATES

The quadratic force field of TNM has been calculated by AM1, PM3 and 3-21G Hamiltonians and then scaled according to Pulay's method. The computed vibrational frequencies fit the experiment within +/- 2 cm(-1). On the other hand, the mechanism of thermolysis of TNM has been investigated by the mentioned methods and all possible reaction channels have been explored. Up to date, we have established that the first step in the thermal decomposition of TNM involves dissociation of a C-N bond. With this assumption, computed values for the activation energy agree satisfactorily with the experimental ones. Given that no experimental vibrational spectrum is available for transition states, the force field for the relevant activated complex has been quantum mechanically computed and then scaled by using scale factors obtained for TNM in its ground state, then numerical values for the preexponential factor have been computed.