A SCALED QUANTUM-MECHANICAL FORCE-FIELD FOR TETRANITROMETHANE AND ITSINTERMEDIATES

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 com puted vibrational frequencies fit the experiment within +/- 2 cm(-1). On the other hand, the mechanism of thermolysis of TNM has been invest igated by the mentioned methods and all possible reaction channels hav e been explored. Up to date, we have established that the first step i n the thermal decomposition of TNM involves dissociation of a C-N bond . With this assumption, computed values for the activation energy agre e satisfactorily with the experimental ones. Given that no experimenta l vibrational spectrum is available for transition states, the force f ield for the relevant activated complex has been quantum mechanically computed and then scaled by using scale factors obtained for TNM in it s ground state, then numerical values for the preexponential factor ha ve been computed.