Hexamethylenetetramine (urotropine) C6H12N2: Interpreting the vibrational spectra of -d0 and -d12 isotopomers by scaling the quantum-chemical force field

The equilibrium structure and quadratic and cubic force fields of the urotropine molecule are calculated at the MP2 (full)/cc-pVTZ level. Pulay scaling of the quadratic force field allows unambiguous interpretation of the vibrational spectra of -d 0 and -d 12 urotropines. A reliable matrix for the quadratic force constants of urotropine is obtained which may be used to determine the parameters of the equilibrium structure of the urotropine molecule by means of gas-phase electron diffraction.