ABINITIO STUDY OF THE FORCE-FIELD AND VIBRATIONAL ASSIGNMENT OF N-ACETYL-N'-METHYLALANINAMIDE

The quadratic force field of N-acetyl-N′-methylalaninamide (AMAA) has been calculated at the ab initio Hartree-Fock level by using a 4-21 basis set. On the basis of this, a thorough discussion is presented on the previously observed vibrational spectrum in argon matrix. It is shown that the matrix contains this molecule in the C7eq form, which is also known to be the most stable conformer in the isolated state. Evidence for the presence of the same conformation in the solid phase is demonstrated by the vibrational spectrum. Similarly, evidence is presented for the presence of the same conformer in the solid phase of N-acetyl-N′-methylglycinamide. © 1990 American Chemical Society.