Density functional studies of molecular structures of N-methyl formamide, N,N-dimethyl formamide, and N,N-dimethyl acetamide

Density functional theory was applied to the calculation of molecular struc tures of N-methyl formamide (NMF), N,N-dimethyl formamide (DMF), and N,N-di methyl acetamide (DMA). DFT calculations on NMF, DMF, and DMA were performe d using a combination of the local functional of Vosko, Wilk, and Nusair (V WN) with the nonlocal exchange functional of Becke and the nonlocal correla tional functional of Lee, Yang, and Parr (BLYP). The adiabatic connection m ethod (ACM) of Becke has also been used, for the first time, for the calcul ation of molecular structures of NMF, DMF, and DMA. The calculated molecula r structures are in excellent agreement with the experimental geometries of NMF and DMA derived from gas-phase electron-diffraction studies. Sparse ex perimental data on the gas-phase geometry of DMF reported in the literature compares well with the DFT results on DMF. DFT emerges as a powerful metho d to calculate molecular structures.