Formamide vibrational frequencies

Florian and Johnson50 calculated vibrational frequencies in isolated formamide using the DFT calculations at the LDA (SVWN) and post-LDA (B88/LYP) levels. The DFT frequencies were compared with the ones derived from the Hartree-Fock and MP2 calculations, and from experiment. The authors found that the DFT(B88/LYP) frequencies were more in line with experiment then the MP2 ones. The DFT(SVWN) calculations led to geometry, force constants, and infrared spectra fully comparable to the MP2 results. The equilibrium geometry and vibrational frequencies of formamide were also the subject of studies by Andzelm et al.51. It was found that the DFT(B88/P86) calculations led to frequencies in a better agreement with experiment than those obtained from the CISD calculations. 

Fig. 6 Amide C = 0 and C-N vibrational frequencies (cm ) and bond lengths (A in parentheses), twist angles (t), average angles at nitrogen computed at HF/6-31G level for ground state and orthogonal conformations of (a) A-formyloxy- /V-mcthoxyformamidc 40, (b) iV-methoxyfomiamidc 41 and (c) formamide 42. Energies (Hartrees) at B3LYP/6-31G // HF/6-31G level.

Fig. 1, Isotope shifts of calculated and observed in-plane vibrational frequencies of formamide. The calculations are at the 4-31G SCF level.

Table 3.80 Frequencies (in cm ) of intermolecular vibrational modes of the formamide dimer. Data calculated at SCF level...

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