MOLECULAR-STRUCTURE OF N,N-DIMETHYLFORMAMIDE FROM GAS-PHASE ELECTRON-DIFFRACTION

The molecular structure of gaseous N,N-dimethylformamide has been determined by electron diffraction, yielding the following bond lengths (r(g)) and bond angles (r(alpha)) with estimated total errors: (C-H)mean, 1.112 +/- 0.003 angstrom; C=O, 1.224 +/- 0.003 angstrom; (C(H3)-N)mean, 1.453 +/- 0.004 angstrom; C(O)-N, 1.391 +/- 0.007 angstrom; N-C=O, 123.5 +/- 0.6-degrees; N-C(O)-H, 117.0 +/- 2.8-degrees; (N-C(H3)-H)mean, 110.1 +/- 0.3-degrees; C(H3)-N-C(H3), 113.9 +/- 0.5-degrees; (C(O)-N-C(H3))mean, 121.6 +/- 0.3-degrees. The experimental results indicate a slight nonplanarity of the nitrogen bond configuration. The angle C(O)-N-C syn to C=O is somewhat smaller than the other C(O)-N-C angle. This and the O...H distance in C=O...H-C, 2.40 +/- 0.03 angstrom, suggest some attractive intramolecular interaction which may influence the methyl torsion in N-methylfomamide and N-methylacetamide, studied by previous experiments.6-9 Similar or shorter O...H distances characterize N,N-dimethylacetamide12 and N-methylacetamide13 according to recent high-level ab initio calculations.