Molecular Structure of <i>N</i>-Methylacetamide as Studied by Gas Electron Diffraction

Abstract The bond distances (rg) and angles (rα) in N-methylacetamide have been determined by gas electron diffraction as follows: C–C=1.520±0.005 Å, N–C (methyl)=1.469±0.006 Å, N–C (carbonyl)=1.386±0.004 Å C=O=1.225±0.003 Å, C–H (average)=1.107±0.005 Å, ∠N–C=O=121.8±0.4°, ∠C–N–C=119.7±O.8°, ∠C–C–N=114.1±1.5°, ∠H–C–H(average)=110.4±2° and ∠H–N–C(carbonyl)=110±5°. In comparison with the molecular structure in the crystal, the N–C(carbonyl) bond is about 0.10 Å longer, whereas the C–C and C=O bonds are about 0.02 and 0.01 Å shorter, respectively. The two methyl groups are in the trans conformation about the N–C (carbonyl) bond, no other conformer being observed.