Molecular structure of 1,2-dimethyl-1,2-diazetidine. Electron diffraction and microwave study and normal coordinate analysis

Abstract

The molecular structure of 1,2-dimethyl-1,2-diazetidine has been studied in the gas phase by joint analysis of electron diffraction and microwave data. Infrared, far infrared and Raman spectra were assigned and a force field derived. The orientation of the methyl groups is (quasi-) equatorial–equatorial and the following geometric parameters (r_av values) were obtained for the molecular skeleton assuming C₂ symmetry: N—N = 1.427(7)Å, C—C = 1.537(11)Å, C—N_endo= 1.481(8)Å, C—N_exo= 1.471(7)Å, ∠C_methylNN = 113.0°(6), dihedral angle δ(C_methylNNC_methyl)= 105.3°(8) and ring puckering angle ϕ(CNCN)= 24.3°(6). Error limits are 3σ values of the least-squares analysis. The result of this structure study agrees well with predictions from photoelectron spectroscopy.