Molecular structure of propyleneimine studied by gas electron diffraction combined with rotational constants and ab initio calculations

The molecular structure of propyleneimine was determined by a joint analysis of gas electron diffraction data and rotational constants. The results of ab initio calculations were also used as structural constraints in the joint analysis. The ratio of the abundance of trans to cis conformers was fixed at the calculated value, 69 : 31. Mean amplitudes of vibration and shrinkage corrections were calculated on the basis of the vibrational frequencies taken from the literature. The r(z) structural parameters of the trans conformer were determined to be: [r(N-C)] = 1.480(5) Angstrom; r (C-C-ring) = 1.491(14) Angstrom; r (C-C-me) = 1.503(9) Angstrom; r(N-H) = 1.012(18) Angstrom; [r(C-H)] = 1.089(4) Angstrom; angle NCCMe = 116.2(11)degrees; angle CCCMe = 120.7(11)degrees; [angle CNH] = 108.3(22)degrees; [angle XCH(ring)] = 118.5(13)degrees (X = N or C); [angle CCHMe] = 110.5(15)degrees, where [] denotes averaged values. Parenthesized values are the estimated limits of error (3 sigma) referring to the last significant digit.