ROTATIONAL ISOMERS AND MOLECULAR-STRUCTURES OF (E)-PROPIONALDEHYDE OXIME AS STUDIED FROM ELECTRON-DIFFRACTION AND MICROWAVE SPECTROSCOPIC DATA

The molecular structures of two rotational isomers (anticlinal and syn periplanar forms) of gaseous (E)-propionaldehyde oxime have been deter mined from electron diffraction and microwave spectroscopic data. The anticlinal form is more stable by 0.15 +/- 0.10 kcal mol(-1) than the synperiplanar form. The molecular parameters of the anticlinal form ar e r(g)(C-1-C-2)=1.552(3) Angstrom, r(g)(C-2-C-3)=1.493(2) Angstrom, r( g)(C-3=N)=1.284(2) Angstrom, r(g)(N-O)=1.429(2) Angstrom, angle C1C2C3 =111.5(1)degrees, angle C2C3N=119.0(3)degrees, and angle C3NO=109.4(2) degrees. The angle C2C3N, angle C1C2C3, and r(g)(C-3-N) values of the synperiplanar form (122.6(6)degrees, 112.6(6)degrees, and 1.291(3) Ang strom, respectively) are not equal to those of the anticlinal form.