The Molecular Structure of 1,2-Dichloropropane

Under the assumption of V([open phi])=V_0[1—cos([open phi]—[open phi]_0)] / 2 for the potential hindering internal rotation, visual interpretation of the electron‐diffraction pattern leads to the results (best values and estimated limits of error): C–Cl, 1.79±0.035A; C···Cl, 2.715±0.025A; C–C, 1.56A (range: 1.49–1.60A); ∠C–C–Cl, 108±4°; |[open phi]_0| ≤ 30° (i.e., essentially trans in the chlorine atoms), with a small positive value of [open phi]0 (increasing CH_3···Cl primary ) most likely; V 0≥4 kcal/mole. The best value for V_0 ranges from 10 kcal/mole for [open phi]0=0° to 30–40 kcal/mole for [open phi]_ 0 = 25°. The diffraction pattern is almost indifferently compatible with fractions ranging up to 50 percent of a skew‐isomer with [open phi]_0 ∼ 120° and a sufficiently low value of V_0, but consideration of dipole moment data provides some further evidence on its structure while showing the fraction present to be about 20 percent with an upper limit of about 30 percent.