A study of the molecular structure of monochloro-acetic acid by means of gas electron diffraction

Abstract

The results of an interpretation of the gas electron diffraction pattern of monochloroacetic acid at 170 °C and a microwave investigation by Van Eijck et al. from this laboratory were combined. Three conformations with respect to internal rotation around the C—C bond were found, viz. 56% of a conformation with C5 molecular symmetry and the C—Cl bond eclipsed with the C=O bond, 30% of a conformation with the CH2Cl group rotated 131° from the former position and the remaining 14% of a conformation with 79° rotation of the CH2Cl group. The bond lengths and the bond angles determined by means of this procedure are (standard deviations in parentheses): C—Cl: 1.778(0.005), C—C: 1.508 (0.006), C=0:1.223(0.004), C—0: 1.352(0.005), C—H: 1.09(0.02), O—H: 0.97 (0.015) Å; C—C=O: 126.1(0.5), C—C—O:110.6(0.4), C—C—C1:112.5(0.4), C—O—H: 105.8(1.1)°. A conformational distribution obtained by means of CNDO/2 calculations is not in agreement with our experimental radial distribution.