Redetermination of 2-propenoic acid at 125K

Abstract

The title compound belongs to the family of α,β-unsaturated carboxylic acids having a Z conformation. The packing is characterized by layers of O—H···O hydrogen-bonded dimers. Comment The structure of the title compound was determinded by x-ray analysis twice in 1963, by Chatani et al. (1963), where no R value is given, and as well by Higgs et al. (1963) with an R value of 0.102. The bond-distance data about the C—O bonds are contradictory. Thus a need for a redetermination is obvious. The title compound belongs to the family of α,β-unsaturated carbonic acids in Z conformation. The packing is characterized by layers of dimers with hydrogen bonds H1···O2'. The molecules within a layer interact through weak C—H···O contacts with 2.32 and 2.59A for the H···O distances (C—H normalized to 1.08 A). The corresponding angles are 155.4 and 146.8°. Additional characteristic atom distances of the dimer are: O1—O2': 2.6529 (9)A (intermolecular); H1—O2': 1.8679 (264)A (intermolecular); O1—H1: 0.79 (3) A; C1—O2: 1.2318 (9) A; C1—O1: 1.3205 (8) A. The C1—O2 bond distance is slightly longer than the standard distance range for carbonic acids of 1.205–1.215 A. The C1—O1 bond distance is also slightly longer than the standard distance of 1.308 A.