The influence of substituents on the geometry of the cyclopropane ring. VI The molecular and crystal structures of cyclopropanecarboxylic acid and cyclopropanecarbonyl chloride

Crystals of cyclopropanecarboxylic acid, C4H6O2, grown from the liquid are triclinic, space group P1, a = 8.6992(6), b = 8.8017(4), c = 6.6930(3) A, α = 103.71(1), β = 103.93(1), γ = 66.49(1)° (171 K); Z = 4. The final R for 1649 independent observed reflexions [I > 3σ(I)] is 0.037. Crystals of cyclopropanecarbonyl chloride, C4H5OCl, grown from the liquid are monoclinic, space group P21/m. a = 6.287(2), b = 7.092(2), c = 5.647(3) A, β = 101.84(3)° (151 K); Z = 2. The final R for 446 independent observed reflexions is 0.042. The C=O groups in the molecules of both compounds are in the bisecting s-cis conformation. The distal bonds in the cyclopropyl rings have (average) lengths of 1.463(2) and 1.467(2) A, the average vicinal bond lengths are 1.514(2) and 1.516(2) A for the acid and the carbonyl chloride respectively (corrected for libration).