X-ray Crystallographic Structure of 3-(Propan-2-ylidene) benzofuran-2(3H)-one

Abstract

3-(Propan-2-ylidene)benzofuran-2(3H)-one, C₁₁H₁₀O₂, crystallizes in the monoclinic space group P2₁/c with unit cell parametersa =7.1869(3), b = 18.0636(10), c = 13.1656(7) b= 96.763(3), V =1697.28(15) , Z = 8 (Z? = 2 independent molecules, A and B, per asymmetric unit), D_c = 1.363 g cm^-3 and the linear absorption coefficient = 0.093 mm^-1. The crystal structure determination was carried out using MoKa X-ray data measured at 120(2) K. In the final refinement cycle the data/restraints/parameter ratios were 3827/0/239, the goodness-of-fit on F2 = 1.019. Final R indices for [I>2sigma(I)] were R1 = 0.0517, wR2 = 0.1115 and R indices (all data) R1 = 0.1007, wR2 = 0.1354. The largest electron density difference peak and hole were 0.254 and -0.244 electrons sup>-3, respectively. The two independent molecules A and B have essentially identical bond lengths and angles and are highly planar, with rms deviation for all 12 non-H atoms of 0.0292 for molecule A and 0.0592 for molecule B. The two molecules in the asymmetric unit are assembled parallel to each other within 1.58(4) with each of the six atoms of benzene ring A overlapping with one of the atoms in benzene ring B at a mean distance of 3.84(3) . The closest contacts between molecules A and B are C(12A)H---O(4B) = 3.521 and C(11B)H---O(4A) = 3.441 The crystal structure is formed by infinite sheets of these assemblies all lying parallel to the (1 0`1) plane. The presence of two independent molecules in the asymmetric unit provides an opportunity to examine the molecular geometry in detail by comparison. The benzene ring in both molecules A and B exhibits distortions as a result of the presence of the furan moiety. In particular, C(1)-C(6) = 1.369(2) in molecule A and 1.367(2) in molecule B are both significantly less than the average of the other 10 C-C bonds, 1.393(2), by about 12?. Other examples of crystal structures are discussed where this effect is observed.