Structure of 6-acetoxycoumarin: topochemical photodimerization and analysis of acetoxyacetoxy interactions in the solid state

Abstract

C₁₁H₈O₄, M_r=204.2, monoclinic, P2₁/n, a=3.900 (1), b=37.530 (6), c=6.460 (1) Å, β=103.7 (1)°, V=918.5 (5) ų, Z=4, D_m=1.443, D_x=1.476 Mg m^-3, Cu Kα, λ=1.5418 Å, μ = 0.86 mm^-1, F(000)=424, T=293 K, R=0.075 for 1019 significant reflections. Molecules pack in β-type stacking mode which is characterized by the close packing of parallel and nearly planar reactive double bonds with a separation of 3.900 Å along the α axis.The syn head-head dimer obtained is the direct consequence of this packing arrangement. Molecular packing is stabilized by intermolecular C-H†O hydrogen bonding. Analysis of acetoxy ···acetoxy interactions in the acetoxy compounds retrieved from the Cambridge Structural Database reveal that the majority of them are anti-dipolar.