X-ray studies of terpenoid derivatives. Part I. The crystal and molecular structure of humulene bromohydrin

Abstract

The tricyclic bromodydrin of humulene, C₁₅H₂₅OBr, is monoclinic, space-group P2₁/n, with unit-cell dimensions: a= 6·07 Å, b= 19·54 Å, c= 12·39 Å, β= 93·47, and four formula units per cell. The crystal structure has been elucidated by a full three-dimensional X-ray study, based on 1922 independent reflection intensities, visually estimated from Weissenberg photographs. The bromine atom was used as a phase-determining heavy-atom; positional and anisotropic thermal parameters have been refined by block-diagonal least-squares methods to a final R-factor, for observed reflections only, of 0·100. The originally suggested stereochemistry has been corrected. The geometry and conformation of the fused ring system is discussed in some detail.