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organic compounds
The central rings of 1,2,3,4,7,8,9,10-octahydrochrysene, C18H20, are essentially planar, with the r.m.s. deviation of the atoms defining the plane from the best-fit plane being 0.013 (2) Å. The outer rings are found to be substantially non-planar, contrary to the conclusion of an earlier study based on photographic data [Ferrier & Iball (1958). Acta Cryst. 11, 325-329]. The C-C single-bond distances in the outer rings are quite uniform, with the range of observed values varying by only 0.017 (6) Å. There are no notably close intermolecular approaches.