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8400569 
Journal Article 
The structure of overcrowded aromatic compounds. Part VI.1 the crystal structure of benzo[c]phenanthrene and of 1,12-dimethylbenzo[c] phenanthrene 
Hirshfeld, FL; Sandler, S; Schmidt, GMJ 
1963 
Yes 
Journal of the Chemical Society
ISSN: 0368-1769 
2101-2107 
English 
The crystal structure of benzo[c]phenanthrene has been redetermined by a full three-dimensional X-ray analysis at room temperature, and that of its 1,12-dimethyl derivative has been established by a partial three-dimensional analysis near 80°K. The studies have revealed the principal thermal motions of these molecules, including an appreciable internal vibration in benzophenanthrene, as well as their molecular dimensions. Bond lengths are nearly equal in the two molecules and agree well with the mobile bond orders given by published molecular-orbital calculations; thus any influence of the overcrowding on bond lengths is small. The orientation of the methyl groups in the dimethylbenzophenanthrene is such as to minimise the intramolecular repulsions at the hydrogen atoms.