Preparation and Properties of Molecules Having High Steric Crowding. 1,8-Diphenylnaphthalenes

Citation

Clough, Roger Lee (1975) Preparation and Properties of Molecules Having High Steric Crowding. 1,8-Diphenylnaphthalenes. Dissertation (Ph.D.), California Institute of Technology. doi:10.7907/B8WV-Q285. https://resolver.caltech.edu/CaltechTHESIS:12122017-144229583

Abstract

The 1,8-diarylnaphthalenes have distinctive properties and geometric features which result from the forced proximity of the adjacent periaryl rings. We have developed an efficient synthetic route to 1,8-diphenylnaphthalene derivatives which involves a direct coupling between the phenyl and naphthyl rings with an organonickel catalyst. The magnitude of the strain energy resulting from the overcrowding in 1,8-diphenylnaphthalene 1 is determined using combustion calorimetry. An X-ray analysis of peri-diphenyl- acenaphthene 2 is reported. The over crowded phenyl rings of 2 are face to face and nearly perpendicular to the naphthalene ring plane. Large structural distortions are found, especially in the naphthalene framework. A comparison of the geometries of several 1,8-diphenylnaphthalenes having different types of steric interactions at the 4,5 positions is made, and an analysis of distortions in terms of induced stress vectors which act throughout the naphthalene framework is presented. Striking effects in both the proton and C-13 nmr spectra of derivatives of 1 are found which are correlated with a near-perpendicular solution conformation of the phenyl and naphthyl rings.

The phenyl rings in derivatives of 1 have surprisingly low barriers to a 180° rotation about the phenyl-naphthyl bond. Comparison of rotational barrier measurements for analogs and derivatives of 1 including the highly strained 1,4,5,8-tetraphenyl-naphthalene, together with other observations, indicates that the transition-state to phenyl-ring rotation involves substantial concurrent warping of the naphthalene ring as a whole. Substitution in the phenyl­-ring ortho position raises the rotational barrier considerably; cis and tram rotational isomers of 1,8-di-o-tolylnaphthalene are isolated and studied.

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