Exclusivity of the sp Rotamers of 9-(o-tert-Butylphenyl)fluorene and 9-(o-tert-Butylphenyl)-9-fluorenol in Solution and the Crystalline State

Both 9-(o-tert-butylphenyl)fluorene (C₂₃H₂₂) and 9-(o-tert-butylphenyl)-9-fluorenol (C₂₃H₂₂O) maintained sp rotameric structures exclusively in crystalline form as well as in solution. This result is in contrast to that obtained for the corresponding 9-(o-isopropylphenyl)fluorene and 9-(o-isopropylphenyl)-9-fluorenol. In-plane sterically imposed distortion of the tert-butyl group is exhibited in sp-9-(o-tert-butylphenyl)fluorene and to a much larger extent in sp-9-(o-tert-butylphenyl)-9-fluorenol. The asymmetric unit of the latter contains two crystallographically distinct but nearly identical molecules which are hydrogen bonded to each other via their respective OH groups; hydrogen bonding between the crystallographically equivalent molecules is not observed.

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