STRUCTURAL INVESTIGATION OF A HINDERED AROMATIC AMINE AND ITS DERIVATIVES

X-ray diffraction structural analysis of N-phenylpiperidine having two isopropyl groups in the ortho (1) and a nitro group in the meta (2) p ositions, has allowed the confirmation of the findings from molecular mechanics calculations on the simple derivative N-(2,6-diisopropylphen yl)piperidine (1) not bearing the nitro group, that the amino function is heavily twisted about the ipso-C-N bond. In addition, there are a number of surprising features like the quasi-planarity of the location of the nitrogen atom and the three carbons attached to it. and the fl attened nature of the isopropyl group. The hydrochloride (3) of 1 exhi bits a peculiar stoichiometry: a hydronium ion coordinates three chlor ide ions, two of them also establish polar interactions with two NH gr oups. A great flattening about the N atoms is observed even in this ca se. The picrate (4) of 1 has the structure of an ammonium salt. Observ ed CN bond lengths both for the amino and nitro groups, which are to b e found in planar and twisted arrangements, raise basic questions abou t the accepted and simplified views and correlations of substituent-ri ng interactions.