The conformations of 1,2-acenaphthene derivatives and steric interaction of contiguous nitroxy groups

Inter-oxygen distances and conformational flexibility were estimated for cis- and trans-1,2-acenaphthenediol from X-ray data, intramolecular hydrogen bonding, the kinetics of glycol cleavage, and cyclization experiments. The optical and NMR spectra of the isomeric dinitrate esters and related compounds in solution showed significant differences. The symmetric and anti-symmetric stretching bands of the nitroxy group occurred at 1276 ± 2 cm^?1 and 1639 ± 7 cm^?1 respectively in the trans-dinitrate and in ethyl and benzyl nitrates and were shifted to higher frequencies by 9 cm^?1 and 16 cm^?1 respectively in the cis-dinitrate. The analogy to similar effects observed in cyclic 1,2-diketones, -haloketones, and o-halonitrobenzenes suggested intramolecular interaction of the contiguous nitroxy groups.

The reaction of the dinitrates with pyridine at 25° was pseudo first-order and the ratio k_trans/k_cis of 6·5 was consistent with an E_CO mechanism involving nitroxy group interaction in the cis isomer.