Magnetic resonance studies of the structure and the red photolysis reactions of 2-chloro-2-nitrosonorbornane

Abstract

Detailed NMR studies have shown that at 298 K optically-inactive saturated blue solutions of 2-chloro-2nitrosonorbornane in CDCl₃ contain a mixture of the monomeric and dimeric forms of the compound in a ratio of dimer : monomer = 1: 40 (± 2): this ratio changes with a change in temperature. The analysis assigns the configuration at the C(2)(NO)(Cl) centre and shows that the monomeric form has the structure (4), in which the NO group is on the same side of the molecule as the bridging C(7)H₂ group. White, solid 2-chloro-2-nitrosonorbornane is a 1:1:1:1 mixture of four diastereoisomeric forms of trans-diazodioxide (5). The white solid readily sublimes at ambient temperature and monomeric vapour forms a blue–green cast on its surface. Red-irradiation of the compound, in vacuo, produces white crystals and a viscous brown oil. The white crystals contain norbornan-2-one (6), the syn- and anti-forms of the norbornan-2-one oximes, (7) and (8), and a lactam, (9). These compounds are present in the viscous brown oil which also contains three other compounds to which the structures (10), (11) and (12) are assigned. The reaction mixture is EPR silent. The spectroscopic evidence enables some of the steps in the red photolysis reactions of (4) to be unravelled.