The action of red light on solid caryophyllene nitrosite, C15H24N2O3: (i) the reaction products; (ii) the crystal structures of caryophyllene nitrosite and of dinitrocaryophyllene, C15H24N2O4; (iii) electron paramagnetic resonance studies; and (iv) the solid-state reaction mechanisms

Abstract

The stereochemistries of caryophyllene nitrosite (3) and dinitrocaryophyllene (5) have been determined by X-ray analyses of their crystal structures. Crystallographic data are: caryophyllene nitrosite, a=6.476(4), b=13.199(2), c=18.784(2)Å, Z=4, space group P2₁2₁2₁; dinitrocaryophyllene, a=6.405(4), b=12.991(2), c=9.797(3)Å, β=93.04(4)°, Z=2, space group P2₁. The molecular conformations are very similar and caryophyllene nitrosite forms solid solutions in dinitrocaryophyllene. Irradiation of these solid solutions with red light generates a monoalkyl nitroxide radical (11). in two symmetry-related orientations, whose spin- Hamiltonian parameters and orientations in the unit cell of the dinitrocaryophyllene crystal have been determined by detailed analyses of single-crystal e.p.r. spectra. Photolysis of pure solid caryophyllene nitrosite with red light generates N₂, NO, NO₂, dinitrocaryophyllene (5), nitro-nitratocaryophyllene (7), isocaryophyllene (6), and 4,8-bismethylene-11,11 -dimethyl-5-nitrobicyclo[7.2.0]undecane (8) and its isomers, compounds (9) and (10). Three nitroxide radicals, two of which have been identified as compounds (11) and (15) are also generated. The combination of chemical, X-ray, and spectroscopic evidence enables the steps in the solid photolysis reactions to be unravelled.