PHOTOLYSIS OF NITRATE ESTERS—II. SOLUTION PHOTOLYSIS OF ARALKYL NITRATE ESTERS: KINETICS, ESR SPECTRA, AND PHOTOPRODUCTS

Abstract— Irradiation of benzyl nitrate, meso- and dl-hydrobenzoin dinitrates, and cis- and trans -1,2-acenaphthenediol dinitrates in benzene solutions 0.02M in nitrato groups at 265–313 mp decomposed the esters with a quantum yield of 0.4±0.2 in reasonable agreement with earlier work on the gas-phase photolysis of ethyl nitrate. An important primary process was ArRCHONO₂+h v ArRCHO +NO₂, although ArRCHONO₂+h v ArRCHONO + O was not excluded. In secondary reactions solvent benzene was oxidized and nitrated, aldehydes were formed from the nitrate esters, and nitric oxide was evolved. The higher quantum yields of the photodecomposition in ethanol (0.8±0.3) and ether (3±1) solutions were interpreted in terms of a charge-transfer state similar to that found with nitroalkanes in these solvents. Acetaldehyde was produced in a rapid secondary reaction in alcohol solutions at 25° and at 77° K, NO₂ was identified as an intermediate from the ESR spectrum. No stereospecificity was detected in a comparison of rates, photoproducts, and ESR spectra for the stereoisomers. The overall results indicated inter- rather than intramolecular migration of oxy-nitrogen groups in secondary reactions. An apparently new, long-lived, oxynitrogen radical was detected in benzene solutions of nitric oxide and nitrate esters irradiated at 25°.