The solution photochemistry of nitroalkenes and nitroketones.

The thesis describes an investigation or the solution photochemistry of nitroalkenes and α-nitroketones, The introduction discusses the general concepts of photochemistry and provides a detailed review of the photochemistry of nitroalkenes, nitroalkanes and nitroaromatics and attempts to relate theoretical studios on the nitro group to the observed photochemistry. Aliphatic α, β-nitroalkenes have been shown to undergo a photoinduced nitro-to-nitrite rearrangement in a variety of solvents, when steric .interactions push the nitro group out of conjugation with the double bond, Nitroalkenes with a secondary or tertiary hydrogen, at the γ-carbon from the nitro group undergo a hydrogen abstraction reaction, which competes with the nitro-to-nitrite rearrangement. Planar nitroalkene3 do not undergo the nitro-to-nitrite rearrangement, but do undergo photoaddition of methanol, when this is used as the solvent. α, β-unsaturated nitroalkenes photochemically add to a variety of alkenes. The adducts resulting from β-nitrostyrene are the most stable. The photoreaction is regiospecific with the most nucleophilic carbon of the alkene attached to the α-position of the β-substituted nitroalkene, out gives in every case a, mixture of stereoisomers. The mechanism of the photoaddition is either concerted or else involves a short-lived diradical .intermediate. Secondary acyclic α-nitroketones undergo photoreactions in a variety of solvents to give hydroxyiminoketones, whore the carbon bearing the oxime group formerly bore the nitro group. This reaction can be rationalized in terms of an initial C-N bond cleavage. Secondary acyclic α-nitroketones on refluxing in alcohols and ethers give hydroxyrminoketones, solvent oxidation products and fragmentation products. This reaction was again rationalised by an initial C-K bond cleavage, 2-Nictocyclohexanone undergoes a ring cleavage reaction on refluxing in alcohols, via a hemi-acetal intermediate