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• 1013-88-3 Benzophenone imine 

Relevant academic research and scientific papers

Exploitation of aldoxime esters as radical precursors in preparative and EPR spectroscopic roles

Photolyses of aldoxime esters, containing a considerable range of alkyl groups, lead to cleavage of their N-O bonds and formation of aryliminyl and alkyl radicals. The process was found to be favoured by 4-methoxyacetophenone as a photosensitiser and by methoxy substituents in the aryl rings. 4-Nitro- and pentafluoro-substitutions of the aryl rings were, on the other hand, deleterious. The intermediate iminyl radicals, together with primary, secondary and tertiary alkyl radicals were characterised by 9 GHz EPR spectroscopy. Cyclopropyl, CF3, and CCl3 radicals were probably also formed, but were too reactive for direct EPR spectroscopic detection. Photosensitised reaction of benzophenone oxime O-nonanoyl ester produced the diphenylmethaniminoxyl, as well as the expected n-octyl and iminyl radicals. This indicated that O-C bond scission accompanied O-N scission for this ketoxime ester. At higher temperatures the C-centred radicals added to the starting oxime esters to produce alkoxyaminyl radicals that were also spectroscopically detected in some cases. No evidence for abstraction of the iminyl hydrogen by tertbutoxyl radicals was obtained. Instead, the t-BuO radicals added to the C=N double bonds of the oxime esters. Similarly, chlorine abstraction from alkylbenzohydroximoyl chlorides by trimethyltin radicals did not take place. Preparative scale experiments with oxime esters containing suitably unsaturated alkyl groups showed that good yields of cyclised products could be obtained in the presence of the photosensitiser. This process constitutes a general method by which carboxylic acids or acid chlorides can be converted into alkyl radicals and hence to cyclised derivatives.

Electron Paramagnetic Resonance Study of Imine Radical Cations in Low-temperature Solid Matrices

A series of imine radical cations has been studied by EPR spectroscopy, generated in low-temperature halogenocarbon matrices by γ-radiolysis.Radicals of the type ArCH=NR.+ tend to be formed in the 2A'state, corresponding to ionisation of the in-plane (mainly the nitrogen lone-pair) a' orbital (I).These are isostructural with the corresponding vinyl radicals and show angular geometries at the radical centres and large couplings (ca. 85 G) to the proton trans to the nominally nitrogen-localised SOMO (I).When R = But, a 12 G long-range coupling is observed to a single proton from the But group, arising via the W-configuration (II).This coupling was found to persist in the CFCl3 matrix up to its melting point (ca. 160 K), but was lost reversibly in the higher melting CCl4 matrix at ca. 200 K. When R = phenyl, the radical centre is rendered linear, because of the partial ?-bonding between the aromatic ring and the nitrogen atom due to delocalisation of the unpaired electron, as shown by a fall in the parallel (14N) coupling with a concomitant increase in the nitrogen 2p/2s ratio, and by the observation of couplings to the ortho and para phenyl protons. For imines derived from benzophenone (Ph2C=NR) the tendency is for ionisation to occur from the ?-orbital (III) which has large spin densities on the para carbon atoms. Benzophenone imine (Ph2C=NH), in addition to forming the ?-state (III), was found to deprotonate, giving rise to the Ph2C=N. radical.Similar behaviour was shown by benzophenone oxime, which gave only the corresponding iminoxyl radical (Ph2C=N-O.), and we propose that this is due to the dissolution of the latter two materials in the form of hydrogen-bonded molecular clusters in the non-polar freon solvent, thus facilitating deprotonation of the primary cations.