Benzophenones, proton exchange

Ghassemi, H., Ndip, G. and McGrath, J. E. 2004. New multiblock copolymers of sulfonated poly(4 -phenyl-2,5-benzophenone) and polyjarylene ether sulfone) for proton exchange membranes. 11. Polymer 45 5855-5862. 

The efficiency of reduction of benzophenone derivatives is greatly diminished when an ortho alkyl substituent is present because a new photoreaction, intramolecular hydrogen-atom abstraction, then becomes the dominant process. The abstraction takes place from the benzylic position on the adjacent alkyl chain, giving an unstable enol that can revert to the original benzophenone without photoreduction. This process is known as photoenolization Photoenolization can be detected, even though no net transformation of the reactant occurs, by photolysis in deuterated hydroxylic solvents. The proton of the enolic hydroxyl is rapidly exchanged with solvent, so deuterium is introduced at the benzylic position. Deuterium is also introduced if the enol is protonated at the benzylic carbon by solvent ... 

The rearrangement of the 5-cyano-4,5-dihydro-l//-azepine (93) to furo[2,3-6]pyridine (95 Scheme 9) with sodium nitrate in glacial acetic acid or with silver nitrate in aqueous ethanol proceeds by initial protonation at either C-3 or C-6 followed by hydrolysis to the cyanooctanedione ester (94). By carrying out the rearrangement with an acid ion exchange resin it is now possible to isolate the dione ester (77CJC4061). Likewise, the hydrolysis of the tetrahydro-2-benzazepine (96) to an 0 -(anilinoalkyl)benzophenone is an example of proton attack at the /3 -carbon of the enamine system (77JA5045). 

Moreover, the larger the radius of the exchange cation, the less predominant the protonated benzophenone species become and the more predominant the hydrogen-bonded benzophenone species become on the surface... 

Proton-deuteron exchange reactions are most easily studied by n.m.r. Examples are the exchange of aromatic protons in phenols under alkaline conditions, exchange of the a-protons in methoxy-acetone in aqueous solution, exchange of NH protons in triethyl-ammonium ion, exchange of the nuclear protons of hydroxy-indoles in deuterium oxide under mildly basic conditions and exchange of aromatic protons of substituted benzophenones in deutero-sulphuric acid. ... 

Not asagned to protons in specific positions. ) Ti= 1,1 10- S, T, = 1,0- 10- sfrom 77---300°K. ) Alkali metal adducts to oxindigo also studied, aU compounds are bridged. Spectra temperatmre dependent, t) Observation of exchange reactions, tt) Numbering of substituent positions see benzophenone-Na. ... 

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