Cyanogen, from photolysis

NCCN Photolysis. Cyanogen (NCCN) photodissociation has also been considered a prototypical statistical dissociation reaction. After absorption to the 11,, 1 Au manifolds, the dissociation is thought to proceed via internal conversion to the ground-state surface. Previous studies have measured the rotational state distribution of the CN fragments from photolysis of cyanogen at 193.3 nm [75-77], The threshold photon energy for CN formation was found to be 47,000 200 cm -1 [78]. 

The methyl ester (100, R = CH3), derived from this A-nor acid by treatment with diazomethane, is different from the ester (102) obtained either by Favorskii rearrangement of 2a-bromo-5a-cholestan-3-one (101) or by the action of cyanogen azide on 3-methoxy-5a-cholest-2-ene (103) followed by hydrolysis on alumina. The ketene intermediate involved in photolysis of (99) is expected to be hydrated from the less hindered a-side of the molecule to give the 2j -carboxylic acid. The reactions which afford (102) would be expected to afford the 2a-epimer. These configurational assignments are confirmed by deuteriochloroform-benzene solvent shifts in the NMR spectra of esters (100) and (102). ... 

Milligan and Jacox 44 have recently reported an elegant synthesis of CF2 in an argon matrix. Carbon atoms, produced from the photolysis of cyanogen azide, were allowed to react with molecular fluorine, and the presence of CF2 was demonstrated from infrared spectra. Use of radiation effective in photolyzing F2 produced CF3 from the reaction of the CF2 with atomic fluorine. 

CN radicals appear to have been those of Paul and Dalby , who studied the kinetics of disappearance of CN formed from the flash photolysis of cyanogen under varying conditions. They determined the rate coefficient for the disappearance of CN in the presence of O2 to be 5.5 x 10 I.mole . sec , assuming there was no chain reaction occurring. The nature of the products of the reation was not determined. 

Studies of the photodissociation of cyanogen halides in the vacuum ultraviolet can be separated into two broad types (i) those which employed polychromatic flash photolysis and which were primarily concerned with the detection of electronic and/or vibrational laser action in the CN fragments, and (ii) those which employed continuous monochromatic photolysis sources and were primarily concerned with the branching ratios and energy disposal following dissociation from well-defined initially populated levels. 

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