Photolyse du butyne-2 dans la région de l'uv sous vide

The vacuum uv photolysis of gaseous 2-butyne has been studied at 147, 163, and 174 nm. The use of hydrogen iodide as radical scavenger shows the importance of methyl radical formation in the fragmentation of the photoexcited molecule. It is concluded that the principal fragmentation of the photoexcited molecule involves the cleavage of a C—CH 3 bond: [Formula: see text] and [Formula: see text]. Unfortunately, it was not possible to scavenge the corresponding C 3 H 3 radicals. From the fast decrease of the transparency of the window it is concluded that an important radical polymerization takes place, even in the presence of oxygen or nitric oxide. Finally, from the pressure effect, it is shown that propyne results from the fragmentation of the vibrationally excited butenyl radical and vinylacetylene arises from the fragmentation of an excited C 4 H 5 radical.