Photolysis of the cis and trans-but-2-enes at 1849 Å

Abstract

The photolysis of either cis-or trans-but-2-ene produces hydrogen, thirty-two hydrocarbon products and a solid polymer. The differing effects of oxygen, nitric oxide and a number of added inert gases on the product yields, enabled the free radical products to be distinguished from the molecular fragments. A mechanism is proposed in which eight possible primary reactions account for the products. All the primary reactions except that which forms the other isomer, may be quenched by increasing the pressure in the system or adding foreign gases, but in the quenching process only the original isomer is formed; there is no change in the amount of isomerization. To explain this result, it is suggested that the initial absorption produces the singlet Rydberg excited state, which may decompose or be deactivated to the original isomer. The isomerization which does occur is not affected by pressure or by the addition of reactive gases, and is thought to occur through the Y(x*, x) state.

The α(C—C)/β(C—H) ratio of the primary processes in the 184.9 nm photolysis of gaseous cis- and trans-2-butene

“…above, fragmentation involves mainly the rupture of either an a(C-C) or a P(C-H) bond (1)(2)(3)(4)(5).…”

“…In these fragments. This excess energy must be partitioned in sets experiments, a stable, thermalized radical abstracts an hydrogen of radicals formed in processes [2] and [3].…”

“…Chesick used a zinc lamp (202.6-206.2 nm) (l), and Borrell et al a mercury one (184.9 nm) (2). Both laboratories investigated the effects of pressure on the total product yields and the product distributions.…”

Excited radicals in the gas phase photolysis of butene isomers at different photon energies: energy distribution in reaction products

“…As shown by many authors (I), these products are formed with a relatively broad spread in internal energy, and the energy need not be statistically distributed among the internal degrees of freedom. It has previously been reported (2,4) that the gas phase photolysis of butene isomers leads to the formation of the C,H,* radicals Can. J. Chem.…”

“…If not collisionally stabilized (process [2]), it either decomposes, yielding allene, or isomerises to the vinylic structure, mhich may be followed by propyne formation. As we have reported previously (51, the last process is a minor one and it will not be discussed in the present paper.…”