Propylene triplet state

Since rapid reaction is expected and found between oxygen and molecules excited to their triplet state (i.e., 0.01 mm. oxygen has a marked effect) a less pronounced effect, such as is observed with 2-pentanone, may naturally be ascribed to a reaction with excited singlet states. The evidence is not conclusive, but the addition of 560 mm. oxygen to 2-hexanone at room temperature using 3130 A. radiation resulted in only a slight decrease in the acetone and propylene yields, so that Brunet and Noyes2 concluded that an excited triplet state was not involved in the type II process. Recent evidence from other sources seems to support this point of view. (Editor s Note Added in Proof However, a recent article by Ausloos and Rebbert [J. Am. Chem. Soc., 86, 4512(1964)] indicated that the type II process occurs via a triplet excited state.)... 

Vibration-vibration energy transfer in SOa has also been discussed.390 The SOa-sensitized cis-trans isomerization of but-2-ene is a complex reaction, which at low pressures can be explained as involving only the ZBX state of S02, but which at higher pressures requires the intervention of some triplet state other than the phosphorescent SBX level.391 The photolysis of S02 in the presence of acetylene and allene also involves these non-phosphorescent triplet states, yielding CO as product, and giving rise to aerosol formation.392 Aerosol formation in S02-N2-02 mixtures has been experimentally investigated,393 and the effects of N02, propylene, and water on SOa reactions have been reported.884 Interactions between S02 and atmospheric particulate matter,395 photochemical removal of SOa from the lower atmosphere,396 the use of SOa to trap 1,4-biradicals generated photo-chemically,397 and the photochlorination of S02 398 have all been discussed in recent publications. 

DeGraff and Calvert (66) have carried out careful steady-state photolyses of H2CO and D2CO with added pressures of propylene, neopentane, and biacetyl at 334.0, 313.0, 265.4, and 253.7 nm. Propylene was used as an olefinic radical scavenger, neopentane as an "inert" gas for vibrational deactivation, and biacetyl as a possible triplet energy acceptor. 

Photolysis.—Photochemical transformations of thietan derivatives have not received much attention, but it appears that the initial process is homolysis of a C—S bond, and that extrusion of sulphur is not important, in contrast to the case for thiirans. A reversed [2 + 2]cycloaddition may occur via initial homolysis of the C—S bond, 2,2-diphenyl-3,3-dimethyl-4-isopropylidenethietan, for example, giving l,l-diphenyl-2,2-dimethyl-ethylene, and rra j-2-phenyl-3-benzoylthiiran being converted into a mixture of cis- and /mns-benzalacetophenone, probably by way of its triplet excited state. Thietan vapour on photolysis gave mixtures containing ethylene, propylene, and polymer, and on prolonged irradiation, 2-methylthiiran. ... 

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