The forination of the c>nol f~i i of acetone in the "type I I " pri~iiary photochemical process in methyl ketones containing ~-liydrogcn atc~nis has received general :tcceptunce in recent yearb on the basis o f published indirect evidence. I n tliis work a direct observation of the t r a n i i c~~t m o l for111 of acetone has been made by infrared absorptioii during the pliot,Jysis of 2-pentanone. The mo1 + kcfo conversion was studied by following both the disappcaraiice o f the enol a n t l tlic appeararicc o f the k/,ln form using Ioiig-path iiifrarcd tecli~iiques. The half-life of rnol-acetone is ctl)out ;3 3 i n i n a t ' 2; " anti 750-niiii total pressure. The ketonization process seems to occur inainly a t the rcaction Photolyses of 2-per1tanone were also carried out in sn~all reaction vessels pretreated witli 1)d) I n this case tlic kr~l+;icetone ultiiiiately priiducrd I S partly inonodeuterated, and a partial escliange o f the P U O ! forin a t tlie vessel wall is indiczctcd ; this result is siniilnr to t h a t reported by Srinivasan in en~~erinients wit11 2-Iicx:iii~~nc. The extent of exchange exhibits a peculiar depcndcnce on the residence tiirie i n the cell which coiiiplic:~tes the interprctatiori o f the ket~~nization step under these conditions. .el wall.
A B S T R A C T T h e photolysis o f di-1-butyl peroxide has been investigated over t h e teniperature range 25"t o 7g0 C. As reactio~l products were observed : acetone, t-butyl alcohol, methyl t-butyl ether, i-butylene oxide, ethane, methane, and
carbon monoxide. T h e follo~ving reactions, involving t h e t-butoxy radical, have been studied:A n activation energy difference o f E ? -E 6 = 3 lccal has been obtained.
I N T R O D U C T I O NPrevious work (1, 2, 3) on the photolysis of di-t-butyl peroxide has established that the primary process consists of the breakage of the 0--0 bond, thus producing two t-butoxy radicals. I t could also be sholvn that the t-butoxy radical is relatively unstable and decomposes according to reaction [2] :As most recent values for the activation energy of reaction [' I have been reported 11.2&2 (3) and 1 3 . 2~t 2 . 4 (4) ltcal.Such a value for E? ivould, however, indicate that especially a t low temperatures the t-butoxy radical might survive long enough to taltc part in abstraction and recombination reactions. While the formation of t-butyl alcohol through hydrogen abstraction b y t-butoxy radicals has been reported frequently (5, 6) no illformation was available regarding the activation energy for the abstraction of a hydrogen atom from di-t-butyl peroxide. In the photolysis of di-t-butyl peroxide a considerable amount of ethane is produced by recombination of methyl radicals, originating from reaction [2]. I t seemed, therefore, likely that especially a t low temperatures some methyl t-butyl ether might be produced via recombiilatioil reactions, although this compound had thus far not been reported among the reaction products. I n order to clear these questions the photolysis of di-t-butyl peroxide has been studied again.
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