Radical Yields in the Radiolysis of Branched Hydrocarbons:  Tertiary C−H Bond Rupture in 2,3-Dimethylbutane, 2,4-Dimethylpentane, and 3-Ethylpentane

Abstract

Gel permeation chromatography has been applied to iodine scavenging studies of the distribution of radicals produced in the radiolysis of symmetrically branched hydrocarbons 2,3-dimethylbutane, 2,4-dimethylpentane, and 3-ethylpentane. The principal iodides observed are those expected as a result of simple bond rupture. In the case of 2,3-dimethylbutane all five expected iodides are readily resolvable and it is shown that the loss of H from a tertiary position is favored over loss from a primary position by a factor of ∼10. A similar ratio is also observed for 2,4-dimethylpentane. The higher ratio of 15 observed for 3-ethylpentane indicates a dependence on the number of tertiary sites on the alkane. The relative yield of ∼3.3 for the loss of secondary and primary H atoms from 2,4-dimethylpentane and 3-ethylpentane is similar to that for normal alkanes, indicating a negligible effect of the adjacent tertiary carbon. In all three cases the rupture of terminal C-C bonds is relatively infrequent with C-C rupture occurring preferentially at the bonds adjacent to the tertiary carbon.

Structural changes on citronellol induced by gamma radiation

“…Dihydrocitronellol percent increases from sample A to B, until 1.61%, and then at 1.75% in sample C, being constant in sample D. This supports the fact that radical Ḣ participates in the radiolytic transformations of citronellol, [20,21] because dihydrocitronellol is the product of citronellol's hydrogenation, which could be performed by hydrogen radical. It must be pointed out that the most abundant compounds formed from citronellol by the action of gamma radiation were Nid1 and hydroxycitronellal in the sample D (3%).…”

“…It is in agreement with previous reports that ionizing radiation acts preferably on the functional groups of the organic compounds. [20,21] In addition, the stability rules of radicals (tertiary > secondary > primary) was considered, as the most stable radicals have more probabilities of participating in the formation of final products of radiolysis. [18][19][20][21] Oxidation mechanism of citronellol Previous theoretical studies about citronellol oxidation to citronellal were not found, neither of similar compounds.…”

“…[20,21] In addition, the stability rules of radicals (tertiary > secondary > primary) was considered, as the most stable radicals have more probabilities of participating in the formation of final products of radiolysis. [18][19][20][21] Oxidation mechanism of citronellol Previous theoretical studies about citronellol oxidation to citronellal were not found, neither of similar compounds. However, two mechanisms are proposed for the formation of an aldehyde starting from the corresponding primary alcohol, induced by ionizing radiations.…”

Solid phase extraction of tritiated contaminants from tritium-containing waste oils

“…The initial step in this mechanism is the formation of parent alkyl radicals, which in our case can proceed via the abstraction of a H atom by an oxygen-centered radical or by a -irradiation-induced C–H bond rupture. Both processes are expected to be quite selective, producing preferentially tertiary alkyl radicals [32–34]. These radicals, in a series of subsequent reactions involving dioxygen addition, H atom abstraction, and dissociation of the resulting hydroperoxide, give rise to the formation of tertiary alkoxyl radicals (Reaction 1, Scheme 1), which in turn might decompose via -scission (Reaction 2), resulting in the formation of the fragmentary products: methyl ketone and primary alkyl radical.…”