58142-37-3Relevant academic research and scientific papers
Radical ions in photochemistry. Carbon-carbon bond cleavage of radical cations in solution: Theory and application
Popielarz,Arnold
, p. 3068 - 3082 (1990)
The cleavage of radical cations of two series of alkanes, 1,1,2-triaryl- and 1,1,2,2-tetraarylalkanes, generated by photoinduced single electron transfer in acetonitrile-methanol, occurs with formation of radical and carbocation fragments. The radical cations of some unsymmetrically substituted alkanes cleave to give all four of the possible products, two hydrocarbons emanating from the radicals and two methyl ethers from the carbocations, in proportion to the oxidation potentials of the two possible radical fragments. There is an excellent linear correlation between the logarithm of the observed ratio of products and that calculated from the reported electrochemically determined oxidation potentials (r = 0.998, 5 points). The proportionality constant (1.27) for this relationship is close to unity which indicates that the product ratio is determined by the relative rates of cleavage in the two possible modes or by equilibration of the radicals and carbocations before separation of the geminate radical carbocation pair and not by equilibration upon reencounter of freely solvated radical and carbocation fragments. The effect of temperature on the relative oxidation potentials of the radicals studied is small and can be neglected when radicals of the same order (i.e., both secondary or both tertiary) and of similar size are compared. The ratio of products obtained upon cleavage of the radical cation at 25 °C can be used to determined standard oxidation potentials of radicals. The oxidation potential of the diphenylmethyl radical (0.350 V vs SCE) has been accepted as the primary standard and the (4-methyl-phenyl)phenylmethyl (0.265 V) and bis(4-methylphenyl)methyl (0.188 V) radicals are established as secondary standards against which the oxidation potentials of other radicals can be measured. Oxidation potentials of several 4-substituted cumyl radicals have been determined by this photochemical method. There is a good (r = 0.987, 5 points) linear correlation between the measured oxidation potentials and the σ+ substituent constants. The reaction constant is appropriately negative and large (p = -6).
Transient Kinetics and Quantum Yield Studies of Nanocrystalline α-Phenyl-Substituted Ketones: Sorting Out Reactions from Singlet and Triplet Excited States
Park, Jin H.,Chung, Tim S.,Hipwell, Vince M.,Rivera, Edris,Garcia-Garibay, Miguel A.
supporting information, p. 8192 - 8197 (2018/06/22)
Recent work has shown that diarylmethyl radicals generated by pulsed laser excitation in nanocrystalline (NC) suspensions of tetraarylacetones constitute a valuable probe for the detailed mechanistic analysis of the solid-state photodecarbonylation reaction. Using a combination of reaction quantum yields and laser flash photolysis in nanocrystalline suspensions of ketones with different substituents on one of the α-carbons, we are able to suggest with confidence that a significant fraction of the initial α-cleavage reaction takes place from the ketone singlet excited state, that the originally formed diarylmethyl-acyl radical pair loses CO in the crystal with time constants in the sub-nanosecond regime, and that the secondary bis(diarylmethyl) triplet radical pair has a lifetime limited by the rate of intersystem crossing of ca. 70 ns.
