Application of spin trapping to the detection of radical intermediates in electrochemical transformations

Abstract

620 0 0 10 cis and trans cis and t r a n s 11From these observations we conclude that the rearrangements of a-methylene ketones generalized in eq 3 and 4 involve singlet biradical intermediates. l 1 For the y-hydrogen abstraction leading to cyclobutyl ketones these intermediates must have a lifetime sufficient to permit the rotatim about the cr,p carbon-carbon bond required for ring closure. It is noteworthy in this regard that evidence is on record favoring short-lived biradical intermediates in the singlet y-hydrogen abstraction reactions of saturated alkanones12 and also implicating longer-lived singlet biradicals as intermediates in the related abstraction processes of P , y unsaturated ketones. l 3 , I 4 (1 1) A theoretical discussion detailing the oversimplifications inherent in use of simple structures for such species is given by L. Salem and C. Rowland, Angew. Chem., 84, 86 (1972); Angew. Chem., Int. Ed. Engf., 11,92 (1972). (12) L. M. Stephenson, P. R. Cavigli, and J. L. Parlett, J . Amer. Chem. Soc., 93, 1984 (1971); C. P. Casey and R . A. Boggs, ibid., 94, 6457 (1972). (13) J. C. Dalton and H.-F. Chan, J. Amer. Chem. Soc., 95, 4085 (1973). See also P. S. Engel and M. A. Schexnayder, ibid., 94, 9252 (1972).

In silico rational design by molecular modeling of new ketones as photoinitiators in three-component photoinitiating systems: application in 3D printing

“…The simulation gave the following hfc constants for the PBN spin adducts: aN = 14.8 G; aH = 2.8 G, and a radical is detected: (CH3)3C6H4• which fully match to literature data. [34] This suggests the redox reaction (r2) between ketone/Iod while Iod acted as an oxidizer leading to aryl radicals.…”

Spin trapping in heterogeneous electron transfer processes

“…Spin trapping (1,2) with various nitroso and nitrone derived moieties has proven to be a fruitful approach to the detection and characterization of transient radical intermediates ensuing from electrooxidations (3-6), photoassisted oxidations (7)(8)(9), and electroreductions 'Present address: Research Laboratories, Eastman Kodak Company, Rochester, NY 14650, U.S.A. 2 Authors to whom correspondence should be directed. (4,(10)(11)(12) of various substrates in solution. The viability of spin trapping as an investigative tool in electron transfer processes requires that (i) the spin trap reagent be electroinactive at potentials required to discharge the substrate, (//) the rate of reaction of radical intermediates with the spin trap be favorable relative to those of other radicalconsuming reactions, and (Hi) the product of the radical/spin trap reaction (the spin adduct) also be electroinactive at potentials which are employed to oxidize or to reduce the substrate.…”

Modification of Carbon Electrode Surfaces

“…The chronoamperogram is also very characteristic as instead of following the Cottrell law that describes the current decrease expected for the reduction of electroactive species in solution, one observes a rapid drop of the current that is related to the blocking of the electrode. The involvement of radicals during the electrochemical reduction of aryldiazonium salts was demonstrated through the Pschorr synthesis of phenanthrene [40] and also by electron spin resonance in acetonitrile in the presence of a spin-trap (nitrone) [41]. At the modified surface, cyclic voltammetry shows attenuated response for the [Fe(CN) 6 ] 3−∕4− redox couple, compared to that at the unmodified surface, and is usually used as a quick test to verify the success of modification.…”