Aliphatic semidiones. XXV. Bicyclo[n.2.1]alkane-2,3-semidiones

Abstract

7237(27) This type of mechanism was also suggested by Romans, et al.,2 for the oxidation of tetramethylhydrazine with iodine.

Electron spin relaxation in polarized secondary radicals

“…A much fuller study was possible when camphorquinone was used as substrate for this gave strong polarized signals in a variety of solvents ; the spectrum observed in 2-octanol is shown in figure 1. Previous studies of this spectrum in other solvents [8][9][10] have suggested that the radical concerned is the neutral species with the one hydroxyl proton produced by hydrogen abstraction from the solvent exchanging too rapidly between the carbonyl oxygens for its coupling to be observed. Simulation of the spectrum using the literature values for the Downloaded by [Purdue University] at 03:56 12 April 2015 coupling constants yields a close but not precise fit to our (or the literature) spectrum and the identity of the radical remains in some doubt.…”

Radical anions and cations derived from enedithiols, hydroxy-enethiols, and saturated dithiols

“…These numbering patterns are used only when referring to radical anions and cations, and in naming the precursors to the radicals, normal numbering procedure will be used. by hydrogen in the 7-anti position (1,2). A mechanism involving homohyperconjugation can be invoked to explain the large splitting.…”

“…Structures ^ and illustrate how spin may be transferred to by homohyperconjugation (2). This mechanism can operate only when 0 1 0 the HOMO of the spin-label is symmetric with respect to the plane bi secting the spin-label and containing H^^.…”

“…These splittings are due to spin polarization, a mechanism which does not depend on the symmetry of the spin-label. A spin-polarized structure such as 9^ can account for the small splitting by when spin cannot be transferred via homohyperconjugation (2). The radical cations corresponding to the anions 1., and 4-8…”

“…Had the ESR spectrum for semidithione been more highly resolved, observed splitting constants of a^ = (3.01 G)(0.55) = 1.7 G and a^ = (2.08 G)(0.55) = 1.1 G would have been expected for the exo and bridgehead hydrogens, respectively. The ratio a^(20)/a^(l) is larger for than for the exo H 1/2 1/2 2 and bridgehead hydrogens, a is a function of [(p ) + (p_ ) ] , /a ^2 1^3where the sum is used when, for the HOMO, the coefficients of the atomic orbitals at C2 and Cg are of like sign and the difference is used when the coefficients are of opposite sign(2). Because this relationship is not a linear one with respect to p, different a^ ratios are observed for H^^ and or…”