Some magnetic resonance parameters for acyl nitroxides: A comment on nitroxide configuration.

Kinetic Study of the Phthalimide N-Oxyl (PINO) Radical in Acetic Acid. Hydrogen Abstraction from C−H Bonds and Evaluation of O−H Bond Dissociation Energy of N-Hydroxyphthalimide

“…Although one might expect the BDE of (PhCO)( t -Bu)NOH to be larger than that of (CF 3 ) 2 NOH, the actual BDE of PhCON( t -Bu)OH (323 kJ mol -1 ) is smaller than that of (CF 3 ) 2 NOH (346 kJ mol -1 ), which is reflected in the difference of the rate constants for hydrogen abstraction reactions from toluene. Jenkins et al measured the π-spin density on oxygen in 17 O-labeled (PhCO)( t -Bu)NO• and found that 12% of the π-spin exists on the carbonyl oxygen. , We are not sure how much π-spin exits on the carbonyl oxygen of the PINO radical. However, the two acyl groups of PINO• would delocalize the nitrogen lone pair to a greater extent than on the (PhCO)( t -Bu)NO•.…”

“…Jenkins et al measured the π-spin density on oxygen in 17 O-labeled (PhCO)-(t-Bu)NO• and found that 12% of the π-spin exists on the carbonyl oxygen. 38,40 We are not sure how much π-spin exits on the carbonyl oxygen of the PINO radical. However, the two acyl groups of PINO• would delocalize the nitrogen lone pair to a greater extent than on the (PhCO)(t-Bu)NO•.…”

Acyl nitroxides

“…(7a) (Tb) (7c) [13], which is greater than that found in dialkyl nitroxides, although some spin is found on carbonyl oxygen [14]. For purposes of comparison with the X-ray results, MNDO bond lengths are included in Figure 2; the calculations give a coplanar energy minimum with oxygen atoms "trans".…”