Étude par résonance paramagnétique électronique de la photolyse en phase liquide de composés nitrés

Comment on “Photochemical Activities of N‐Nitroso Carboxamides and Sulfoximides and Their Application to DNA Cleavage”

“…Thus, I suspected that the authors had in fact observed a nitroxide radical deriving from the solvent THF. This turned out to be the case because their EPR data are essentially identical to the values reported for the bis‐(α‐tetrahydrofuryl) nitroxide radical [5] …”

“…[3] Thus,Isuspected that the authors had in fact observed an itroxide radicald eriving from the solventT HF.T his turnedo ut to be the case because their EPR data are essentially identical to the values reported fort he bis-(a-tetrahydrofuryl) nitroxide radical. [5] Hydrogen atom abstraction from THF occurs preferably at the a-positions to oxygen. Quantumc hemical density func- tional theory (DFT) calculations on the CBS-QB3l evel predicted an a-CÀHb ond dissociation enthalpy (BDE) in THF of 92.2 kcal mol À1 ,i nf ull agreementw ith the experimentalv alue (92.0 kcal mol À1 [6] ).…”

Spin-labeled carbohydrates

“…30 The mono-and dioxygen compounds 33 nitrogen compound 35 by the reaction with 5. In the following structures (36)(37)(38)(39)(40)(41)(42)(43)(44)(45)(46)(47) the spin-labeled side chains are abbreviated as OS1 and NHS1. The reaction of thio sugar 30 with 1 or 0.5 equiv of 33 and 35 gave the monosubstituted (36,38) and disubstituted (37,39) products, respectively (Scheme VII).…”

Study of PhotoinducedN-Hydroxy-arylnitroxide Radicals (ArNO•OH) by Time-Resolved EPR

“…The DFT method of calculations was first validated on EPR spectra of radicals previously described in the literature. [12][13][14][15][16][17]25 2. Experimental Section TR-EPR Experiments.…”

“…However, it was not produced photochemically and is not, strictly speaking, an ArNO•OH radical. Several steady-state EPR studies of the photochemistry of aromatic nitro compounds were reported, but in most of them only the anion radical ArNO•O - or secondary radicals (ArNO•H, ArNO•R, and ArNO•OR) were observed. ,,− Only two ArNO•OH radicals have been reported by steady-state EPR studies: 2,3,5,6-(Cl) 4 −PhNO•OH , and 4-CN−PhNO•OH . Several authors have reported EPR spectra which they attributed to PhNO•OH , but were later discovered to be spectra of PhNO•OR radicals …”