Stable aminoxyls and an iminoxyl were observed by spin trapping and EPR techniques during the nitrationof coumarins containing a hydroxy group by nitric oxide. The trapped free radicals are deduced to be the resonance stabilized phenoxy-like radicals. The mechanisms for the nitrations are suggested.

Electron transfer reactions take place readily between 2,2,6,6-tetramethylpiperidine oxoammonium ions (1a, 1b) and phenothiazines (2a--2g), giving corresponding nitroxides (3a, 3b) and phenothiazme radical eations (4a--4g). The rate constants for the electron self-exchange reactions between 1 and 3, as well as between 2 and 4, are determined by EPR and IH NMR line-broadening effect in acetonitrile. Fay application of the Marcus theory, the kinetics of the cross-exchange reactions between 1 and 2 is studied.

Nitric oxide (NO) is an endogenous compound of the body involved in a variety of biological processes,1 including immunity-regulating functions, physiological control of blood pressure, and neurotransmission. Authentic NO in vivo has only a 0.1 s half-life.2 Nitrosothiols (RSNO), which are formed in vivo from the reaction of NO with protein or nonprotein thiols, can increase the effective tissue half-life of NO.3 RSNO is commonly referred to as a NO-donor and is found in various biological systems, such as in human plasma, airways, white blood cells, and rat cerebellum.4 Nitrosoglutathione (GSNO) has been shown to be one of the most aboundant RSNOs,4c,5,6 e.g., 0.3μM in bronchial lavage fluid and 0.7μM in brain, and to exhibit depressor action.7

The reaction of ketone arylhydrazone (1) with nitric oxide affords C1'-nitro azo-compounds (2) in good yields. Products were identified by NMR, IR, MS, and X-ray crystallography. The reaction is assumed to be most likely initiated by an electrophilic addition of NO2 to the carbon atom of the carbon-nitrogen double bond.

Using laser photolysis of basic anaerobic aqueous solutions of a-glycine, L-a-alanine and a-aminoisobutyric acid containing anthraquinone-2,6-disulfonic acid the two spin-polarized (CIDEP) C