Reaction of di‐tert‐butylnitroxide radicals

Abstract

Di-tert-hutylnitroxide (DTBN) is the simplest of the stable nitroxide radicals and is only consumed a t temperatures higher than 9OoC or in the presence of very reactive substrates. The pyrolysis of DTBN in solution gives, at least at low conversion, 2-methyl-2-nitrosopropane and di-tert-hutylnitroxide-tert-hutyl ether. The reaction involves, as the rate-limiting step, the cleavage of the C-N bond. This reaction takes place with an activation energy of 33 kcal/mol. DTBN is stable in the presence of styrene, aldehydes, hydrogen peroxide, wmethyl-N-ethyl nitrone, phenol, and triphenylmethane. On the other hand, it reacts readily with diethylhydroxylamine, ascorbid acid, ethanethiol, and hexanethiol. For the two former compounds the reaction involves a hydrogen transfer as the rate-determining step, and the reaction proceeds, a low conversion, with simple second-order kinetics. The reaction with the thiols is complex and shows a clear induction time.

Redox: Organic Robust Radicals and Their Polymers for Energy Conversion/Storage Devices

“…Although cyclic structures can be key to the robustness of nitroxides, some acyclic compounds also exhibit bistable redox reactions (Table ). One of the simplest nitroxides, di- tert -butylnitroxide (Scheme ), is stable at 90 °C and in ordinary solvents, although its oxidized state quickly decomposes . The redox reversibility of acyclic nitroxides neighboring only alkyl groups has been insufficient (e.g., tert -butyl, NO98 and NO99 ) …”

Nitroxide-catalyzed transition-metal-free aerobic oxidation processes

“…24 On the other hand, the less rigidified DTBN exhibits decreased stability along with a higher cost. 25 Due to the low OH-bond dissociation energy (BDE) of TEMPOH (289 kJ mol −1 ), 26 the thermodynamic driving force for direct oxidation via H-abstraction by TEMPO or related dialkyl nitroxides is low in most cases and CH-activation using this route can only be achieved at activated positions. Notably, the reverse process (TEMPOH to TEMPO) is highly efficient in basic media under an aerobic atmosphere.…”

Radical intermediates and antioxidant activity of ascorbic acid

“…19 20 21 22 There have been a number of kinetic studies on the reduction of nitroxides by ascorbic acid carried out in aqueous solution [64][65][66][67], in micelles [64], in natural biomembranes [7,60] and in fl-cyclodextrin [68][69][70]. The common feature of these studies involves the determination of the pseudo-first order rate constants for the decay of the nitroxides by ESR in the presence of a large excess of ascorbic acid.…”