Nitrosation, mechanisms

Figure L H-Nitrosation mechanisms known in 1961, according to Ridd ( 6),...

Neighbouring group participation by carbonyl groups in ester hydrolysis, 28, 171 Nitration, nitrosation, and halogenation, diffusion control and pre-association in, 16, 1 Nitrosation, mechanisms, 19, 381... 

In the oxidative aromatic substitution of benzene with the nitrosonium cation (NO+), the benzene complex with symmetry 12 has been calculated as a local minimum at the B3LYP/6-31G(d) level of theory with an energy of 48 kcal mol-1 above that of the 7t-complex 13 <1999PCA4261> therefore, the former should not be relevant for the nitrosation mechanism as was previously proposed (Figure 3) <1985RJOC842>. 

The author thanks Professor J. H. Ridd and Dr. G. Stedman for many helpful discussions of aspects of nitrosation mechanisms, which have, over some years, stimulated much interest in this area of chemistry. 

Many pathways exist to generate a nitrosothiol in vitro by the 1-electron oxidation of NO. Nitrosothiols can be formed via the reaction of a thiol with N2O3, a nitrosating agent that is an intermediate in the decomposition of NO in aerobic solution, or via the direct reaction of NO with a thiol to form an addition complex (SNO ) followed by a 1-electron oxidation. S-nitrosation of a protein thiol also can occur by a trans-S-nitrosation event from a low molecular weight nitrosothiol, such as S -nitrosoglutathione, or from a nitrosated protein cysteine (8). Whereas the in vivo mechanism of protein S -nitrosation is unknown, a protein-mediated trans-S -nitrosation mechanism is an attractive possibility because of the specificity it could impart on the reaction. Additionally, the same protein could catalyze both the nitrosation and denitrosation of a specific cysteine. A report showing that the protein thioredoxin can transnitrosate caspase-3 selectively and reversibly lends support to this proposal (34). 

Some comprehensive reviews of the chemistry of C-nitroso compounds already exist. Since the latest general review was published, no other relevant new findings on the formation of nitroso compounds by substitution processes have been reported. Reviews of special interest deal with the syndieses and properties of aliphatic fluoronitroso compounds, nitrosoalkenes and nitrosoalkynes, electrophilic C-ni-troso compounds, a-halonitroso compounds and nitrosation mechanisms. ... 

---