Catalyst inhibitors, detection

Detection of Catalysts and Inhibitors Ions, Amino Acids, Neurotransmitters, and Heme Proteins... 

Hydrazine compounds are widely used as fuels, corrosion inhibitors, catalysts, and dyes. However, such compounds are recognized as toxic agents consequently, their detection and processing are of much concern. Only a few recent papers pertain to the catalytic oxidation of hydrazine [148-150], with special emphasis... 

When 2 equiv (relative to catalyst) of 2,6-di-terf-butylhydroxytoluene (BHT, a radical reaction inhibitor) was added to the reaction, the yield of the reaction decreased by half. A radical trap experiment using cyclohexane was carried out in CCI4 as well, and together with 40% amination product, 12% of chlorocyclohexane was also detected. This result also suggests that a radical pathway is operative. When a 1 2.3 mixture of cis- and trans-2 pentene was reacted with PhI=NTs (Scheme 6.7), a 1 1.5 cis trans aziridine product was isolated, which suggests the mechanism may... 

Activators and inhibitors can be determined kinet-ically with good sensitivity and acceptable detection limits (between 10 and 10 mol 1 ), though not so good as those achieved in the determination of the catalyst. The precision, however, is rather poor in many instances. Similarly, inhibitory effects allow the kinetic determination of some substances that act as inhibitors for catalyzed reactions, provided the rate of the modified reaction is proportional to the inhibitor concentration. 

Moreover, selectivity could be also enhaneed if a specific interaction between the immobilized catalyst and the substrate in solution were to occur. A significant example is that of the voltam-metric detection of NO in the rat brain from a carbon fiber microelectrode modified with a [(H20)Fe PWii039] -containing poly(N-methylpyrrole) film and a Nation outer layer [150]. The good selectivity of this sensor was attributed not only to the Nafion membrane, which constituted an efficient electrostatic barrier against anionic interferents, but also to the formation of a metal-nitrosyl complex between the heteropolyanion and NO. The in vivo NO measurements were validated by injecting the rat with an NO-synthase inhibitor, which led gradually to the disappearance of the NO oxidation peak (Fig. 7). 

Once the principle that breaks down a reaction into elementaiy steps is accepted, it is clear that apart from the reactants - such as catalysts and inhibitors - and the products eventually formed, new species are involved in these elementaiy steps, as shown by the examples we have given. These species are probably particularly reactive because we can only rarely detect and identify them. 

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