Inhibitors continued range

Chlorination of Methane. Methane can be chlorinated thermally, photochemicaHy, or catalyticaHy. Thermal chlorination, the most difficult method, may be carried out in the absence of light or catalysts. It is a free-radical chain reaction limited by the presence of oxygen and other free-radical inhibitors. The first step in the reaction is the thermal dissociation of the chlorine molecules for which the activation energy is about 84 kj/mol (20 kcal/mol), which is 33 kJ (8 kcal) higher than for catalytic chlorination. This dissociation occurs sufficiendy rapidly in the 400 to 500°C temperature range. The chlorine atoms react with methane to form hydrogen chloride and a methyl radical. The methyl radical in turn reacts with a chlorine molecule to form methyl chloride and another chlorine atom that can continue the reaction. The methane raw material may be natural gas, coke oven gas, or gas from petroleum refining. 

Substituted derivatives of 3-amino-5-phenyl-l,4-benzodiazepin-2-one continue to be a rich source of compounds that display a diverse range of biological properties. The 2-fluorophenylurea 166 is an inhibitor of respiratory syncytial virus (RSV) that appears to act by inhibiting the nucleocapsid (N) protein <2006JME2311, 2007JME1685>. This compound is the first orally active inhibitor of RSV to be advanced into clinical studies. 

Fig. 1. Polarization curve of metals with active, passive and (a) transpassive potential range including oxygen evolution (b) passive potential range going directly to oxygen evolution (c) continuing passivity for valve metals to very positive potentials. Pitting between critical pitting lim and inhibition potential fsj in the presence of aggressive anions and inhibitors.

There followed a very important series of papers coocenung the emulsifier-free system (Machi et al., 1978, I9 9a-d)- The equipment used was a modification of that used eailier, but the tetrafluoroethylene pressure was continuously recorded with the use of a strain gauge. In the first paper of the series (Machi er cl., 1978) the rate of polymerization was shown to be proportional to the 1.0 and 1.3 powers of the dose rate and the initial pressure, respectively. The activation energies were 0.8 above and —5.2 kcal/mol below 70°C. There was a maximum in the molecular weights at about the same temperature. This behavior is reminiscent of the behavior of ethylene and was again attributed to the increased mobility of the growing chains above the maximum temperature. The very low mobility would also account for the first-order dependence of the rate on the dose rate below 70 C. As before, n-hexadecane proved to be an excellent inhibitor of polymerization in the gas phase. Particle sizes in the range of 0.1-0.2 microns were obtained. 

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