| Abstract: | The oxidation of 12 aromatic compounds using either high voltage or radio frequency glow discharges has been studied. The reactions have been carried out by making the oxygen plasma reach the low vapor pressure substrate. This (1.5-3 ml) was placed into a double-walled glass vessel that was cooled down to temperatures close to its freeing point. Oxygen pressure was of the order of 0.05-0.30 torr, the ratio p(Oa) / (vapor pressure of the liquid) being in the range 10–120. The results obtained in the plasma-liquid interactions of this work considerably differ from those in the homogeneous gas phase. Neither fragmentation products in the traps nor polymers on the reactor walls have been detected. Product formation has proved to be more selective as well. For anisole and five monoalkylben:enes o-, m-, and p-alkvlphenols amounted to 65–86% of the total yield, ortho derivatives being the most important products. The oxidation of the alkyl side chain was observed at a lower level than the aromatic hydroxylation. No ipso substitution was detected. Diand trimethylbenzenes were also studied, di- and trirnethylphenols being the major products. For all substrates dihydroxy derivatives were the most important byproducts. Total conversion, i.e., mass transformed against initial mass of substrate, has been studied as a Junction of temperature of the liquid and oxygen fog, rate in the reactor, this ranging from 10 to 20 mMol/h. The optimum conversions were 7 to 40%. A correlation between these results and the behavior of the O(3P) population in the discharge has been /bund. |
