The reaction products and kinetics of the oxidation of several substituted toluenes by Co111 acetate in acetic acid solution were determined. Under anaerobic conditions the substituted toluenes were first converted into benzyl acetate and subsequently into benzaldehyde. Under anaerobic and aerobic conditions the same rate equation and rate constant were found for the oxidation, but the product distribution differed strongly. The main products of the aerobic oxidation are benzaldehyde and benzoic acid, derived from the substituted toluenes used. Regeneration of Co111 acetate occurs in aerobic solutions, which leads to stationary values for the concentration ratios Coni/Co" and RCHO/RCH3. A reaction mechanism is proposed to explain the results obtained.

6 G. Heijkoop et al. /Decomposition and disproportionation of hydrazyl radicals and hydrazo compoundsLes aldehydes et salicylates de methyle substitub sont tous des produits commerciaux utilisb aprts distillation ou recristallisation. de reaction est celui d'un melange equimoleculaire de benzaldehyde et d'acide salicylique, confirmant le fait que la saponification de. la fonction ester etait compltte. Mesures cinetiques A) Mkthodes cinktiques appliyukes aux acktals mkthoxycarbonyltsLa reaction d'hydrolyse de ces acetals aryles est suivie, par spectrophotometrie U.V., dans un milieu aqueux, tamponne, de force ionique p = 0,l et a une temperature maintenue B 25°C f 0,l par circulation d'eau dans des cuves a jaquette. Une etude spectrale de la solution cinetique en debut et en fin de reaction nous permet, pour chaque produit, de determiner la longueur d'onde optimale pour laquelle la variation de la densitt optique utilise la pleine tchelle de I'enregistreur. Une solution-mere d'acetal est prepark en solubilisant 5 pl de produit dans 5 a 10 ml d'ethanol absolu; 20 pI de cette solution sont ajoutes a I ml de tampon; la concentration en acetal de la solution obtenue est donc de l'ordre de 3 1 6 10-5M suivant les cas et permet d'observer une variation de la densite optique de 0,8 unitb environ au cours de la reaction. Le lissage de la courbe exponentielle obtenue est effectut sur ordinateur d'aprks la mtthode des moindres carrts et nous donne la valeur de kobq. B) Mkthodes cinktiques appliqukes aux acetals carboxylds (Ib-IXb)La reaction d'hydrolyse de ces acetals est suivie, comme pour leurs esters, dans un milieu aqueux, tamponne, de force ionique 0,l et a 25OC f 0,l. 20 pl de la solution-mere du sel de potassium de chaque acttal sont ajoutes a 1 ml de la solution tampon et la densitk optique du melange obtenu apres agitation est mesurke en fonction du temps.Le traitement des donntes cinttiques est similaire B celui indiqut dans le cas des acktals-esters. Abstract. The mechanisms of decomposition and disproportionation of hydrazyl radicals and hydrazo compounds, derived from azo dyes, have been studied by flash photolysis, flow experiments and fluorescence spectrometry. The hydrazyl radicals undergo a combined decomposition and oxidation process, resulting in the formation of amines and iminoquinones, and regeneration of part of the amount of dye used in their preparation. Hydram compounds are formed upon further photoreduction of hydrazyl radicals, and decompose in a similar fashion as the latter.

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Optical and ion migration experiments were carried out with acetic acid solutions of Co" and Co"' acetate. The results indicate a mononuclear structure with six ligands. The largest amount of these complexes is uncharged.

83In general, these experiments show the importance of the pretreatment of the CaA zeolites for the adsorption of CO. Moreover, one must be very careful in comparing CO adsorption results, because the quantity adsorbed depends largely on the pretreatment conditions of the CaA zeolite. Small changes in pretreatment can result in large adsorption J. A. Michelena acknowledges a grant from the EEC differences. Therefore, we suggest that for adsorption (European Economic Community). E. F. Vansant thanks measurements on CaA zeolites, always fresh CaA zeolite samples, dehydrated at identical temperatures for the same period of time, should be used. Abstract. ESR-spectra of hydrazyl and aminonaphthoxy radicals formed upon photoreduction of azo dyes have been measured. For the hydrazyl radicals the results obtained further confirm previous investigations of the mechanism of photoreduction of azo dyes. The direct identification in photoreduced dye solutions of aminonaphthoxy radicals, which are formed in the oxidation reduction equilibrium of aminonaphthols and iminoquinones provides strong evidence for previously proposed mechanisms for the disproportionation of hydrazyl radicals Acknowledgement