Ultrasonic Acceleration of Redox Reactions

Studies on the homogeneous system had previously shown that the acid was the predominant product if the concentration of the reagents was low, or the partial pressure of oxygen was high [231]. These conditions are satisfied if one assumes that the involatility of potassium hydroxide leads to an extremely low concentration of base in the vapour phase, that is, at the site at which reaction occurs. 

Similar results were later obtained by Han and co-workers using BaMn04 and KMn04 CUSO4 5 H2O [233]. 

Aromatic nitro-groups can be reduced to give the equivalent aniline 

The conversion yield for this process is reported to be directly proportional to the amount of activated carbon employed [234], 

Petrier and Luche have reported preliminary results from a study of the reductive properties of an aqueous Zn—NiCl2 (9 1) system [235]. Selective reduction of a,p-unsaturated carbonyl compounds was reported to occur in water/ethanol mixtures. Ultrasound increases the rate of the reaction, but its role is not simply that of an initiator as chemical activation of the zinc, using copper iodide or ammonium chloride, fails to effect reduction of the substrate. In addition, the authors stress that reaction does not occur in the absence of water. Reduction occurs preferentially at the double bond of the enone and is virtually complete before reduction of the carbonyl group begins. This degree of selectivity is not observed in the case of a,p-unsaturated aldehydes. 

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Ultrasonic Acceleration of Redox Reactions UAIH4, hexane,... 

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