水酸化カリウム存在下でのメタノールによるニトロソベンゼン還元反応の速度論的研究
1989 年 38 巻 9 号 p. 694-698
詳細
1989 年 38 巻 9 号 p. 694-698
The reduction of nitrosobenzene with methanol in the presence of potassium hydroxide was studied spectrophotometrically.
The reaction in the absence of potassium hydroxide was inhibited by galvinoxyl. It gave azoxybenzene and formaldehyde cleanly and its rate could be expressed as follows :
Rate=κ2CNSB2
The rate equation in the presence of potassium hydroxide was found to be :
Rate (KOH) = (κ2+κ3COH-/CH2O) CNSB2
The reaction had an induction period, and maximum conversion did not attain 100%. Besides azoxybenzene and formaldehyde, other products such as aniline, azobenzene, formic acid, and phenylhydroxylamine were detected in the latter reaction. Moreover, these by-products were formed even during the induction period. Both the percentages of main product loss and the induction period were proportional to the concentration of potassium hydroxide.
The reaction in the presence of potassium methoxide and in the absence of water had no induction period and formed the four by-products. The induction period and formation of the four by-products under alkaline condition may possibly have been due to hydroxide ion. Probable mechanisms for the radical reaction of azoxybenzene formation involving dimerization of phenylhydroxylamino radical, and for the ionic reaction of by-products formation initiated by hydroxide ion are presented and discussed.
