Photochemical Reactions between Methylene Blue and Tri-, Di- and Monomethylamine. I

The photobleaching of the evacuated aqueous solution of methylene blue by dint of tri-, di- or monomethylamine was studied. The reaction products were identified to be leuco dye and amine oxide, the former by a spectroscopic method and the latter by a chemical one. It was found that a long lived metastable intermediate is produced and this intermediate slowly returns to the original dye even in the dark. Furthermore it was found that this intermediate has its own absorption near infrared region. On the basis of the above observations, the following scheme was proposed for the reaction. (Remark: Graphics omitted.) in which the process IV can be neglected in the present experimental conditions. From the above scheme, ths following rate formula was derived which can represent all the experimental results satisfactorily. x=Ae^-(k+s)t+Be^-(k-s)t where x is the concentration of methylene blue.