Photoredox Reaction of Methylene Blue and Lactose inAlcoholic Buffered Solution

Photoredox reaction of methylene blue (mb) and lactose (rh) in alcoholic buffered solution was studied on an optical processor with high beam of radiation of 661 nm, obtained through red filter via source of high power hg lamp. then absorption of photon of light mb get excited into mbt* and entered in reaction where color loss take place by the formation of two species of mb i-e semi reduced mb and lmb by following reaction: 2mb +hv(rightwards arrow)mb* + lmb the redox reaction was studied at different parameters like concentration of dye, lactose, acidity and temperature. the acidity of reaction mixture was adjusted by taking acid and base using hammett acidity function ho. the lactose dosage and uv power affect the color removal in a positive way. however any increase in dye concentration decreases the de-coloration rate. the ir spectra of isolated product showed the intensity band at 1729.7 cm1, indicating the presences of carbonyl group, which may be due to the association of sugar molecule with dye molecule. this may be regarded as an activated complex between mb and lactose which later dissociate into lmb and respective aldonic acid. the extent of photo bleaching was checked at elevated temperatures. a linear correlation in quantum yield (theta) between color loss and temperature showed that reduction of mb directly depend upon the temperature. a probable mechanism for the formation of leuco dye, consistent with above investigation has been proposed.