REACTION OF HYDRATED ELECTRONS WITH BILIRUBIN IN CTAB MICELLAR MEDIUM

Reaction of hydrated electron with Bilirubin (BR) has been studied in cetyltrimethyl ammonium bromide (CTAB) micellar medium using nanosecon d pulse radiolysis technique. Interactions of CTAB with BR have also b een studied in both micellar and premicellar regions monitoring the ch anges in absorption and fluorescence properties in these media. It has been observed that at a concentration of 3 x 10(-5) mol dm(-3) BR and 6.4 x 10(-5) mol dm(-3) CTAB a precipitation occurs which is attribut ed to the separation of a charge pair complex. However, at higher CTAB concentrations formation of its micelles takes place where the comple x breaks and free BR molecule gets incorporated in the Stern layer of CTAB micelles. The BR molecule experiences a dielectric constant of ab out 40 in the micellar environment. The binding constant for the micel lization of BR was computed to be 2.7 x 10(4) dm(3) mol(-1). As a resu lt of this incorporation, hydrated electron reaction with BR in the mi cellar medium becomes faster by a factor of about 4 as compared to tha t in homogeneous aqueous medium. The transient formed by the reaction of e(aq)(-) with BR gave an absorption band with red shift of about 25 nm in the CTAB micellar medium as compared to that in aqueous system. The transient decay is considerably slowed down in this micellar medi um indicating its incorporation in these micelles. The effect of chang ing the concentration of tertiary butanol on the rate constant for the reaction of e(aq)(-) with BR in homogeneous aqueous solution at pH 11 has also been studied.