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.