J. Phys. Chem. 1981, 85, 3456-3461
3456
kl[Chll] and the pigment oxidation proceeds only in this first step by the reaction of pigment molecules lying at the water-micelle interface. We obtain for this first step K [ChlT] = kl[Chll]. At the end of the reaction, Chll molecule contribution to the rate v becomes insignificant, and the reaction rate is equivalent to the v2 term: d[Chl+*]/dt = d[Chl,+.]/dt = It2[Ch12][X2-.,] For X2-. distribution between inner and outer micellar phases, thermodynamical equilibrium cannot be involved because X p mis rapidly consumed by step 2; consequently, we can introduce for X2-qma small although constant value according to the steady-state situation of the reactive mixture. d[Xz-*,]/dt = 0 d[X,--,]/dt = ke[X2-*aqIIX-mI - ItofdXPm][X-,,I - k2[X2-*,] [Chl,] We introduce a new kinetic constant distribution K' of X2-a:
K' = [X2-~mI/[X2-~,,1 with
K' = ke[X-ml/(kodX-aql + k2[Ch121) in this last case we have [X,-.,]
=
(X,- [Chl+*])K'/(l + K')
The theoretical expression is now In ( X , / ( X , - [Chi'.])) = k,'[Chl,]t with k,' = k2Kr/(1 + K') From the experimental pseudo-first-order constant k, we can determine the constant It;: k[ChlT] = k;[Ch12]. Then for v,
