The thermocoloration of a water-soluble spiropyran, T,3',3'-trimethylspiro[2Ff-l-benzopyran-2,2'-indoline]-6-sulfonic acid (1), which has been newly synthesized in this work, in the anionic AOT reversed micelles has been investigated in order to evaluate the effect of the reversed micelles in controlling the reaction rates or pathways by restricting the mobility of the substrates being situated in a specific reaction field. The probe 1 showed a negative photochromism in polar solvents such as water, MeOH, and EtOH as well as in the AOT reversed micelles. The thermocoloration rates of 1 were retarded by about 20 times in the 0.2 M AOT/O.6 M H20/hexane micelles compared with those in MeOH in which microscopic polarity was comparable to that in the interior core of the reversed micelles adopted. This was explicable in terms of the restriction in the internal rotation of the 2,3 bond of 1 during the thermocoloration accompanied by the cis-trans isomerization in a largely restricted field as provided by the reversed micelles. The extent of deceleration in the thermocoloration in the AOT reversed Hydroboration Kinetics. 4. Kinetics and Mechanism of the Reaction of 9-Borabicyclo[3.3.1]nonane with Representative Haloalkenes.

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The association of nitroxide spin probes with aggregates of peptide-surfactants was investigated in aqueous media. The spin-labeled fatty acid was completely incorporated into the peptide-surfactants with anisotropic immobilization, while the less hydrophobic nitroxide radical was distributed between the hydrophobic and electrostatic regions of the aggregates. The peptide-surfactants may form tighter aggregates than the ordinary micelles.

In order to clarify micro-environmental effects on the reactivity of mercapto groups in enzymes, cationic surfactants bearing a mercapto group, N-hexadecyl-Nα-(3-trimethylammoniopropionyl)-l-cysteinamide bromide (CM·Cys-1) and N-dodecyl-Nα-(6-trimethylammoniohexanoyl)-l-cysteinamide bromide (CM·Cys-2), were synthesized and their kinetic behavior investigated. The surfactants above their critical micelle concentrations markedly catalyzed the decomposition p-nitrophenyl hexanoate (PNPH) and acetate (PNPA), the concentrationrate profiles being found to be those for typical micelle-catalyzed reactions. The rate constants for the degradation of PNPH as catalyzed by CM·Cys-1 and -2 in the micellar phase are 0.482 and 0.197 s−1, respectively, in 9.8% (v/v)ethanol–1.0%(v/v)dioxane–1.0%(v/v)methanol-water at 30.0±0.1 °C, pH 8.65, and μ0.10 (KCl). The difference in catalytic activity can be attributed partly to the micro-environmental effect on the pKa value of the mercapto group lying at the reaction center. The rate constants for the thiolate anions (true reactive species) of CM·Cys-1 and -2 to react with PNPH were identical with each other irrespective of the nature of the surfactants. The electrostatic effect provided by the cationic charge in the Stern layer, which acts to reduce the pKa value of the reactive mercapto group, seems to play a more important role than the desolvation effect on the thiolate anion by the hydrophobic field.

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