ISSN:
0538-8066
Keywords:
Chemistry
;
Physical Chemistry
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
Notes:
A combined flash photolysis and pulse radiolysis experiment was carried out to produce triplet pyrene (P) molecules in micelles of cetyltrimethylammonium bromide and Br2- in the surrounding aqueous medium. The reaction 3Pmic + Br2aq- → Pmic+ + 2 Br- was followed by optical absorption measurements in the 10-8-10-4-sec range. This reaction possesses a “fast” and a “slow” component with respective rate constants of 2.3 × 106 sec-1 and 1 × 109M-1 · sec-1.The fast component is related to the probability of a Br2- radical meeting a triplet pyrene containing micelle on the first encounter (only 16% of the micelles contained a triplet molecule). Reactions involving more than one Br2- radical-micelle encounter are ascribed to the slow component. The presence of two components reflects the fact that the residence time of a Br2- radical in the vicinity of a cationic micelle is substantially longer than the diffusion time of the radical between micelles. Thus the conditions met in micellar chemistry differ dramatically from those in ordinary solution kinetics where the encounter time is generally much shorter than the time between encounters. Some considerations on the energetics of this electron transfer reaction are also presented.
Additional Material:
2 Ill.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/kin.550080604
