| Abstract
| - Dediazoniation of o-methylbenzenediazonium tetrafluoroborate was investigated in SDS/BuOH/H2O(SDS = sodium dodecyl sulfate) reverse micelles, RMs, and, for comparison, in binary BuOH/H2O mixturesby employing a combination of spectrophotometric and chromatographic techniques. RMs were characterizedby steady-state fluorescence; the data indicate that the aggregation number of the RMs increase uponincreasing [SDS], while the radius of the water pool is mainly controlled by the amount of water in thesystem, and that the thickness of the interfacial region increases upon increasing the amount of BuOHin the system, in agreement with literature reports. Experimental evidence suggests that dediazoniationmainly takes place in the interfacial region of the RMs. Kinetic data show that a turnover from theheterolytic to the homolytic mechanism takes place about pH = 5; the variation of the observed rateconstants, kobs, with pH following an S-shaped curve. At pH ∼ 2, kobs values are insensitive to solventcomposition both in RMs and in the binary mixture; however, kobs values in RMs are slightly lower thanthose in BuOH/H2O, probably due to the presence of SDS. High-performance liquid chromatography analysesof the reaction mixture indicate, in both RMs and in binary mixtures, the main dediazoniation productsare the heterolytic ArOH and ArOBu, their yields depending on the composition of the system, and onlysmall (<10%) amounts of the reduction ArH product were detected. The data at low pH are interpretedin terms of a DN + AN dediazoniation mechanism, i.e., a rate-limiting formation of an extremely reactivearyl cation that further reacts with available nucleophiles in the solvation shell.
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