ContentsJuliars Dust completed his B.Sc.(Hons) in 1978 at the University of Waterloo, in southwestern Ontario, but then traveled east to Mt. Allison University, where he studied free radical chemistry of stericaliy-hindered aromatics with Professor Ross Barclay. In 1982 he traveled farther east to Dalhousie University where, under the guidance of Professor Don Arnold, he received a M.Sc. for a thesis that defined the «*n substituent scale for benzylic radicals. Changing direction, Dust moved west to Queen's University, and as a student of Professor Erwin Buncel, commenced a study of Meisenheimer complexes, including those formed by novel ambident polynitroheteroaromatics (i.e. super-electrophiles). This research led to a Ph.D. in 1987 and it continues to be a focus ot his effort. His postdoctoral work at University of Alabama in Huntsville with Professor Milton Harris sparked another continuing interest: preparation, application, and mechanistic investigation ot polyethylene glycol) derivatives. In 1989 he settled in Corner Brook, the western-mosl city in the eastern-most province in Canada, Newfoundland. There he accepted an Assistant Professorship at Sir Wilfred Grenfell College (Memorial University); he was granted tenure in 1994 and was promoted lo the rank of Associate Professor in 1995.

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A kinetic study is reported for nucleophilic substitution reactions of 2,4-dinitro-1-fluorobenzene (DNFB) with a series of secondary amines in MeCN and H2O at 25.0 degrees C. The reaction in MeCN results in an upward curvature in the plot of k(obsd) vs [amine], indicating that the reaction proceeds through a rate-limiting proton transfer (RLPT) mechanism. On the contrary, the corresponding plot for the reaction in H2O is linear, implying that general base catalysis is absent. The ratios of the microscopic rate constants for the reactions in MeCN are consistent with the proposed mechanism, e.g., the facts that k2/k(-1) < 1 and k3/k2 > 10(2) suggest that formation of a Meisenheimer complex occurs before the rate-limiting step and the deprotonation by a second amine molecule becomes dominant when [amine] > 0.01 M, respectively. The Brønsted-type plots for k1k2/k(-1) and k1k3/k(-1) are linear with betanuc values of 0.82 and 0.84, respectively, which supports the proposed mechanism. The Brønsted-type plot for the reactions in H2O is also linear with betanuc = 0.52 which has been interpreted to indicate that the reaction proceeds through rate-limiting formation of a Meisenheimer complex. DNFB is more reactive toward secondary amines in MeCN than in H2O. The enhanced basicity of amines as well as the increased stability of the intermediate whose charges are delocalized through resonance are responsible for the enhanced reactivity in the aprotic solvent.

31P NMR and UV-vis spectrometric evidence has revealed an unexpected regioselectivity in the reaction of fenitrothion, 1, an organophosphorus pesticide, with the cetyltrimethylammonium (CTA) surfactants CTAOH and CTAMINA, that incorporate the reactive counterions OH- and MINA- (the anti-pyruvaldehyde 1-oximate anion). While both micellar solutions accelerate decomposition of 1 compared to aqueous OH- alone, CTAMINA produced the largest rate enhancement (ca. 10(5)) at a pH (8.39) appropriate for environmental applications. In the absence of surfactant, reaction proceeds solely via the SN2(P) pathway. In the presence of surfactant but below the critical micelle concentration (cmc), a competitive SN2(C) pathway was observed in addition to SN2(P). Above the cmc, however, the CTAOH reaction again proceeded solely via the SN2(P) pathway while both pathways were operative with CTAMINA. The changes in reactivity and mechanistic pathway are discussed in terms of premicellar and micellar influences on rates and regioselectivity. A proposal that would account for the observed regioselectivity in the micellar system is that the aromatic ring and aliphatic side-chains of 1 are oriented toward the micellar interior, while the P=S moiety faces the aqueous pseudophase.