Rate of Reaction of 1 and P(p-tol),. The following procedure is representative. A 5-mm NMR tube-was charged with 1 (16.0 mg, 0.028 mmol) and P(p-tol)p (170.0 mg, 0.559 mmol) and capped with a septum. A N, atmosphere was established, and C6D6 (0.7 mL) was added. The tube was transferred to a NMR probe, and rate data were acquired as described above. The concentrations of 1 and 4 were assayed by integration of the N M R resonances (17.2 and 14.4 ppm, 39 "C). The data are presented in Table 11.Rate of Reaction of (RRRR)-2a and P@-tol),. The following procedure is representative. A 5-mm N M R tube was charged with (RRRR)-2a (16.3 mg, 0.023 mmol), P@-tol), (72.0 mg, 0.239 mmol), and C6D6 (0.7 mL) in a manner analogous to the preceding experiment. The tube was transferred to a N M R probe, and rate data were acquired as described above. Concentrations of (RRRR)-Za and ( R R R R ) / (SRRR)-(~5-C5H5)Re(NO)(P@-tol)3)(OC,oHl,) (Sa) were assayed by integration of the ,'P N M R resonances (17.2, 13.2, and 14.2 ppm, 29 "C).Abstract: The effects of neutral, ionic, and zwitterionic micelles on the rate of the spontaneous decomposition of m-nitrophenyl 9-fluorenecarboxylate (I) were determined. Neutral micelles of a poly(oxyethy1ene) detergent produce a small increase in the decomposition rate. Negatively charged micelles of sodium dodecyl sulfate catalyze the reaction 2-fold while positively charged micelles of hexadecyltrimethylammonium bromide (CTAB) inhibit by a similar factor. Micelles of N-hexadecyl-N,N-dimethylammonium 3-propanesulfonate inhibit the decomposition of I to a larger extent than those of O-hexadecylphosphorylcholine while lysolecithin micelles do not affect the reaction rate. Thus, charge orientation of the monomer does not determine the kinetic effects of zwitterionic micelles on the rate of decomposition of I. The rate modifications produced by micelles on this reaction are consistent with electrostatic effects on the relative energies of initial and transition states. IntroductionMicellar incorporation of a substrate decomposing spontaneously can produce major effects in the reaction rate.' For different reactions distinct features of the micellar interface have been singled out as determining the observed effect. These include (a) conformer stabilization,* (b) decrease of hydration of the nucleophile,' (c) medium effects related to local polarity? and (d) specific interactions of ionic head groups with transition states.sThe consideration of micelles as a separate pseudophase has greatly facilitated mechanistic descriptions and quantitative rate analysis of chemical reactions in micelles.' However, the micellar reaction site is not a continuous phase.' Reactions of hydrophilic (and relatively hydrophobic) substrates occur in the micellewater interface.' At this site the effective polarity may differ significantly from that in the bulk solvent, and the local electrostatic field in both ionic and zwitterionic micelles may be It

Key indicatorsSingle-crystal X-ray study T = 293 K Mean '(C±C) = 0.004 A Ê R factor = 0.025 wR factor = 0.071 Data-to-parameter ratio = 13.3For details of how these key indicators were automatically derived from the article, see http://journals.iucr.org/e. # 2003 International Union of Crystallography Printed in Great Britain ± all rights reservedIn the mononuclear title complex, [Zn(PMG) 2 ]Á2H 2 O or [Zn(C 8 H 9 N 2 O 2 ) 2 ]Á2H 2 O, the Zn II center is surrounded by two N-(2-pyridylmethyl)glycinate (PMG) ligands, which impose a distorted octahedral environment on the metal. Two deprotonated molecules of the new tridentate N,N H ,O-donor ligand HPMG are facially coordinated to the Zn II center in such a way that the atoms of the same kind are mutually trans to each other, generating a centrosymmetric structure.

The alkaline hydrolysis of nine para‐substituted phenyl esters of para‐substituted benzoates was studied in the presence and absence of hexadecyltrimethylammonium bromide (CTAB) micelles. The second‐order rate constant for alkaline hydrolysis in CTAB micelles (K2m) was calculated using a pseudo‐phase ion‐exchange model. the substituent effect on the second‐order rate constant in the aqueous phase (k2w) and on k2m was analysed using Hammett's σ ρ plots. The calculated ρ values in micelles were 0.8 unit. larger than those in water. The effective low dielectric constant in the micellar surface may be responsible for the general effect of increasing the sensitivity of reactions to the electronic effect of substituents in micelles.

The kinetics and mechanism of the base-catalyzed oxidative cleavage of l,l-bis(p-chlorophenyI)-2,2,2-trichloroethanol (la) and l,l-diphenyl-2,2,2-trichloroethanol (lb) have been studied as a function of base concentration, solvent, and temperature. The pseudo-first-order rate constant for the disappearance of both la and lb increases

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