Grunwald-Winstein effect

The Hammett equation is not the only LFER." ° Some, like the Hammett equation, correlate structural changes in reactants, but the Grunwald-Winstein relationship (see p. 452) correlates changes in solvent and the Brpnsted relation (see p. 337) relates acidity to catalysis. The Taft equation is a structure-reactivity equation that correlates only field effects. ... 

Ruasse and Dubois (1984). Rate data for styrenes and a-Me-styrenes (from Durand et al., 1966) and for methoxy- and hydroxystyrenes (from Loudon and Berke, 1974). "Values in parentheses are for bromination in water (Ruasse and Lefebvre, unpublished results). Grunwald-Winstein coefficients for solvent effects. Values in parentheses are for protonation in MeOH (Toullec, 1979 Dubois et al., 1981b). Bronsted exponents. 

Studies of medium effects on hexacyanoferrate(II) reductions have included those of dioxygen,iodate, peroxodisulfate, - [Co(NH3)5(DMSO)] +, and [Co(en)2Br2]+. Rate constants for reaction with dioxygen depended strongly on the electron-donor properties of the organic cosolvent. Rate constants for reduction of peroxodisulfate in several binary aqueous media were analyzed into their ion association and subsequent electron transfer components. Rate constants for reduction of [Co(en)2Br2] in methanol water and dioxan water mixtures were analyzed by a variety of correlatory equations (dielectric constant Grunwald-Winstein Swain Kamlet-Taft). 

The application of correlation analysis of solvent effects to mechanistic studies of solvolysis has been reviewed by Takeuchi in Japanese.110 The article mainly covers die behaviour of tertiary chloro compounds. Tins author s research group has continued experimental studies in this area.111-113 Rates of solvolysis of 2-chloro-2,4-trimethylpentane have been measured in 17 solvents and analysed through the extended Grunwald-Winstein equation, which includes a term for nucleophilic participation.111... 

Application of the extended Grunwald-Winstein equation to solvolyses of propyl chloroformate, PrOCOCl, in a variety of pure and binary solvents indicated an addition-elimination pathway in the majority of the solvents but an ionization pathway in the solvents of highest ionizing power and lowest nucleophilicity. For methanolysis, a solvent deuterium isotope effect of 2.17 was compatible with the incorporation of general-base catalysis into the substitution process.21... 

First-order dependence is observed with respect to both the oxidant and reductant in the oxidation of substituted anilines with peroxomonosulfate anion. Addition of acid causes retardation of the reaction. Yukawa-Tsuno correlation of the rates gave a negative reaction constant (p -1.7) and analysis of the effect of solvent in terms of Grunwald-Winstein equation (m 0.4) indicated an S -type reaction. 

Oxidation of thio acids by tetrabutylammonium tribromide showed Michaelis-Menten-type kinetics with respect to the thio acid. The effect of solvent composition was analysed using the Grunwald-Winstein equation. A mechanism involving the formation of an intermediate complex in the pre-equilibrium and its subsequent decomposition in a slow step is proposed.129... 

Grunwald-Winstein eqn (9) with OTs values derived from 2-adamantyl tosylate (Section 3, p. 36) and with iV0Ts values based on methyl tosylate (Section 5), Schadt et al. (1976) have correlated a variety of solvolyses of other tosylates. Whilst their work is more extensive in that Sn 2 type solvolyses were studied (Table 9), only tosylates have been examined and solvation effects caused by different leaving groups are thus minimized. However, the subtlety of solvation effects is emphasized by the dependence of the relative rates of p-bromobenzenesulphonates and tosylates on solvent electro-... 

The initial objective of our work was to quantify solvent effects (particularly solvent nucleophilicity) by adapting the Grunwald-Winstein equation (2) (5). In equation 2, k is the rate of solvolysis of a substrate (RX) in any solvent relative to 80% v/v ethanol-water (k0) and Y is the solvent ionizing power defined by m = 1.000 for solvolyses of tert-butyl chloride at 25 °C. In this chapter, a discussion of equation 2 and similar free-energy relationships is presented. At the time our work began (1969), in collaboration with Schleyer, mechanisms of solvolytic reactions were close to a high in controversy (6-8). More recent mechanistic developments (9-13) are not reviewed in detail here, but increased recognition of the importance of nucleophilic solvent assistance should be noted. 

Rates of solvolysis of cinnamoyl chloride and its 4-chloro and 4-nitro derivatives were analysed using the simple and extended Grunwald-Winstein equations. Studies of solvent effects in the solvolysis of isopropenyl, isobutyl,and propargyl chloroformate " and of 1- and 2-naphthyl chloroformate were reported. 

Kinetic studies of the solvolysis of phenylmethanesulfonyl chloride (PhCH2S02Cl) in a wide range of solvent mixtures at 308 K were reported. Since an extended Grunwald-Winstein plot was linear and a kinetic solvent isotope effect of 2.34 was seen for MeOH/MeOD, a dissociative S 2 mechanism was indicated. ... 

The cr-substituent effects and solvent effects (extended Grunwald-Winstein equation) for solvolyses of / -X-substituted benzoyl chlorides (X = OMe, Me, H, and Cl) in 97% wt/wt hexafluoroisopropanol/water was explained by two competing pathways. Plots of log k versus a were consistent with a cationic path and explained by an 5 n2-5n1 spectrum of mechanism. Electron-donating groups favoured the reaction and values of p increased in the order AcOH < HCO2H < TEE < HFIP. A benzoyl cation intermediate was trapped in hexafluoroisopropanol. Ab initio calculations of heterolytic bond dissociation energies of various chloro- and fluoro-substituted and other benzoyl chlorides were correlated with log k for solvolyses... 

MeO , OH , or EtO and methyl fluoride, anisole, and 4-fluoroanisole on the gas-phase 5 2 reactions between dimethylmethylphosphonate and methylformate and HOO versus HO , MeO , or EtO in an attempt to discover the origin of the O -effect on the Sf 2 reaction of carbanions with 4-substituted benzyl chlorides in liquid ammonia " on the solvolysis reaction and the 2 reaction between phenoxide ions, and both neutral and negatively charged amines and 4-substituted benzyl chlorides in liquid ammonia on the ionization rates (the step) of the 5" 1 reactions of many substituted trityl halides and carboxylates in aqueous acetone and in aqueous and pure acetonitrile in the presence of piperidine on the ionization rates ( i) of the 5 reactions of various diarylmethyl chlorides in the presence of piperidine, pyridine, or PPh3 in several dipolar aprotic solvents on the solvolyses of X,Y-substituted benzhydryl acetates in various aqueous MeOH and EtOH solutions and on the dispersions observed in Grunwald-Winstein correlations of 5 solvolyses of substrates with substituents containing adjacent tt-electrons. ... 

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