Contrasting responses in aqueous trifluoroethanol and aqueous ethanol as a probe for nucleophilic solvent assistance in solvolysis

Raber, Douglas J.; Neal, William C.; Dukes, Michael D.; Harris, J. Milton; Mount, Dwight L.

doi:10.1021/ja00494a020

Cited by 46 publications

(10 citation statements)

References 5 publications

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“…Finally, kinetic solvent isotope effect (KSIE) have been performed satisfactorily as an additional tool for mechanistic identification in solvolyses under favor of the values of solvolysis rate ratio 40%(v/v) ethanol-water and 97%(w/w) TFE-water solvent system [k 40E /k 97T ] Y , so that these values observed and the additional kinetic data were ascribed together in Table 4. For 1 4 and 2 4 , the values (≥ 1.49) for KSIE are within the range predicted for the bimolecular solvolysis which is accompanied by general base catalysis and [k 40E /k 97T ] Y values of < 215-254 are also within the range of favoring nucleophilic solvation, even if these values are less than 500 of corresponding methyl tosylate (MeOTs) 18 at 25 o C known as model compound for the bimolecular reaction. These results (l = 1.02-1.03) 4 are closely consistent with those previously analyzed in terms of dual Grunwald-Winstein parameters [equation (2)].…”

supporting

confidence: 61%

Correlation of the Rate of Solvolysis of 2-Chloro-thioacetophenones

Ryu¹,

Shin²,

Lim³

et al. 2004

Bulletin of the Korean Chemical Society

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According to the recent results of Kevill et al. 1-3 from kinetic data for solvolyses, they reported that the introduction of S-atom adjacent to a reaction center caused a partial shift away from the addition-elimination (AdE) through dual reaction channel (DC) to the ionization channel (IC) for solvolysis of acid chloride [ie: PhOCOCl 1 (AdE) → PhSCOCl 1b,2 ≈ PhOCSCl 3 (DC) → PhSCSCl 3 (IC)]. And more recent results of Ryu et al. 4 the results of the rates of solvolysis of α-methylthioacetyl chloride (1) and phenylthioacetyl chloride (2) in more than 33 aqueous solvent system including 2,2,2-trifluoroethanol (TFE)-ethanol (EtOH) solvent can be explained by the same mechanism with the same structure of transition state (TS), controlled by the contribution from strong nucleophilic participation (third order reaction model for TFE-EtOH system) 5 by the molecule of solvent as well as weakly solvent polarity (ionization), regardless of the different neighboring groups containing an S-atom [even if these are far away the reaction center, (C=O)] Results and Discussion Accordingly, we have conducted the further research to investigate how S-methyl and S-phenyl groups influence the reaction center as well as the variation of reaction mechanism in solvolysis of 2-chloro-2-methylthioacetophenone (3) 6 and 2-chloro-2-phenylthioacetophenone (4) 7 (not acid chlorides), respectively at 25 o C and 50 o C, for more than 40 solvent mixtures containing hexafluoro-iso-propanol (HFIP)water system and TFE-EtOH system (kinetic data in Table 1 and 2), by using the same regression analysis such as those

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supporting

confidence: 61%

Correlation of the Rate of Solvolysis of 2-Chloro-thioacetophenones

Ryu¹,

Shin²,

Lim³

et al. 2004

Bulletin of the Korean Chemical Society

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“…12, 13 Since earlier work, 7-11 considerable progress has been made by investigating the rates of solvolyses in alcohol-water mixtures: e.g. studies of trifluoroethanol-water mixtures have led to a better understanding of the role of the solvent as a nucleophile in heterolytic reactions, 14 and linear free-energy relation-ships have been expanded to include the effects of solvent nucleophilicity. 15 Also, solvent isotope effects in methanol have been used to assess the role of solvent as a general base catalyst.…”

mentioning

confidence: 99%

Chlorophosphate solvolyses. Evaluation of third-order rate laws and rate–product correlations for diphenyl phosphorochloridate in aqueous alcohols †

Bentley¹,

Ebdon²,

Llewellyn³

et al. 1997

J. Chem. Soc., Dalton Trans.

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“…Raber-Harris plots for 2n and 2t (see ESI †) show a clear difference in mechanism for these systems; 2n is not dependent upon solvent nucleophilicity (as would be expected for extensive participation) whereas 2t exhibits nucleophilic solvent assistance. 23 In contrast, Raber-Harris plots of 2u and 2v are very similar, showing very little if any nucleophilic solvent assistance for either system, as might be expected during formation of a benzylic cation (see ESI †).…”

Section: Kinetic Results and Discussionmentioning

confidence: 89%