Steric Effects on Reaction Rates. IV. Evaluation of the Ketone Model for the Solvolysis Transition State of Secondary <i>p</i>‐Toluenesulfonates

Müller, Paul; Blanc, Jacky; Pcrlberger, Jean‐Claude

doi:10.1002/hlca.19820650514

Cited by 11 publications

(1 citation statement)

References 45 publications

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“…The first attempt to rationalize rate constants of solvolysis of secondary derivatives used strain estimates for carbenium ions, based on IR-stretching frequencies of carbonyl groups and nonbonded interactions . These qualitative estimates were subsequently replaced by empirical force-field calculations which were particularly successful in the context of bridgehead solvolysis, but were also applied with various degrees of sophistication toward the solvolysis of secondary aliphatic derivatives . However, owing to the empirical nature of these methods, the significance of the results could not be truly assessed.…”

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confidence: 99%

Influence of Carbocation Stability in the Gas Phase on Solvolytic Reactivity: Beyond Bridgehead Derivatives

et al. 2003

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The intrinsic gas-phase stability of bicyclic secondary carbocations has been determined by Dissociative Proton Attachment of chlorides and alcohols, respectively. From these data, Gibbs free energies for hydride transfer relative to 1-adamantyl (Delta(r)G degrees (8,exp)) are derived after application of appropriate leaving group corrections, and good agreement with theoretical values, (Delta(r)G degrees (8,comp)), calculated at the G2(MP2) or MP2/6-311G(d,p) level, is reached (Table 1). The relative rate constants for solvolysis (log(k/k(0))) of the bicyclic secondary derivatives correlate with the stabilities of the respective carbocations in the same manner as tertiary bridgehead derivatives, but simple monoderivatives and acyclic derivatives solvolyze faster than predicted on the grounds of the ion stabilities. The corresponding stabilities of cyclopropyl- and benzyl-substituted carbocations have been obtained by a combination of experimental and computational data available in the literature with computational methods. Correlation of the rate constants for solvolysis vs ion stabilities for these compounds reveals a trend similar to that observed for bridgehead derivatives, but with much more scatter, which is attributed to nucleophilic solvent participation and/or nucleophilic solvation.

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Section: Introductionmentioning

confidence: 99%

Influence of Carbocation Stability in the Gas Phase on Solvolytic Reactivity: Beyond Bridgehead Derivatives

et al. 2003

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ChemInform Abstract: STERIC EFFECTS ON REACTION RATES. IV. EVALUATION OF THE KETONE MODEL FOR THE SOLVOLYSIS TRANSITION STATE OF SECONDARY P‐TOLUENESULFONATES

Mueller¹,

Blanc²,

Perlberger³

1982

Chemischer Informationsdienst

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SummaryThe rates of solvolysis of secondary p-toluenesulfonates in acetic acid or 97% trifluoroethanol are interpreted in terms of strain changes between substrate and the corresponding ketone. Such strain changes are obtained from force-field calculations (AE,,) and from equilibration of alcohols and ketones (AG,,). This simple model reproduces the behaviour of substrates reacting by k,-pathways to afford unstrained carbenium ions. Anchimeric assistance and leaving group hindrance in the transition state are recognized in clear-cut cases by deviations from the expected reactivity. However, the model breaks down when highly strained carbenium ions of the cyclobutyl or 7-norbornyl type are involved.

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Steric Effects on Reaction Rates. VI. Application of a New MM2 Force‐Field for Carbenium Ions to Solvolysis Rates of Secondary p‐Toluenesulfonates

Müller

Mareda

1985

Helvetica Chimica Acta

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An empirical force-field for carbenium ions has been incorporated in Allinger's MM2 programme. Structural parameters of secondary carbenium ions calculated by this method are compared with those obtained with Schleyer's BIGSTRN calculations. The strain changes occurring upon solvolysis of secondary p-toluenesulfonates are evaluated by means of this force-field and correlated with the rate constants for solvolysis. The equation for correlation of acetolysis, relative to cyclohexyl p-toluenesulfonate, of 28 k, substrates is AGZ, = 0.67 AE,, -0.20 (r = 0.958).

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Steric Effects on Reaction Rates. IV. Evaluation of the Ketone Model for the Solvolysis Transition State of Secondary p‐Toluenesulfonates

Cited by 11 publications

References 45 publications

Influence of Carbocation Stability in the Gas Phase on Solvolytic Reactivity: Beyond Bridgehead Derivatives

Influence of Carbocation Stability in the Gas Phase on Solvolytic Reactivity: Beyond Bridgehead Derivatives

ChemInform Abstract: STERIC EFFECTS ON REACTION RATES. IV. EVALUATION OF THE KETONE MODEL FOR THE SOLVOLYSIS TRANSITION STATE OF SECONDARY P‐TOLUENESULFONATES

Steric Effects on Reaction Rates. VI. Application of a New MM2 Force‐Field for Carbenium Ions to Solvolysis Rates of Secondary p‐Toluenesulfonates

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