Remarkably large solvolytic rate enhancement due to relief of ground state leaving group strain

Slutsky, Joel; Bingham, Richard C.; Schleyer, Paul von Ragué; Dickason, William C.; Brown, Herbert C.

doi:10.1021/ja00813a071

Cited by 56 publications

(20 citation statements)

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“…This relief of F-strain has been proposed as a major factor in certain ionic reactions (24,25). However, the formation of acids in the present reactions shows that the bond between the phenyl ring and the carboxyl group is not broken in the rate-determining step of these reactions (eq.…”

Section: Discussionmentioning

confidence: 88%

Steric Crowding and the Reactivity of Substituted tert-Butyl Perbenzoates

Icli¹,

Kandil²,

Thankachan³

et al. 1975

Can. J. Chem.

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SIDDICK ICLI, UNDIL A. KANDIL, C. THANKACHAN, and THOMAS T. TIDWELL. Can. J. Chem. 53,979 (1975).The relative rates of decomposition of peroxyesters in cumene at 100" and their activation parameters AH* (kcal/mol) and ASf (cal deg-I mol-') were tert-butyl perbenzoate (1) 1.0, 34.0, 9.3; tert-butyl pertoluate (7) 1.3, 32.2, 4.8; tert-butyl permesitoate (8) 11, 31.9, 8.4; and tert-butyl2,4,6-tri-tert-butylperbenzoate (9) 29, 32.9, 13.0. Each peroxyester yielded the corresponding acid as one of the products. The reactions are all interpreted as proceeding through a rate-determining scission of the 0-0 bond to yield a benzoyloxy radical, which then undergoes competitive decarboxylation and hydrogen abstraction from the solvent. The small rate acceleration due to apara substituent is interpreted as due to a polar factor and the larger rate enhancing effect of the ortho substituents is interpreted as due to destabilization of the ground state due to twisting of the carboxyl group out of conjugation with the ring. perbenzoate de tert-butyle (9) 29, 32.9, 13.0. Chaque peroxyester conduit entre autre ii l'acide correspondant. On interprete toutes les reactions en fonction d'une Ctape dkterminante de la reaction qui impliquerait la scission du lien 0-0 conduisant au radical benzoyloxy qui subirait ensuite une decarboxylation ou enleverait un hydrogene du solvant. On attribue la petite augmentation de vitesse due ii un substituant en para a des facteurs polaires; par ailleurs l'augmentation importante observee lorsqu'il y a des substituants en position ortho implique une dtstabilisation de 1'6tat fondamental due ii une rotation du groupement carboxyle hors du plan de conjugaison du cycle.[Traduit par le journal]

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Section: Discussionmentioning

confidence: 88%

Steric Crowding and the Reactivity of Substituted tert-Butyl Perbenzoates

Icli¹,

Kandil²,

Thankachan³

et al. 1975

Can. J. Chem.

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“…With CH, and CH,CH,O the deviation is in the order of 10 kcal/mol. The chloro derivative (13-C1) solvolyzes with the relative rate of 0.06 compared to the cis-cis-trans-isomer (14-Cl); however, with p-nitrobenzoates as leaving group the relative rate of 13-PNBO is 200 [4]. These tendencies are reproduced by the force-field calculations using the acetate group as model for PNBO (Scheme).…”

Section: ' )mentioning

confidence: 96%

“…30 kcal/mol upon changing the substituents 121. F-Strain effects may also appear in solvolysis reactions of crowded substrates [I] [3]; the most striking observations in this area has been reported by u. Schleyer and his coworkers [4] (see below).…”

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confidence: 99%

Steric Effects on Reaction Rates. Part VIII. The Significance of Front Strain Release in Solvolysis of Bridgehead Derivatives

Müller

Blanc

Mareda

1986

Helvetica Chimica Acta

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The steric requirements of leaving groups for 14 bridgehead derivatives have been examined using MM2 calculations. The strain varies almost monotonously throughout the series upon variation of the leaving group from H to C1, OH, CH3, CH3CH2O, (CH3)3CO, (CH3)3C and no significant trends for differential F-strain effects are detected expect for the perhydrophenalene derivative 13. The experimental rates of solvolysis of bridgehead derivatives correlate well with the calculated steric energy differences between substrate R-X and the corresponding carbenium ion R. However, the strain calculations using the more recent force-fields (MM2) disagree, in part, with those reported in the literature: chloride and p-toluenesulfonate leaving groups correlate with identical slopes, and the perhydrotriquinacene derivative 10 shows no anomalous behavior. The calculations suggest that F-strain and C,C-hyperconjugation should not play any dominant role in bridgehead solvolysis

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“…In these cases, the free enthalpies of activation for the thermolyses must be statistically corrected for the number of equivalent bonds and the bond types must be taken into account [C,-C,: (19). f-'' C,-C,: (18), (20)…”

Section: Thermal Stability and Strain Enthaipymentioning

confidence: 99%

Towards an Understanding of the Carbon‐Carbon Bond

Rüchardt

Beckhaus

1980

Angew. Chem. Int. Ed. Engl.

146

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Dedicated to Professor Rorf Huisgen on the occasion of his 60th birthdayIn this essay, the classical question of "the influence of the number and kind of substituents on the strength of the C-C bond", is pursued with the modern tools of contemporary physical organic chemistry. Based on the work of Karl Ziegler, the products and kinetics of thermolysis of a large number of highly branched aliphatic hydrocarbons and phenyl-or cyano-substituted derivatives were investigated. For each class of compounds, a linear relationship was found between the free enthalpy of activation of the homolytic cleavage of the weakest C-C bond and the strain energy in the ground state. These relationships permitted a quantitative separation of steric and electronic effects on the cleavage of C-C bonds. The influence of the size of the substituent groups on bond angles, bond lengths, and the conformational behavior of model compounds was studied by means of experimental structure determinations and force field calculations. C-C bond lengths up to 164 pm, bond angles at tetracoordinate carbon as large as 126", and unusual eclipsed and gauche preferred conformations were found.

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Remarkably large solvolytic rate enhancement due to relief of ground state leaving group strain

Cited by 56 publications

References 0 publications

Steric Crowding and the Reactivity of Substituted tert-Butyl Perbenzoates

Steric Crowding and the Reactivity of Substituted tert-Butyl Perbenzoates

Steric Effects on Reaction Rates. Part VIII. The Significance of Front Strain Release in Solvolysis of Bridgehead Derivatives

Towards an Understanding of the Carbon‐Carbon Bond

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