Synthesis and solvolysis of derivatives of 7-methyl-7-hydroxynorbornane and the epimeric 7-methyl-7-hydroxynorbornenes

Gassman, Paul G.; Pascone, John M.

doi:10.1021/ja00804a042

Cited by 37 publications

(8 citation statements)

References 2 publications

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“…The third point was for the anti-7-norbornenyl system for which our results given above indicate good agreement with the SBS correlation. However, we disagree both with respect to the Me/H ratio which was obtained by a rather elaborate extrapolation (see ref 17 on p 7803 of ref 12) and with the reported «-CH3/CD3 isotope effect. This effect was observed in the pnitrobenzoates solvolyzed at 135°in 70% aqueous dioxane where complications due to acylcarbon oxygen cleavage may arise.…”

Section: Methods and Resultscontrasting

confidence: 78%

Methyl-d3 isotope effects, .alpha.-methyl hydrogen rate effects, and the analysis of some solvolytic reaction mechanisms

Fisher¹,

Seib²,

Shiner³

et al. 1975

J. Am. Chem. Soc.

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Section: Methods and Resultscontrasting

confidence: 78%

Methyl-d3 isotope effects, .alpha.-methyl hydrogen rate effects, and the analysis of some solvolytic reaction mechanisms

Fisher¹,

Seib²,

Shiner³

et al. 1975

J. Am. Chem. Soc.

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“…On the other hand, the value obtained for the β-KIE (1/ B ) of 2/hydrogen atom is unprecedented. The direction of change (greater value for the less stable cationic species) is as expected, but the magnitude indicates an enormous demand for hyperconjugative stabilization by the β-hydrogen in the formation of the dication. , …”

Section: Resultssupporting

confidence: 63%

“…To simplify the calculations (because no optimization program was available, the parameters were varied by typing in the new values for each calculations), the same value for the primary isotope effect for elimination from ions 3 and 4 was taken (denoted as P ). The initial guess for the primary KIE could be anywhere between 2 and 9, with the most likely range between 4 and 7. , For the β-secondary KIE, values between 1.05 and 1.33 have been reported, , with the value reported to increase as the demand for electrons by the carbocationic center increases . This quantity was expressed in the computer program by a parameter B , defined as β-KIEA = 1/ B .…”

Section: Resultsmentioning

confidence: 99%

Carbodications. 4.¹ Hydrogen Isotope Exchange of Crotonyl Cations in Superacid

1996

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The title ion reacts in 1:1 DF-SbF(5) and exchanges up to five protium atoms with deuterium. The incorporation of label was measured by GC-MS analysis of the methyl crotonate formed by methanol quenching. The isotopomer distribution at about 60% conversion, which shows a minimum for the d(1) and a maximum for the d(4) species, indicates that the intermediate dication with the second charge at C(3) loses a proton faster from C(4) than from C(2). Formation of the pentadeuteriocrotonyl cation indicates that the 1,4-dication (acyl primary alkyl) or the 1,2-dication must intervene in the process. Computer modeling of the kinetics for the multiple exchange process to fit the experimental deuterium distribution allowed determination of the relative rate constants and isotope effects (KIEs) for the formation of the carbocations from alkenoyl cations (beta-secondary KIE) and elimination from carbodications to alkenoyl cations (primary KIE). An exceptionally large beta-secondary KIE of ca. 2.0/hydrogen was found for the formation of the dication. A small primary isotope effect of ca. 1.5 was found for elimination from the dications to the alkenoyl cations. Elimination from the 1,3-acylalkyl dication to form the nonconjugated 3-butenoyl cation is 6-7 times faster than elimination to the conjugated 2-butenoyl cation. The rate ratio for the conversion of 3-butenoyl cation to the 1,4-dication (primary alkyl cation) and 1,3-dication (secondary alkyl cation) is (0.025-0.030):1, whereas the relative rate of the formation of the 1,2-acylalkyl dication (the alternative route of achieving pentadeuteration) is zero.

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“…However, even if all elimination products obtained upon solvolysis of 17 and 19 (51-71 and 7-33 YO, resp.) [8] [9] are formed by an E2 pathway, this will influence the rate constants for solvolysis only by a factor of 1-3. This is insignificant in view of the overall reactivity scale.…”

Section: Gmentioning

confidence: 99%

Steric Effects on Reaction Rates. Part IX. Force‐Field Parameters for Bridgehead and Rigid Tertiary Carbenium Ions

Müller¹,

Mareda²

1987

Helvetica Chimica Acta

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Molecular-mechanics calculations for strain of carbenium ions are tested using Bentley's unified reactivity scale for bridgehead solvolysis as reference. Excellent correlations are obtained for solvolytic bridgehead reactivity with the calculated steric-energy difference (?Est) between substrate (R--H or R--OH) and cation (R+). After adjustment of appropriate force-field parameters, the approach is successfully extended to the rigid, but planar cations derived from structures 15-20; however, the general set of parameters cannot be applied to highly strained systems such as the cation formed from 17. With all of the 18 sets of parameters tested, the 2-endo-norbornyl derivative 16, is adequately correlated, while the exo isomer 15 exhibits enhanced reactivity by a factor of ca. 102 to 103

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Synthesis and solvolysis of derivatives of 7-methyl-7-hydroxynorbornane and the epimeric 7-methyl-7-hydroxynorbornenes

Cited by 37 publications

References 2 publications

Methyl-d3 isotope effects, .alpha.-methyl hydrogen rate effects, and the analysis of some solvolytic reaction mechanisms

Methyl-d3 isotope effects, .alpha.-methyl hydrogen rate effects, and the analysis of some solvolytic reaction mechanisms

Carbodications. 4.¹ Hydrogen Isotope Exchange of Crotonyl Cations in Superacid

Steric Effects on Reaction Rates. Part IX. Force‐Field Parameters for Bridgehead and Rigid Tertiary Carbenium Ions

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Synthesis and solvolysis of derivatives of 7-methyl-7-hydroxynorbornane and the epimeric 7-methyl-7-hydroxynorbornenes

Cited by 37 publications

References 2 publications

Methyl-d3 isotope effects, .alpha.-methyl hydrogen rate effects, and the analysis of some solvolytic reaction mechanisms

Methyl-d3 isotope effects, .alpha.-methyl hydrogen rate effects, and the analysis of some solvolytic reaction mechanisms

Carbodications. 4.1 Hydrogen Isotope Exchange of Crotonyl Cations in Superacid

Steric Effects on Reaction Rates. Part IX. Force‐Field Parameters for Bridgehead and Rigid Tertiary Carbenium Ions

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Carbodications. 4.¹ Hydrogen Isotope Exchange of Crotonyl Cations in Superacid