Medium effects on the rates of stereomutation of a pair of diastereomeric cyclopropanones. Ground state stabilization in nucleophilic solvents induces deviation from solvent polarity controlled behavior

Matthew Hj Cordes, Jerome A. Berson

Research output: Contribution to journalArticle

18 Citations (Scopus)

Abstract

The synthesis of the two stereoisomers of spiro(bicyclo[2.2.1]heptane-2,1'-cyclopropan)-2'-one, 3a and 4a, from diazomethane and the ketene 2-carbonylylbicyclo[2.2.1]heptane in ether at 195 K yields a ~1.6 to 1 ratio. At 245 K, the ratio changes in a first-order manner, with an observed rate constant of 1.7 x 10-4 s-1, to an equilibrium ratio of 0.8 to 1. The temperature dependence of the interconversion of 3a and 4a (GC method) and that of their dideuterio derivatives 3b and 4b (NMR method) have been determined and yield activation parameters E(a) = 16.3 ± 1.4 kcal/mol and log A = 10.4 ± 1.4 (A in s-1) (GC method) and E(a) = 15.3 ± 1.4 and log A = 9.6 ± 1.4 (NMR method). The free energies of activation at 239 K have been determined in four solvents: dichloromethane (16.1 kcal/mol), acetone (17.7), hexane (17.9), and ether (19.1). The solvent dependence does not correlate well with commonly used measures of solvent polarity, and the reaction is unexpectedly slow in acetone and ether. This deceleration is explained in terms of nucleophilic association of these solvents with the carbonyl groups in the cyclopropanones, leading to a ground state stabilization.

Original languageEnglish (US)
Pages (from-to)6241-6251
Number of pages11
JournalJournal of the American Chemical Society
Volume118
Issue number26
DOIs
StatePublished - Jul 3 1996
Externally publishedYes

Fingerprint

Ground state
Stabilization
Ether
Ethers
Heptane
Acetone
Chemical activation
Nuclear magnetic resonance
Diazomethane
Heptanes
Stereoisomerism
Deceleration
Methylene Chloride
Dichloromethane
Hexanes
Hexane
Free energy
Rate constants
Association reactions
Derivatives

ASJC Scopus subject areas

  • Chemistry(all)

Cite this

@article{08280cc6b9aa452c8e6a703fbfa36b68,
title = "Medium effects on the rates of stereomutation of a pair of diastereomeric cyclopropanones. Ground state stabilization in nucleophilic solvents induces deviation from solvent polarity controlled behavior",
abstract = "The synthesis of the two stereoisomers of spiro(bicyclo[2.2.1]heptane-2,1'-cyclopropan)-2'-one, 3a and 4a, from diazomethane and the ketene 2-carbonylylbicyclo[2.2.1]heptane in ether at 195 K yields a ~1.6 to 1 ratio. At 245 K, the ratio changes in a first-order manner, with an observed rate constant of 1.7 x 10-4 s-1, to an equilibrium ratio of 0.8 to 1. The temperature dependence of the interconversion of 3a and 4a (GC method) and that of their dideuterio derivatives 3b and 4b (NMR method) have been determined and yield activation parameters E(a) = 16.3 ± 1.4 kcal/mol and log A = 10.4 ± 1.4 (A in s-1) (GC method) and E(a) = 15.3 ± 1.4 and log A = 9.6 ± 1.4 (NMR method). The free energies of activation at 239 K have been determined in four solvents: dichloromethane (16.1 kcal/mol), acetone (17.7), hexane (17.9), and ether (19.1). The solvent dependence does not correlate well with commonly used measures of solvent polarity, and the reaction is unexpectedly slow in acetone and ether. This deceleration is explained in terms of nucleophilic association of these solvents with the carbonyl groups in the cyclopropanones, leading to a ground state stabilization.",
author = "Cordes, {Matthew Hj} and Berson, {Jerome A.}",
year = "1996",
month = "7",
day = "3",
doi = "10.1021/ja960481f",
language = "English (US)",
volume = "118",
pages = "6241--6251",
journal = "Journal of the American Chemical Society",
issn = "0002-7863",
publisher = "American Chemical Society",
number = "26",

}

TY - JOUR

T1 - Medium effects on the rates of stereomutation of a pair of diastereomeric cyclopropanones. Ground state stabilization in nucleophilic solvents induces deviation from solvent polarity controlled behavior

AU - Cordes, Matthew Hj

AU - Berson, Jerome A.

PY - 1996/7/3

Y1 - 1996/7/3

N2 - The synthesis of the two stereoisomers of spiro(bicyclo[2.2.1]heptane-2,1'-cyclopropan)-2'-one, 3a and 4a, from diazomethane and the ketene 2-carbonylylbicyclo[2.2.1]heptane in ether at 195 K yields a ~1.6 to 1 ratio. At 245 K, the ratio changes in a first-order manner, with an observed rate constant of 1.7 x 10-4 s-1, to an equilibrium ratio of 0.8 to 1. The temperature dependence of the interconversion of 3a and 4a (GC method) and that of their dideuterio derivatives 3b and 4b (NMR method) have been determined and yield activation parameters E(a) = 16.3 ± 1.4 kcal/mol and log A = 10.4 ± 1.4 (A in s-1) (GC method) and E(a) = 15.3 ± 1.4 and log A = 9.6 ± 1.4 (NMR method). The free energies of activation at 239 K have been determined in four solvents: dichloromethane (16.1 kcal/mol), acetone (17.7), hexane (17.9), and ether (19.1). The solvent dependence does not correlate well with commonly used measures of solvent polarity, and the reaction is unexpectedly slow in acetone and ether. This deceleration is explained in terms of nucleophilic association of these solvents with the carbonyl groups in the cyclopropanones, leading to a ground state stabilization.

AB - The synthesis of the two stereoisomers of spiro(bicyclo[2.2.1]heptane-2,1'-cyclopropan)-2'-one, 3a and 4a, from diazomethane and the ketene 2-carbonylylbicyclo[2.2.1]heptane in ether at 195 K yields a ~1.6 to 1 ratio. At 245 K, the ratio changes in a first-order manner, with an observed rate constant of 1.7 x 10-4 s-1, to an equilibrium ratio of 0.8 to 1. The temperature dependence of the interconversion of 3a and 4a (GC method) and that of their dideuterio derivatives 3b and 4b (NMR method) have been determined and yield activation parameters E(a) = 16.3 ± 1.4 kcal/mol and log A = 10.4 ± 1.4 (A in s-1) (GC method) and E(a) = 15.3 ± 1.4 and log A = 9.6 ± 1.4 (NMR method). The free energies of activation at 239 K have been determined in four solvents: dichloromethane (16.1 kcal/mol), acetone (17.7), hexane (17.9), and ether (19.1). The solvent dependence does not correlate well with commonly used measures of solvent polarity, and the reaction is unexpectedly slow in acetone and ether. This deceleration is explained in terms of nucleophilic association of these solvents with the carbonyl groups in the cyclopropanones, leading to a ground state stabilization.

UR - http://www.scopus.com/inward/record.url?scp=0030040081&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=0030040081&partnerID=8YFLogxK

U2 - 10.1021/ja960481f

DO - 10.1021/ja960481f

M3 - Article

AN - SCOPUS:0030040081

VL - 118

SP - 6241

EP - 6251

JO - Journal of the American Chemical Society

JF - Journal of the American Chemical Society

SN - 0002-7863

IS - 26

ER -