Mechanisms of elimination reactions. 34. Deuterium and nitrogen isotope effects and Hammett correlations in the reaction of (2-arylethyl)trimethylammonium ions with hydroxide ion in mixtures of water and dimethyl sulfoxide
When (2-phenylethyl)trimethylammonium and (2-phenylethyl-2,2-d/sub 2/)trimethylammonium bromides are treated with sodium hydroxide in aqueous dimethyl sulfoxide at 60/sup 0/C, increasing the dimethyl sulfoxide concentration leads to an increase in the elimination rate (> 10/sup 3/ between 17.1% and 57.1% Me/sub 2/SO). There is also an increase in k/sub H/k/sub D/ from 3.22 at 17.1% Me/sub 2/SO to 5.21 at 34.3%, followed by a decrease to 3.83 at 57.1%. The nitrogen isotope effect (k/sub 14//k/sub 15/) decreases initially from ca 1.009 (estimated from data at 97/sup 0/C) in water to 1.007 in 22.8% Me/sub 2/SO but thereafter remains essentially constant around 1.006 to 1.007 up to 57.1% Me/sub 2/SO. When substituted (2-phenylethyl)trimethylammonium bromides (substituents p-Cl, H, p-Me, and p-MeO) are used, the rates fit the Hammett equation. The Hammett rho is + 3.11 in 17.1% Me/sub 2/SO, but after an initial rise it remains essentially constant (+ 3.38 +- 0.09) from 30% to 50.6% Me/sub 2/SO. Both the nitrogen isotope effects and the Hammett rho values indicate a transition state that becomes somewhat more reactant-like with increasing dimethyl sulfoxide concentration. The deuterium isotope effects are consistent with this picture but suggest a greater shift in transition-state structure.
- Research Organization:
- Univ. of Rochester, NY
- OSTI ID:
- 5769147
- Journal Information:
- J. Org. Chem.; (United States), Journal Name: J. Org. Chem.; (United States) Vol. 46:21; ISSN JOCEA
- Country of Publication:
- United States
- Language:
- English
Similar Records
Mechanisms of elimination reactions. 30. The contributions of tunneling and heavy-atom motion in the reaction coordinate to deuterium kinetic isotope effects in eliminations from 2-phenylethyl derivatives
Mechanisms of elimination reactions. Part 37. Secondary. beta. -tritium isotope effects in eliminations from 2-arylethyl derivatives
Related Subjects
400302* -- Organic Chemistry-- Isotope Effects-- (-1987)
AMINES
AMMONIUM COMPOUNDS
CHARGED PARTICLES
CHEMICAL REACTIONS
DATA
DEUTERIUM
DMSO
EXPERIMENTAL DATA
HYDROGEN COMPOUNDS
HYDROGEN ISOTOPES
HYDROXIDES
INFORMATION
IONS
ISOTOPE EFFECTS
ISOTOPES
LIGHT NUCLEI
NITROGEN 15
NITROGEN ISOTOPES
NUCLEI
NUMERICAL DATA
ODD-EVEN NUCLEI
ODD-ODD NUCLEI
ORGANIC COMPOUNDS
ORGANIC SULFUR COMPOUNDS
OXYGEN COMPOUNDS
QUATERNARY COMPOUNDS
SOLVENT PROPERTIES
STABLE ISOTOPES
SULFOXIDES
WATER