Interaction Energies and Dynamics of Acid−Base Pairs Isolated in Cavitands

The use of capsules and cavitands in physical organic chemistry is briefly reviewed, and their application to the study of salt bridges is introduced. Carboxylate/ammonium ion pairs are generated within an environment that more or less surrounds the functional groups within a synthetic fixed introve...

Full description

Saved in:
Bibliographic Details
Published in:Journal of organic chemistry 2008-09, Vol.73 (17), p.6480-6488
Main Authors: Purse, Byron W, Butterfield, Sara M, Ballester, Pablo, Shivanyuk, Alexander, Rebek, Julius
Format: Article
Language:English
Subjects:
Amides - chemistry
Amines - chemistry
Carboxylic Acids - chemistry
Chemistry
Coordination compounds
Ethers, Cyclic - chemistry
Exact sciences and technology
Heterocyclic compounds
Heterocyclic compounds with only one n hetero atom and condensed derivatives
Hydrogen Bonding
Hydrophobic and Hydrophilic Interactions
Inorganic chemistry and origins of life
Kinetics
Magnetic Resonance Spectroscopy
Models, Molecular
Organic chemistry
Preparations and properties
Resorcinols - chemistry
Solvents - chemistry
Thermodynamics
Citations: Items that this one cites
Items that cite this one
Online Access:Get full text
Tags: Add Tag
No Tags, Be the first to tag this record!
Description
Summary:The use of capsules and cavitands in physical organic chemistry is briefly reviewed, and their application to the study of salt bridges is introduced. Carboxylate/ammonium ion pairs are generated within an environment that more or less surrounds the functional groups within a synthetic fixed introverted solvent sphere. This is provided by cavitands that fold around amines and present them with a carboxylic acid function. Both organic and water-soluble versions were prepared, and their equilibrium affinities with quinuclidine bases were determined by NMR methods. The association constants range from approximately 103 M−1 in water to more than 105 M−1 in organic solvents. Studies of nitrogen inversion and tumbling of [2.2.2]-diazabicyclooctane within the introverted acids also illustrate the strength of the acid−base interactions. The barriers to in−out exchange of several amine guests were determined to be in the range from 15 to 24 kcal mol−1. Some parallels with enzymes are drawn: the receptor folds around the guest species; presents them with inwardly directed functionality; and provides a generally hydrophobic environment and a periphery of secondary amide bonds.
ISSN:0022-3263
1520-6904
DOI:10.1021/jo8008534