Molecular recognition of alkyl- and arylakyl-amines in dischloromethane and chloroform by calix[4]-crown ethers
- 1 January 1995
- journal article
- research article
- Published by Royal Society of Chemistry (RSC) in Journal of the Chemical Society, Perkin Transactions 2
- No. 11,p. 2031-2034
- https://doi.org/10.1039/p29950002031
Abstract
The calix[4]-crown-6 ether 2 exhibited pronounced molecular recognition properties toward alkylamines. –ΔG° values obtained for the solvent extraction of alkylamines into dichloromethane by compound 2 ranged up to 9.7. kcal mol–1. This binding strength generally decreased with the increasing size of the alkyl chain of the ammonium guest. 1H NMR titrations of compound 2 with alkyl- or arylalkyl-ammonium guest in CDCl3 revealed that the primary binding site is the central part of the crown moiety. Host 2 exhibited a much larger discrimination than the dibenzo-18-crown-6 ether, favouring linear over other isomeric amines. Transport selectivity between buty- and tert-butyl-ammonium guests was found to be greater than a 70-fold excess, as assessed by the competitive transport through chloroform liquid membrane.Keywords
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