The effect of cation size on ion pairing of methyl orange dye with tetraalkylammonium and benzyltrialkylammonium ions in aqueous solution |
| |
Authors: | Richard L Reeves Hyman L Cohen Shelley A Harkaway C Jameson Kaiser |
| |
Institution: | (1) Research Laboratories, Eastman Kodak Co., 14650 Rochester, New York;(2) Present address: Department of Chemistry, East High School, 14650 Rochester, New York |
| |
Abstract: | Formation constants have been measured by a solvent distribution method for the ion pairing of an arene sulfonate, methyl orange dye, with two series of quaternary ammonium ions: R4N+(R=Et,n-Pr,n-Bu, andn-Pent) and C6H5CH2R3N+ (R=Me, Et,n-Pr,n-Bu,n-Pent, andn-Hex). Ion pairing increases dramatically as the length of the R group increases beyond butyl. Using a hard-sphere model for contact ion pairs, it is estimated that coulombic attraction contributes about –kT to the binding free energy and decreases slightly with increasing size of R4N+. Other factors related to solvation effects, of which cosphere overlap predominates, contribute from –2kT to –7kT of binding energy. Plots of logK for association as a function of cation size show an inflection with decreasing slope between R=propyl and R=butyl. Possible causes for the inflection are considered. |
| |
Keywords: | ion-pair formation ion-size effect dye sulfonate tetraalkylammonium ions benzyltrialkylammonium ions solvent extraction |
本文献已被 SpringerLink 等数据库收录! |
|