title: Local polarity in CO2-expanded acetonitrile: a nucleophilic substitution reaction and solvatochromic probes.
abstract: Many processes that use highly tunable gas-expanded liquids (GXLs) rely on the fact that CO2 addition can greatly affect the polarity of the solvent. We have examined several measures of bulk and local polarity in CO2-expanded acetonitrile to enable more effective exploitation of these polarity changes. The rate of the nucleophilic substitution reaction of tributylamine with methyl p-nitrobenzenesulfonate has been analyzed as a function of solvent composition by using in situ high-pressure UV/vis spectroscopy. We have also measured solvatochromic properties including the Kamlet-Taft pi* parameter and Kosower's Z-value. We correlate these local polarity-based kinetic and solvatochromic measures to develop a better understanding of these property changes as a function of bulk and local solvent composition. The data suggest that local composition enhancement in CO2-expanded acetonitrile has a significant impact on the reaction kinetics.
authors: School of Chemical & Biomolecular Engineering, Georgia Institute of Technology, Atlanta, Georgia 30332-0100, USA.
authors: Jackson W
authors: JW
authors: Ford
authors: Malina E
authors: ME
authors: Janakat
authors: Jie
authors: J
authors: Lu
authors: Charles L
authors: CL
authors: Liotta
authors: Charles A
authors: CA
authors: Eckert