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https://hdl.handle.net/2440/17800
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Type: | Journal article |
Title: | Aminocyclodextrins to facilitate the deprotonation of 4-tert-butyl-α-nitrotoluene |
Other Titles: | Aminocyclodextrins to facilitate the deprotonation of 4-tert-butyl-alpha-nitrotoluene |
Author: | Barr, L. Easton, C. Lee, K. Lincoln, S. |
Citation: | Organic and Biomolecular Chemistry, 2005; 3(16):2990-2993 |
Publisher: | Royal Soc Chemistry |
Issue Date: | 2005 |
ISSN: | 1477-0520 1477-0539 |
Statement of Responsibility: | Lorna Barr, Christopher J. Easton, Kitty Lee and Stephen F. Lincoln |
Abstract: | 6A-Amino-6A-deoxy-beta-cyclodextrin enhances the rate of the deprotonation of 4-tert-butyl-alpha-nitrotoluene. The rate constants for reaction of the cyclodextrin-bound species, kinc = 4 x 10(-3), 9 x 10(-3) and 19 x 10(-3) s(-1), at pH 6.0, 6.5 and 7.0, respectively, in 0.1 mol dm(-3) aqueous phosphate buffer containing 1% methanol at 298 K. These rate constants correspond to a rate acceleration (kinc/kun) of ca. 10 times at each pH. Under the same conditions, 6A-dimethylamino-6A-deoxy-beta-cyclodextrin and 6A-(2-aminoethylamino)-6A-deoxy-beta-cyclodextrin are more effective; at pH 6.0, 6.5 and 7.0, for the former, kinc = 3 x 10(-2), 7 x 10(-2) and 12 x 10(-2) s(-1), whilst for the latter, kinc = 4 x 10(-2), 5 x 10(-2) and 9 x 10(-2) s(-1), respectively. Each cyclodextrin also decreases the pKa of the nitrotoluene, from 6.8 in free solution, to 6.2 when bound. The accelerated deprotonation by 6A-amino-6A-deoxy-beta-cyclodextrin is reflected in the enhanced rates of hydrogen-deuterium exchange of the nitrotoluene in deuterium oxide, and in the conjugate addition of the nitrotoluene to methyl vinyl ketone in aqueous solution. |
Keywords: | Toluene Cyclodextrins Hydrogen-Ion Concentration |
Rights: | © Royal Society of Chemistry 2005 |
DOI: | 10.1039/b506187c |
Published version: | http://dx.doi.org/10.1039/b506187c |
Appears in Collections: | Aurora harvest 2 Chemistry publications Environment Institute publications |
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