Enhancement of the Proton Exchange Rate in Aqueous Solution by Small Amounts of Hydrophobic Substances, as Determined from Ultrasonic Relaxation
作者:
C. U. Nicola,
A. Labhardt,
G. Schwarz,
期刊:
Berichte der Bunsengesellschaft für physikalische Chemie
(WILEY Available online 1979)
卷期:
Volume 83,
issue 1
页码: 43-47
ISSN:0005-9021
年代: 1979
DOI:10.1002/bbpc.19790830109
出版商: Wiley‐VCH Verlag GmbH&Co. KGaA
数据来源: WILEY
摘要:
AbstractThe kinetics of the proton transfer reaction between dihydrogen phosphate and imidazole in water with some added methanol, ethanol, and dioxan, respectively, was investigated by means of ultrasonic absorption and velocity dispersion measurements in the frequency range from 0.5 to 36 MHz. The system exhibits a single chemical relaxation time. It reflects a diffusion controlled direct transfer mechanism. The two rate constants have been evaluated as a function of the volume percentage of the added solvent. Both show a sharp maximum at about 0.5%. This effect turned out to be the more pronounced the more hydrophobe the foreign molecules are. Comparatively few molecules of such material therefore seem to appreciably increase the hydrogen bonded water structure in the hydration shells through which proton transfer is mediated.
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