Long-range proton transfer in aqueous acid-base reactions

被引：123

作者：

Siwick, B. J. ^{[1
]}

Cox, M. J. ^{[1
]}

Bakker, H. J. ^{[1
]}

机构：

[1] FOM, Inst AMOLF, NL-1098 SJ Amsterdam, Netherlands

来源：

JOURNAL OF PHYSICAL CHEMISTRY B | 2008年 / 112卷 / 02期

关键词：

D O I：

10.1021/jp075663i

中图分类号：

O64 [物理化学（理论化学）、化学物理学];

学科分类号：

070304 ; 081704 ;

摘要：

We study the mechanism of proton transfer (PT) in the aqueous acid-base reaction between the photoacid 8-hydroxy-1,3,6-pyrenetrisulfonic acid (HPTS) and acetate by probing the vibrational resonances of HPTS, acetate, and the hydrated proton with ferntosecond mid-infrared laser pulses. We find that PT takes place in a distribution of hydrogen-bound reaction complexes that differ in the number of water molecules separating the acid and the base. The number of intervening water molecules ranges from 0 to 5, which, together with a strongly distance-dependent PT rate, explains the observed highly nonexponential reaction kinetics. The kinetic isotope effect for the reaction is determined to be 1.5, indicating that tunneling does not play a significant role in the transfer of the proton. Rather, the transfer mechanism is best described in terms of the adiabatic PT picture as it has been formulated by Hynes and co-workers [Staib, A.; Borgis, D.; Hynes, J. T. J. Chem. Phys. 1995, 102, 2487. Ando, K.; Hynes, J. T. J. Phys. Chem. B 1997, 101, 10464.], where solvent fluctuations play an essential role in forming the correct hydrogen-bond configuration and solvent polarization to facilitate PT.

引用

页码：378 / 389

页数：12

共 48 条

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