First principles calculations of aqueous pKa values for organic and inorganic acids using COSMO-RS reveal an inconsistency in the slope of the pKa scale

被引:254
作者
Klamt, A
Eckert, F
Diedenhofen, M
Beck, ME
机构
[1] COSMOlog GMBH & COKG, D-51381 Leverkusen, Germany
[2] Bayer Cropsci, BCS, R, SCLA, D-40789 Monheim, Germany
关键词
D O I
10.1021/jp034688o
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
The COSMO-RS method, a combination of the quantum chemical dielectric continuum solvation model COSMO with a statistical thermodynamics treatment for more realistic solvation (RS) simulations, has been used for the direct prediction of pK(a), constants of a large variety of 64 organic and inorganic acids. A highly significant correlation of r(2) = 0.984 with a standard deviation of only 0.49 between the calculated values of the free energies of dissociation and the experimental pK(a) values was found, without any special adjustment of the method. Thus, we have a theoretical a priori prediction method for pK(a), which has the regression constant and the slope as only adjusted parameters. Such a method can be of great value in many areas of physical chemistry, especially in pharmaceutical and agrochemical industry. To our surprise, the slope of pKa vs DeltaG(diss) is only 58% of the theoretically expected value of 1/RTln(10). A careful analysis with respect to different contributions as well as a comparison with the work of other authors excludes the possibility that the discrepancy is due to weaknesses of the calculation method. Hence, we must conclude that the experimental pK(a) scale depends differently on the free energy of dissociation than generally assumed.
引用
收藏
页码:9380 / 9386
页数:7
相关论文
共 93 条
[1]   New density functional and atoms in molecules method of computing relative pKa values in solution [J].
Adam, KR .
JOURNAL OF PHYSICAL CHEMISTRY A, 2002, 106 (49) :11963-11972
[2]   ELECTRONIC-STRUCTURE CALCULATIONS ON WORKSTATION COMPUTERS - THE PROGRAM SYSTEM TURBOMOLE [J].
AHLRICHS, R ;
BAR, M ;
HASER, M ;
HORN, H ;
KOLMEL, C .
CHEMICAL PHYSICS LETTERS, 1989, 162 (03) :165-169
[3]  
Ahlrichs R., 2002, TURBOMOLE VERSION 5
[4]   INCORPORATION OF SOLVENT EFFECTS INTO DENSITY-FUNCTIONAL CALCULATIONS OF MOLECULAR-ENERGIES AND GEOMETRIES [J].
ANDZELM, J ;
KOLMEL, C ;
KLAMT, A .
JOURNAL OF CHEMICAL PHYSICS, 1995, 103 (21) :9312-9320
[5]   Site of ionization of polyfunctional bases and acids .1. Ab initio proton affinities [J].
Bagno, A ;
Scorrano, G .
JOURNAL OF PHYSICAL CHEMISTRY, 1996, 100 (05) :1536-1544
[6]   On the acidity and reactivity of HNO in aqueous solution and biological systems [J].
Bartberger, MD ;
Fukuto, JM ;
Houk, KN .
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA, 2001, 98 (05) :2194-2198
[7]  
BATOULIS J, 1993, UNPUB BAYER RES REPO
[8]  
BECK ME, 2002, EUROQSAR 2002 C BOUR
[9]   DENSITY-FUNCTIONAL THERMOCHEMISTRY .3. THE ROLE OF EXACT EXCHANGE [J].
BECKE, AD .
JOURNAL OF CHEMICAL PHYSICS, 1993, 98 (07) :5648-5652
[10]   DENSITY-FUNCTIONAL EXCHANGE-ENERGY APPROXIMATION WITH CORRECT ASYMPTOTIC-BEHAVIOR [J].
BECKE, AD .
PHYSICAL REVIEW A, 1988, 38 (06) :3098-3100