A new method of accurate pK_b determinations for some organic amines

Abstract

ABSTRACT:The accurate pK b determinations for some amines have been investigated using the combination of the extended clusters-continuum model with the polarizable continuum solvation model. The formation of molecular clusters by means of the amines wrapped up with water molecules leads to the weakness of the mutual function between the polar solvents and the amines, and, hence, the accuracy of pK b has been enhanced by using a coherent and well-defined approach without external approximations or experimental data. The calculations are performed at the HF/6-311ϩϩG(d, p) level and agreed well with experimental data because electron correlation effect cancels mutually in the calculated value of ⌬G which is not an absolute value, but a relative value. © 2007 Wiley Periodicals, Inc. Int J Quantum Chem 108: [265][266][267][268][269][270][271] 2008

Characterization of Redox States of Ru(OH2)(Q)(tpy)2+ (Q = 3,5-di-tert-butyl-1,2-benzoquinone, tpy = 2,2′:6′,2″-terpyridine) and Related Species through Experimental and Theoretical Studies

“…The detailed procedure for calculating p K a and choosing the values of G g o (H + ) and Δ G s * (H + ) has been thoroughly discussed in the literature. − It should be noted that the Δ G s * values reported in the current study do not account for differences in the thermal correction between the gas phase and aqueous phase owing to the difficulty of converging the geometry optimizations in the aqueous phase, i.e., no vibrational frequency analysis was carried out with the continuum solvation model. It is expected that the difference in the thermal correction between the gas and aqueous phases for each intermediate complex will be quite small because no significant geometric change was observed during the first 10 geometry optimization iterations in solution.…”

Modern methods for estimation of ionization constants of organic compounds in solution

“…Explicit/implicit solvent model (or cluster continuum model) is a combination of the above described continuum and cluster models for the calculation of pK a 's [44,50,55,59,66,98,99,102,106,144,145]; this model simultaneously takes into account field ef- Fig. 6.…”

“…(10), n → is the vector orthogonal to the cavity surface and directed outward, the subscript "in" refers to the internal side of the cavity boundary, and ε is the dielectric constant of the medium. The original formulation of PCM (DPCM) was used to predict pK a 's in [45,62,74,79,[84][85][86][87][96][97][98][99]. At present, pK a 's are calculated mainly using PCM modifications briefly described below.…”