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RECORD NUMBER: 29 OF 287

OLS Field Name OLS Field Data
Main Title Calculations of pK Differences between Structurally Similar Compounds.
Author Rashin, A. A. ; Rabinowitz, J. R. ; Bandelder., J. R. ;
CORP Author Health Effects Research Lab., Research Triangle Park, NC. ;Mount Sinai School of Medicine, New York.;National Science Foundation, Washington, DC.
Publisher c1990
Year Published 1990
Report Number EPA/600/J-90/085;
Stock Number PB90-245408
Additional Subjects Nuclear binding energy ; Molecular structure ; Enthalpy ; Mutations ; Hydration ; Histamines ; Imidazoles ; Reprints ; Competitive binding ; Neuroregulators
Holdings
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Status
NTIS  PB90-245408 Most EPA libraries have a fiche copy filed under the call number shown. Check with individual libraries about paper copy. NTIS 12/03/1990
Collation 7p
Abstract
An attempt is made to find out whether accurate calculations of pK differences in series of biologically active compounds are feasible. The computational method used employs a combination of quantum mechanical calculations of the vacuum proton affinities, and a new method for calculation of hydration energies based on a continuum representation of the solvent. Application of the method to the calculations of pK differences between congeners of imidazolium shown that experimental values of such differences can be computationally predicted within one pK unit for pairs of congeners differing in the hydrogen to methyl substitution or in the position of the same substituent in the molecule. However, calculated values deviate from the experimental ones by more than four pK units for the pairs of congeners differing in the substitution of the hydrogen or methyl group to chloro- or nitro- group. The deviations from experimental values found for the substitutions may be attributed to errors in the calculated proton affinities in vacuum that do not cancel for substitutions involving groups with very different chemical properties.