Theoretical prediction of pKa values of seleninic, selenenic, sulfinic, and carboxylic acids by quantum-chemical methods.
Aqueous acid dissociation constants of substituted areneseleninic, areneselenenic, arenesulfinic, and benzoic acids are calculated by ab initio (MP2) and DFT (B3LYP) methods in combination with bulk solvation models (IEFPCM, CRSrad) from appropriate thermodynamic cycles. Mean absolute deviations (MAD) between experimental and calculated pK(a) values are quite large for basis sets without diffuse functions; however, trends are reasonably well described. Best agreement with experiment as described by MAD as well as correlation coefficient and slope of the correlation equation pK(a) = a*ΔG(calc)/RT ln(10) + b is obtained with the CPCM solvation model using the defaults optimized within COSMO-RS (CRSrad; MAD = 1.54, R(2) = 0.94, a = 0.83). Sulfenic (selenenic) acid tautomers are significantly more stable than the corresponding sulfoxide (selenoxide) forms.
Institut für Chemie, Karl Franzens Universität Graz, Heinrichstrasse 28, A-8010 Graz, Austria. ali.syed-tahir@edu.unigraz.at
S Tahir
ST
Ali
Sajjad
S
Karamat
Juraj
J
Kóňa
Walter M F
WM
Fabian
D001565:Benzoates / Q000737:chemistry; D002264:Carboxylic Acids / Q000737:chemistry*; D002621:Chemistry / Q000379:methods*; D005740:Gases; D006863:Hydrogen-Ion Concentration; D008956:Models, Chemical; D015233:Models, Statistical; D016566:Organoselenium Compounds / Q000737:chemistry*; D011789:Quantum Theory; D012997:Solvents / Q000737:chemistry; D013434:Sulfenic Acids / Q000737:chemistry*; D013441:Sulfinic Acids / Q000737:chemistry*; D013816:Thermodynamics
D001565:Benzoates; D002264:Carboxylic Acids; D005740:Gases; D016566:Organoselenium Compounds; D012997:Solvents; D013434:Sulfenic Acids; D013441:Sulfinic Acids; C473453:seleninic acid