Theoretical study of hydrogen-bonded complexes of chlorophenols with water or ammonia: Correlations and predictions of pKa values.
A simple practical method for predicting the acidity constants (as pKa values) of chlorophenols is proposed based on density functional theory calculations of a series of hydrogen-bonded complexes of phenol and 19 different congeners of chlorophenol, with a single probe molecule, either water or ammonia. Relevant structural parameters and molecular properties of these complexes, primarily involving the acidic hydroxyl group, are examined and plotted against the known pKa values of 14 chlorophenols and phenol. Strong linear correlations are found for these compounds. Such correlations are used to determine the pKa values of five chlorophenols whose experimental acidities have large uncertainties. Similar predicted pKa values are obtained by using different structural parameters and molecular properties for the complexes with either probe molecule. The study may be extended to determine the acidity of other compounds with a single acidic functional group.
Han
Jun
J
Department of Chemistry and Biochemistry, California State University, Fullerton, California 92834.
Deming
Richard L
RL
Tao
Fu-Ming
FM
D000465:Algorithms; D000641:Ammonia / Q000737:chemistry*; D002733:Chlorophenols / Q000737:chemistry*; D006860:Hydrogen Bonding; D006863:Hydrogen-Ion Concentration; D008956:Models, Chemical; D013816:Thermodynamics; D014867:Water / Q000737:chemistry*
D002733:Chlorophenols; D014867:Water; D000641:Ammonia