caa a22 4500 469059117 CHVBK 20180323132852.0 cr unu---uuuuu 170328e19920101xx s 000 0 eng 10.1007/BF01053868 doi (NATIONALLICENCE)springer-10.1007/BF01053868 Evaluation of a direct1H NMR method for determining log K and Δ H values for crown ether -alkylammonium cation complexation [Elektronische Daten] [C. Zhu, J. Bradshaw, J. Oscarson, R. Izatt] A direct1H NMR method for determining logK and ΔH values for crown ether-ammonium cation complexation using milligrams of sample was tested and evaluated for accuracy and precision by comparing the results with those obtained using a titration calorimetric method. LogK values for the interactions of a non-chiral crown ether, diketopyridino-18-crown-6 (K2P18C6), with α-phenylethylammonium (PhEt+) perchlorate in 50%-50% and 90%-10% (v/v) mixtures of deuterated methanol (CD3OD) and deuterated chloroform (CDCl3) at four temperatures and, with α-(1-naphthyl)ethylammonium (NapEt+) perchlorate in 50%CD3OD-50%CDCl3 (v/v) at 25°C were determined by a direct1H NMR method. Values of ΔH for the interactions of K2P18C6 with PhEt+ in the two solvents were calculated from the temperature dependence of logK. LogK values for the interactions of a chiral crown ether, dimethyldiketopyridino-18-crown-6 (M2K2P18C6), with (R) and (S) enantiomers of NapEt+ in pure CD3OD at 25.0°C were also determined by the NMR method. The results were compared with those determined by a calorimetric method at 25.0°C in 50%-50% and 90%-10% (v/v) mixtures of plain methanol and chloroform, in 100% plain methanol, and in a 50%-50% mixture of partially deuterated methanol (with deuterium substitution on the methanol OH group, CH3OD) and deuterated chloroform. The log K values determined by both methods were found to be in good agreement, but the standard deviations associated with the NMR logK values were two to three times greater. The agreement of the ΔH values determined by the two methods was poor, differing by approximately 10 kJ/mol with the NMR method giving more negative values. The standard deviations associated with the NMR ΔH values were approximately ten times greater than those for the calorimetric values. Ion-pairing was observed for the interaction of perchlorate ion with both free and bound PhEt+ in 50%methanol-50%chloroform mixture. It is concluded that the NMR procedure is satisfactory for the determination of logK, but not ΔH values. Kluwer Academic Publishers, 1992 Crown ether-ammonium cation complexation nationallicence formation constants ( K ) and enthalpy changes (Δ H ) nationallicence direct1H NMR method nationallicence titration calorimetric method nationallicence Zhu C. Departments of Chemistry and Chemical Engineering, Brigham Young University, 84602, Provo, Utah, USA aut Bradshaw J. Departments of Chemistry and Chemical Engineering, Brigham Young University, 84602, Provo, Utah, USA aut Oscarson J. Departments of Chemistry and Chemical Engineering, Brigham Young University, 84602, Provo, Utah, USA aut Izatt R. Departments of Chemistry and Chemical Engineering, Brigham Young University, 84602, Provo, Utah, USA aut Journal of inclusion phenomena and molecular recognition in chemistry Kluwer Academic Publishers 12/1-4(1992-01-01), 275-289 0923-0750 12:1-4<275 1992 12 10847 https://doi.org/10.1007/BF01053868 text/html Onlinezugriff via DOI 1 research-article jats NATIONALLICENCE 856 40 https://doi.org/10.1007/BF01053868 text/html Onlinezugriff via DOI NATIONALLICENCE 700 1- Zhu C. Departments of Chemistry and Chemical Engineering, Brigham Young University, 84602, Provo, Utah, USA aut NATIONALLICENCE 700 1- Bradshaw J. Departments of Chemistry and Chemical Engineering, Brigham Young University, 84602, Provo, Utah, USA aut NATIONALLICENCE 700 1- Oscarson J. Departments of Chemistry and Chemical Engineering, Brigham Young University, 84602, Provo, Utah, USA aut NATIONALLICENCE 700 1- Izatt R. Departments of Chemistry and Chemical Engineering, Brigham Young University, 84602, Provo, Utah, USA aut NATIONALLICENCE 773 0- Journal of inclusion phenomena and molecular recognition in chemistry Kluwer Academic Publishers 12/1-4(1992-01-01), 275-289 0923-0750 12:1-4<275 1992 12 10847 Metadata rights reserved Springer special CC-BY-NC licence nationallicence BK010053 XK010053 XK010000 NATIONALLICENCE NATIONALLICENCE NL-springer