Second dissociation constants of 3-(cyclohexylamino)-1-propanesulfonic acid (CAPS) and 3-(cyclohexylamino)-2-hydroxy-1-propanesulfonic acid (CAPSO) from the temperatures 278.15 K to 328.15 K

• Published in: The Journal of chemical thermodynamics Vol. 29; no. 7; pp. 749 - 756
• Main Authors: Roy, Rabindra N., Moore, Catherine P., Bliss, Michael D., Patel, Sunjeev, Benton, Brian, Carlsten, Julie A., Good, William S., Roy, Lakshmi N., Kuhler, Kathleen M.
• Format: Journal Article
• Language: English
• Published: Kidlington Elsevier Ltd 01.07.1997; Elsevier
• Subjects: activity coefficients; Chemical thermodynamics; Chemistry; dissociation; e.m.f; Elements, mineral and organic compounds; Exact sciences and technology; General and physical chemistry; Thermodynamic properties; thermodynamics; zwitterion; thermodynamics; activity coefficients; e.m.f; zwitterion; dissociation; Aminoalcohol; Cyclohexane derivatives; Hydroxyacid; Activity coefficient; Amino acids; Dissociation constant; Electromotive force; Chemical properties; Experimental study; Thermodynamic properties; Sulfonic acid; Organic compounds
• ISSN: 0021-9614; 1096-3626
• DOI: 10.1006/jcht.1997.0197

The second dissociation constant pK2values for 3-(cyclohexylamino)-1-propanesulfonic acid (CAPS) and 3-cyclohexylamino)-2-hydroxy-1-propanesulfonic acid (CAPSO), useful secondary standard buffers within the pH range of 9.7 to 10.5 for CAPS, and 8.9 to 10.0 for CAPSO, have been determined fromT=278.15 K toT=328.15 K. Electromotive force measurements of cells of the type: Pt·H2(g,p°=101.325 kPa)·buffer (m1) Na salt of buffer (m2), NaCl (m3)·AgCl·Ag, wheremdenotes molality, were used. The pK2for the ionization of CAPS in the experimental temperature range is expressed by the equation: pK2=1046.64·(K/T)+35.10191−4.9342·ln(T/K), whereas that for CAPSO is given by: pK2=2106.21·(K/T)+9.08772−1.11049·ln(T/K). The thermodynamic quantities have been calculated and the results obtained are compared with those for zwitterionic compounds which are the derivatives of taurine.