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

✍ Scribed by Rabindra N. Roy; Catherine P. Moore; Michael D. Bliss; Sunjeev Patel; Brian Benton; Julie A. Carlsten; William S. Good; Lakshmi N. Roy; Kathleen M. Kuhler

• Publisher: Elsevier Science
• Year: 1997
• Tongue: English
• Weight: 179 KB
• Volume: 29
• Category: Article
• ISSN: 0021-9614
• DOI: 10.1006/jcht.1997.0197

✦ Synopsis

The second dissociation constant pK2 values 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 from T = 278.15 K to T = 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, where m denotes molality, were used. The pK2 for 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.