Some thermodynamic parameters for hydroxy amino acids: Bicine and tricine

✍ Scribed by M. L. Soni; R. C. Kapoor

• Book ID: 104580358
• Publisher: John Wiley and Sons
• Year: 1981
• Tongue: English
• Weight: 255 KB
• Volume: 20
• Category: Article
• ISSN: 0020-7608
• DOI: 10.1002/qua.560200211

✦ Synopsis

Abstract

pK values of N,N‐dihydroxyethylglycine (bicine) and N‐[tris(hydroxymethyl)methyl]‐glycine (tricine) have been determined by the Irving‐Rossotti method in an aqueous medium at 25, 30, 35, 40, 45, and 50°C and at different ionic strengths (I = 0.1, 0.5, and 1.0). Plots between pK~a~(NH) and 1/T for various ionic strengths have been obtained and the values of slopes have been used to calculate the Δ__H__, Δ__S__, and Δ__G__ for the dissociation reactions of bicine and tricine. The Δ__H__, Δ__S__, and Δ__G__ values for bicine were found to be 10.6 ± 0.6 kcal mol^−1^, −1.9 ± 1.8 e.u., and 11.1 ± 0.06 kcal mol^−1^, respectively, and for tricine 11.2 ± 0.6 kcal mol^−1^, 1.6 ± 1.6 e.u., and 10.7 ± 0.06 kcal mol^−1^, respectively. The pK~a~(NH) values decrease with rise in temperature but the influence of ionic strength is not significant.