Heat-capacity changes and partial molal heat capacities of several amino acids in water

Prasad, K. P. ; Ahluwalia, J. C. (1976) Heat-capacity changes and partial molal heat capacities of several amino acids in water Journal of Solution Chemistry, 5 (7). pp. 491-507. ISSN 0095-9782

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Official URL: http://www.springerlink.com/content/j62j4331575642...

Related URL: http://dx.doi.org/10.1007/BF00650466


Integral enthalpies of solution of several amino acids in water at low concentrations have been determined at 25 and 35°C. These data have been used to derive the heat-capacity change ΔC p o on dissolution at 30°C. Partial molal heat capacities C p2°have been obtained by combining ΔC p° with C p2° (heat capacity of pure solid amino acids). The results indicate that the increments in ΔC p° and C p2° values per CH2 group increment in the homologous series of α-amino acids are constant and in agreement with those found for other homologous series of compounds containing monofunctional groups. However, this is not the case with amino acids having the NH 3 + group at the terminal position. The present work also indicates that, as the NH 3 + group is shifted away from the COO group, hydrophobic hydration decreases, as indicated by a decrease in ΔC p° and C p2° . The results on various isomers of amino acids show that branching of alkyl groups has no effect on ΔC p° and C p2° , indicating that hydrophobic hydration is unaffected by branching. The effect of substitution of H by OH and of CH3 by CH2-CO-NH2groups in some amino acids has also been studied and discussed.

Item Type:Article
Source:Copyright of this article belongs to Springer-Verlag.
Keywords:Enthalpies of Solution; Heat Capacity; Partial Molal Heat Capacity; Amino Acids; Hydrophobic Hydration
ID Code:299
Deposited On:20 Sep 2010 08:40
Last Modified:11 May 2011 07:25

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