Effect of Temperature on The Solubility of α-Amino Acids and α,ω-Amino Acids in Water

The aqueous solubilities of glycine, dl-alpha-alanine (2-aminopropanoic acid), dl-alpha-aminobutyric acid (2-aminobutanoic acid), dl-alpha-norvaline (2-aminopentanoic acid), dl-alpha-norleucine (2-aminohexanoic acid), beta-alanine (3-aminopropanoic acid), gamma-aminobutyric acid (4-aminobutanoic acid), 5-aminovaleric acid (5-aminopentanoic acid), and 6-aminocaproic acid (6-aminohexanoic acid) were determined from 293.15 to 323.15 K at intervals of 5.00 K using the gravimetric method. The temperature dependence of the solubility of alpha-amino acids and alpha,omega-amino acids in water is well described by the van't Hoff equation. Linear van't Hoff plots were used to determine the differential enthalpy of solution. The results obtained are compared with reported values in literature and are discussed in terms of the position of the ionic groups in the hydrocarbon chain.