Molecular interactions of cyclic hexaamine hydrochloride with dipeptides in aqueous solutions. Partial molar heat capacities and volumes of transfer of amine from water to aqueous dipeptide solutions

Abstract

Densities and specific heat capacities of binary and ternary aqueous systems containing N 6H 6·6HCl at concentration 0.06 mol·kg −1 and dipeptides: alanyl-alanine, threonyl-leucine, alanyl-glutamic acid, glycyl-tyrosine and alanyl-serine at concentration range 0.01 – 0.46 mol·kg −1 were determined by Anton Paar 60/602 digital densimeter and differential scanning adiabatic calorimeter DASM-4. The partial molar volumes and heat capacities of amine transfer from water to the dipeptide solution was determined as a function of dipeptide concentration. The variations of transfer partial molar volumes and heat capacities of cyclic amine in aqueous dipeptide solution as a function of dipeptide concentration have shown that stoichiometric complexes (amine/dipeptide) are present for the molar ratios: 1 3 for alanyl-alanine; 1 2.5 for threonyl-leucine; 1 2 for alanyl-glutamic acid; 1 1.5 for glycyl-tyrosine and 1 0.5 for alanyl-serine.