Experimental Investigation On Thermodynamic Properties Of Sugar Alcohols And Amino Acids In Vitamin Aqueous Solution

Amino acids and vitamins are necessary bioactive substances to thegrowth and development of all kinds of creatures. Functional sugaralcohols are beneficial to Yhe b d^'X metabolism. In vivo, water may beYhe XY\ide^ZXed X [e Y dZe Y iYX aWge c Ye Y. TheWef We, iY'X ftremendous significance to study the th ermodynamic properties of thesebioactive substances in aqueous solutions, which could also provide agreat deal of information for many fields, such as food, pharmacy,chemical engineering and so forth.In this work, a vibrating tube density meter DMA4500M ?AntonPaar, Austria? and an Ivisc Ubbelohde capillary viscometer ?Lauda,Germany? have been applied respectively to measure the densities andviscosities of sugar alcohols ?erythritol/xylitol/mannitol/sorbitol/maltitol? and amino acids ?glycine/L-alanine/L-valine/L-threonine/L-arginine? in ?0.0to0.4? mol·kg^-1L-ascorbic acid aqueous solutions,and these amino acids in ?0.1to0.4? mol·kg^-1vitamin B6acid aqueoussolutions, at T=?293.15,303.15,313.15and323.15? K underatmospheric pressure. Based on the experimental data, Guimar esequation and extended Jones-Dole equation were employed to correlatethe densities and viscosities of solutions, respectively. The apparentmolar volumes ?V_??, the limiting partial molar volumes ?V_?⁰? and thelimiting partial molar volumes of tra XfeW (?_trV_?⁰), the limiting partialmolar expansibilities ?E₂⁰? and Hepler parameters were calculatedthrough densities. Meanwhile, The viscosity B coefficients and the freeenergies of activation per mole of solvent (??₁^0?) and solute (??₂^0?) wereobtained through the viscosities. Then, the effect of temperature andconcentration on these volumetric and viscometric properties and thesolute solvation were discussed in terms of their molecular interactionsand structures.The limiting partial molar volumes ?V_?⁰? and viscosity B-coefficients were split into contributions from zwitterionic end group ?NH₃⁺, COO^-?and CH₂group. The contributions of ?NH₃⁺, COO^-?, CH, CH₂, CH₃, OH,CNHNHNH₂to V_?⁰and B-coefficients were calculated. The results showthat they all contribute positively to V_?⁰and viscosity B-coefficients andincrease with the molality of L-ascorbic acid or vitamin B6aqueoussolutions.