Binary diffusion coefficients of l-histidine methyl ester dihydrochloride in aqueous solutions |
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| Affiliation: | 1. U.D. Química Física, Facultad de Farmacia, Universidad de Alcalá, 28871 Alcalá de Henares, Madrid, Spain;2. Coimbra Chemistry Centre, Department of Chemistry, University of Coimbra, 3004-535 Coimbra, Portugal;1. Chemistry Department, Faculty of Science-North Jeddah, King Abdulaziz University, Saudi Arabia;2. Chemistry Department, Faculty of Science, Assiut University, 71516 Assiut, Egypt;3. Chemistry Department, Faculty of Science, King Abdulaziz University, Saudi Arabia;1. Instituto de Investigaciones en Fisicoquímica de Córdoba (INFIQC, CONICET), Dpto. Química Orgánica, Fac. Ciencias Químicas, Universidad Nacional de Córdoba, Córdoba, X5000HUA, Argentina;2. Unidad de Investigación y Desarrollo en Tecnología Farmacéutica (UNITEFA, CONICET), Dpto. Farmacia, Fac. Ciencias Químicas, Universidad Nacional de Córdoba, Córdoba, X5000HUA, Argentina;1. Advanced Computing Research Laboratory, Institute of Computing Technology, Chinese Academy of Sciences, China;2. Beijing Key Laboratory of Mobile Computing and Pervasive Device, China;3. University of Chinese Academy of Sciences, China;4. University of Texas at San Antonio, United States;1. Division of Periodontology and Endodontology, Tohoku University Graduate School of Dentistry, 4-1 Seiryo-machi, Aoba-ku, Sendai 980-8575, Miyagi, Japan;2. Endodontics Department of Dental College, Jazan University, Saudi Arabia |
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| Abstract: | The Taylor dispersion technique has been used for measuring mutual diffusion coefficients of l-histidine methyl ester as its dihydrochloride at T = 298.15 K and finite concentrations from (0.001 to 0.100) mol · dm−3. On the basis of experimental mutual diffusion coefficients, the hydrodynamic radii, Rh, the diffusion coefficient at infinite dilution D0 and the dependence of thermodynamic factors, FT, on the concentration, have been estimated using the Onsager–Fuoss equation. Further insight on the diffusion has been obtained from 1H and 13C NMR spectroscopy and DFT calculations, which suggest that the l-histidine methyl ester is present as its dication in acidic solution in a fully extended conformation, with considerable charge delocalization over the imidazolium ring. These experimental and computational results allow us to have a better understanding of the thermodynamic and kinetic behavior of this amino acid derivative in aqueous solutions. |
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| Keywords: | Diffusion coefficient Amino acids Aqueous solutions Taylor dispersion NMR DFT |
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