L-Histidine Methyl Ester Dihydrochloride

Abstract

The title compound, C7H13N3022+.2C1 -, has distances and angles quite similar to those of histidine hydrochloride monohydrate [Donohue & Caron (1964). Acta Cryst. 17, 1178Cryst. 17, -1180, except for the distances within the ester functionality. Am. Chem. Soc. 94,8212. Frisch, M. J., Head-Gordon, M., Trucks, G. W., Foresman, J., Schlegel, H., Raghavachari, K., Robb, M. S., Binkley, J. S., Gonzalez, C., Defrees, D. J., Fox, D. J., Whiteside, R. A., Seeger, R., Melius, C. F., Baker, J., Martin, R. L., Kahn, L. R., Stewart, J. J. P., Topiol, S. & Pople, J. A. (1992). GAUSSIAN92. Gaussian Inc., Pittsburgh, PA, USA. Gao, Q., Sood, A., Shaw, B. R. & Williams, L. D. (1996). Acta Cryst.C52. In the press. Johnson, C. K. (1965 11 mmol) were refluxed for 8 h in 300 ml of tetrahydrofuran. The mixture was allowed to cool. The resulting solids were collected by vacuum filtration and recrystallized from water. Symmetry codes: (i) 1 + x, y, z; (ii) 1 -x, y -½, -1 -z. Crystal dataThe absolute configuration was fixed by the use of L-histidine in the 'synthesis'. Inversion of the structure and refinement of the D configuration gave a slightly poorer agreement (R = 0.0329, wR = 0.0346 and S = 1.88). Data collection: MSC/AFC Diffractometer Control Software (Molecular Structure Corporation, 1988 We are grateful to the Kresge Foundation for providing the funds for the purchase of the diffractometer used in this work.

Binary diffusion coefficients of l-histidine methyl ester dihydrochloride in aqueous solutions

“…We have determined this from DFT calculations as a starting point to characterize the species present in solution. Figure 2 shows the DFT optimized structure of L-HMEDH considering the bulk solvent effects of water through the polarizable continuum model (PCM), while table 4 summarizes selected structural parameters from this calculation and the reported X-ray structure [31]. The agreement between calculated and experimental values is, generally, good, and the maximum interatomic distance in the optimized structure of the L-HMEDH in solution is 0.960 nm, indicating a fully extended conformation.…”

“…The crystal structure of L-HMEDH has been reported from X-ray diffraction studies [31]. We have determined this from DFT calculations as a starting point to characterize the species present in solution.…”

“…For this, we assume that the diffusion of this amino acid ester is treated as the diffusion of the ''strong 2:1 electrolyte'' consisting of L-HME 2+ ions and Cl À ions. [31,49], from which for the compositions studied, the degree of dissociation is always less than 3% [31]. Thus, from our measurements of diffusion coefficients, D, (table 2) and considering equation (3), we have estimated the thermodynamic factor values for different concentrations (table 3).…”

“…While we are not sure of the reason for this, it does not affect the overall description. In the crystal, the overall structure, including locations of chloride ions, is suggested to arise from a network of hydrogen bonds [31]. In water, these interactions are diminished by solvation and the L-HME 2+ dication and chloride anions will be largely dissociated.…”

“…Diffusion coefficients of some amino acids have previously been reported for aqueous solutions at T = 298.15 K over the concentration range from (0.001 to 0.100) mol Á dm À3 , using measurement by various techniques [12][13][14][15][16][17][18][19][20][21][22][23][24][25][26][27][28][29][30]. We concentrate on the important model system of L-histidine methyl ester (as its dihydrochloride, L-HMEDH [31]), for which, as far as the authors know, no data on mutual diffusion coefficients have been published. We report the inter-diffusion coefficients at T = 298.15 K of aqueous L-HMEDH, over the concentration range from (0.001 to 0.100) mol Á dm À3 .…”