4067-90-7Relevant academic research and scientific papers
Reactions of Crystalline (R)-(-)- and (S)-(+)-Mandelic Acid with Amines. Crystal Structure and Dipole Moment of (S)-Mandelic Acid. A Method of Determining Absolute Configuration of Chiral Crystals
Patil, A. O.,Pennington, W. T.,Paul, I. C.,Curtin, D.Y.,Dykstra, C.E.
, p. 1529 - 1535 (1987)
The reactions of (+)-1-phenylethylamine vapor occurs more rapidly with single crystals of (+)-mandelic acid to form the (+)(+) or"p" salt than with (-)-mandelic acid to give the (+)(-) or "n" salt, known to be the less soluble on crystallization from solution.The reaction fails to show the anisotropy characteristic of some other reactions of crystalline acids with chiral gases.The crystal structure of (S)-(+)-mandelic acid has been determined.The structure is monoclinic, P2%, with a=8.629 (1) A, b=5.861 (1) A, c=15.185 (2) A, β=102.76 (1) deg, and Z=4.The structure was determined by direct methods and refined to R=0.035 for the 1347 reflections recorded with a single-crystal diffractometer.The dipole moments of the mandelic acid molecules in the conformations found in the crystal structure determination were calculated by an ab initio SCF method.These results, together with the crystal morphology and known absolute configuration of the crystal, can be used to determine the direction of the electric dipole of Single crystals of (S)-mandelic acid.The result is in agreement with the direction determined by spraying heated crystals with the powder mixture of Burker in the classic test for absence of a crystal center of symmetry.When the argument is inverted it provides a method for determining the absolute configuration of chiral, electrically polar molecules from the X-ray crystal structure, crystal morphology, and direction of the electric dipole of the crystal.The reaction of mandelic acid crystals with phenylethylamine vapor is discussed in terms of the crystal structure.A survey has been made of the solid-gas reactions of mandelic acid with ammonia, 2-butylamine, and tert-butylamine.
Chiral Discrimination in the Structures and Energetics of Association of Stereoisomeric Salts of Mandelic Acid with α-Phenethylamine, Ephedrine, and Pseudoephedrine
Zingg, S. P.,Arnett, Edward M.,McPhail, Andrew T.,Bothner-By, Aksel A.,Gilkerson, W. R.
, p. 1565 - 1580 (2007/10/02)
A careafully coordinated study of the relations between structure and energetics of association in the crystalline state and solution is reported here.Hydrogen-bonded ion pairs formed from reaction between the enantiomers of mandelic acid, α-phenethylamine, ephedrine, and pseudoephedrine have been studied in dimethyl sulfoxide, dioxane, and water and as solid salts.Single-crystal X-ray analysis, performed on four unique diastereomeric pairs of (+/-)-ephedrinium and (+/-)-pseudoephedrinium (+/-)-mandelates yielded details of the solid-state hydrogen-bonding schemes for all eight diastereomeric salts. 1H NMR spectra (at 300 and 600 MHz) over a wide concentration range were determined and indicated a simple two-state equilibrium between ion pairs and free ions in dimethyl sulfoxide.The dissociation equilibria in dimethyl sulfoxide were examined more quantitatively by conductance and the results treated by the Fuoss-Justice, Fuoss-1977, and Onsager methods to yield calculated dissociation constants, equivalent conductances, and mean activity coefficients over a wide concentration range.Thermochemical properties determined by various techniques were (1) the heat of fusion by differential scanning calorimetry, (2) heats of solution of the crystalline salts to high dilution by isoperibolic batch calorimetry, and (3) heats of protonation and heats of dissociation from thermometric titration of solutions of mandelic acid with the bases.Extensive use was made of cross-chiral checks (e.g., R,R' vs S,S') to prove that observed chiral discrimination factors were real and accurate.Significant chiral discrimination factors were found for all properties of diastereomeric combinations.In several cases the largest differences in thermochemical properties and 1H NMR spectra of diastereomeric pairs could be related reasonably to differences in hydrogen-bonding schemes in their crystals.
