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Discrimination in resolving systems: Ephedrine‐mandelic acid
Author(s) -
Valente Edward J.,
Zubkowski Jeffrey,
Eggleston Drake S.
Publication year - 1992
Publication title -
chirality
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.43
H-Index - 77
eISSN - 1520-636X
pISSN - 0899-0042
DOI - 10.1002/chir.530040807
Subject(s) - chemistry , monoclinic crystal system , salt (chemistry) , protonation , diastereomer , crystallography , hydrogen bond , crystal structure , carboxylate , ephedrine , stereochemistry , salt bridge , ion , molecule , organic chemistry , neuroscience , gene , biology , biochemistry , mutant
Resolution of mandelic acid with (—)‐(1R,2S)‐ephedrine in water and ethanol produces intermediate diastereomeric salts with greatly disparate solubilities and melting points. Single crystal X‐ray analysis of the less (L) and more (M) soluble (—)‐ephedrinium mandelates ( I, II ) shows crystal structures which are isosteric, each crystallizing in the monoclinic system, space group C 2. Protonated ephedrines occupy the same relative positions in the L‐ and M‐salts, and mandelates are in the same general locations. Hydrogen bonds link alternating protonated ephedrine nitrogens and mandelate carboxylate oxygens in each salt forming columns of ions. The helical H‐bonded chain winds down the crystallographic 2‐fold screw axis. Additional H‐bonds form between 2‐fold related mandelates in the L‐salt. Mixed crystals, containing both mandelate isomers, (2R)‐ and (2S)‐mandelates, are obtained from the resolving system partly depleted of the L‐salt. A specimen with nearly equal amounts of the mandelates ( III ) is also isosteric with the commensurate structures. I (294K), L‐salt: a = 18.160(7), b = 6.538(2), c = 13.898(4) Å, β = 92.02(3)°, V = 1649.1(9) Å 3 ; IIa (294K), M‐salt: a = 17.978(11), b = 7.164(4), c = 13.574(6)Å, β = 96.41(4)°, V = 1737.3(16) Å 3 ; IIb (223K), M‐salt: a = 17.805(8), b = 7.115(2), c = 13.50(5) Å, β = 96.89(3)°, V = 1697.9(15) Å 3 ; III (294K), mixed‐salt: a = 18.184(22), b = 6.792(7), c = 13.808(19) Å, β = 93.74(10)°, V = 1701.7(35) Å 3 . © 1992 Wiley‐Liss, Inc.