The structure of (±)-malic acid, (±)-C4H6O5

Sluis, P. van der; Kroon, Jan

doi:10.1107/s0108270185006163

Cited by 15 publications

(14 citation statements)

References 7 publications

(9 reference statements)

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“…7,8 For L-malic acid only one crystal form was found, monoclinic, P2 1 C 2 2 ). 9 (The notations Cc, P2 1 and P2 1 /c are according to Refs.…”

Section: Resultsmentioning

confidence: 99%

“…In the˛-form of DL-malic acid crystals, the molecules are bound in a head-to-tail fashion, 7 whereas in theˇ-form they are bound in a head-tohead fashion. 8 In the crystals of L-malic acid the molecules are bound in a head-to-head fashion. 9 It has been established that DL-malic acid, used in our studies, crystallizes as theˇform (Z. Kubiak, personal communication), which means that L-and D-molecules are bound into dimers in a head-to-head fashion in the solid state.…”

Section: Resultsmentioning

confidence: 99%

See 1 more Smart Citation

Vibrational spectra of racemic and enantiomeric malic acids

Barańska¹,

Kuduk‐Jaworska

Szostak

et al. 2002

J Raman Spectroscopy

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The IR and Raman spectra of racemic (DL-) and both enantiomeric (L-and D-) forms of malic acids and also their silver salts and deuterated analogues were measured in the polycrystalline state in the range 4000-100 cm −1 . Significant differences in the spectra of the racemic and enantiomeric forms of malic acid were described for the first time and are discussed in relation to the structural features, including crystal symmetry, geometric parameter distinctions and hydrogen bonding. The most significant spectral differences were noted in the ranges 3000-2800 and 1740-1630 cm −1 . In the n(CH) stretching region distinctions were strongly pronounced in the Raman spectra and the observed pattern was ascribed to crystal symmetry differences. In the second region differences were visible in both the IR and Raman spectra and they were explained as a result of distinctions in the geometric properties of carboxyl-dimer rings of the L-and DL-forms, namely two non-equivalent types of H-bonded carboxyl-dimer rings are present in the crystal of DL-form, which results in a doublet in the n(C O) stretching region. In the case of the enantiomeric form, all H-bonded carboxyl-dimer rings are equivalent, so a single n(C O) band is observed in their spectra. Other differences in the spectra of these species were observed in the region below 1500 cm −1 but their explanation is less straightforward.

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“…7,8 For L-malic acid only one crystal form was found, monoclinic, P2 1 C 2 2 ). 9 (The notations Cc, P2 1 and P2 1 /c are according to Refs.…”

Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Vibrational spectra of racemic and enantiomeric malic acids

Barańska¹,

Kuduk‐Jaworska

Szostak

et al. 2002

J Raman Spectroscopy

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“…Until now two crystal modifications of the racemic compound have been encountered, whose structures have been solved by X-ray diffraction [ 1,2]. Mariano and Gil have carried out NMR measurements on the neutral and doubly charged species [ 31.…”

Section: Introductionmentioning

confidence: 99%

Conformational aspects of malic acid: A multidisciplinary approach

Stouten¹,

Leeflang²,

Eijck³

et al. 1988

Journal of Molecular Structure

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Malic acid molecules can adopt three different staggered conformations of minimum energy with respect to rotation around the central C-C bond: gauche -(g-), trans (t) and gauche + (g+ ). The conformational behaviour of the acid and of its dissociated forms has been studied by means of NMR experiments and Molecular Dynamics simulations and the results are compared with a statistical analysis of crystal structures and with Molecular Mechanics calculations.Specific coupling constants for all three ionization states were determined. Coupling constants of the three staggered rotamers were calculated and by comparison with the specific coupling constants of each ionization state rotamer populations were determined.Observed and calculated populations are similar, although the gauche + population resulting from the NMR experiment is significantly higher than predicted by the other methods. All techniques indicate that gauche + is the minor conformer of the neutral molecule. It is also shown that water-acid interactions play a very important role in describing the conformational behaviour of malic acid properly.

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“…At present, it is stated 33,35 that the phase diversity of this system includes the following discrete phases: enantiomers (S and R), equimolar racemic compounds of three modifications (RSI, RSII, and RSIII), and non-equimolar 1 : 3 and 3 : 1 stable (SR 3 and S 3 R) and metastable (1S3R and 3S1R) compounds. The crystal structures of the S-enantiomer, 41 racemates RSI 42 and RSII 43 and compound S 3 R are known. 35 Detailed specifications of all the phases are given in our highlight article published recently.…”

Section: Experimental Techniquesmentioning

confidence: 99%

Thermal deformations of crystal structures formed in the systems of malic acid enantiomers and l-valine–l-isoleucine enantiomers

2018

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The thermal behavior of discrete phases formed in the respective systems of malic acid enantiomers and L-enantiomers of the amino acids valine and isoleucine was studied using the temperature-resolved PXRD method. In the (S)-malic acid-(R)-malic acid system, thermal deformations in crystal structures of stable compounds (enantiomer S, racemates RSI and RSII, and non-equimolar compound S 3 R) and polymorph transformations of metastable compounds (racemate RSIII and non-equimolar compound 3S1R) were examined. In the L-valine-L-isoleucine system, thermal deformations in crystal structures of stable compounds L-Val and L-Ile and non-equimolar compound V 2 I were investigated. Thermal deformation analysis included plotting the temperature dependence of the unit cell parameters and volume, calculating thermal deformation tensors, plotting figures of thermal expansion coefficients (CTE), and estimating the extent of thermal deformation anisotropy. In all the cases studied, the maximal thermal expansion was observed in the direction of the weakest hydrogen (malic acid) or van der Waals (valine and isoleucine) intermolecular bonds, i.e. in the directions closest to that perpendicular to the dimer molecule chains (malic acid) or to molecular layers (valine and isoleucine). The strongest anisotropy of thermal deformations in monoclinic crystals was observed in the ac plane, in which the symmetrically unfixed angle β can vary.

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The structure of (±)-malic acid, (±)-C4H6O5

Cited by 15 publications

References 7 publications

Vibrational spectra of racemic and enantiomeric malic acids

Vibrational spectra of racemic and enantiomeric malic acids

Conformational aspects of malic acid: A multidisciplinary approach

Thermal deformations of crystal structures formed in the systems of malic acid enantiomers and l-valine–l-isoleucine enantiomers

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