Article

Crystal growth of α and γ glycine polymorphs and their polymorphic phase transformations

Journal of Crystal Growth (Impact Factor: 1.69). 12/2008; 311(1):156-162. DOI: 10.1016/j.jcrysgro.2008.10.084

ABSTRACT The single crystals of α and γ polymorphs of glycine were grown from aqueous solutions at ambient conditions. The metastable α-form was crystallized from pure aqueous solution and the stable γ-form from aqueous solution in the presence of a critical concentration of a selective additive sodium chloride. Attempt to grow sizable β-form single crystals were not successful because of their high instability. In stability terms at ambient conditions these three glycine polymorphs are like this: β

0 Followers
 · 
108 Views
  • [Show abstract] [Hide abstract]
    ABSTRACT: Glycine is the simplest achiral amino acid that undergoes spontaneous mirror symmetry breaking when it crystallizes in its chiral γ-polymorphic modification. As a result of Ostwald ripening, its racemic mixture stochastically becomes optically active. The sense of the resulting handedness can be controlled by addition of one enantiomer of a simple chiral amino acid, the alanine.
    CrystEngComm 01/2015; 17:1513 - 1517. DOI:10.1039/C4CE02434F · 3.86 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Proton dissociation assisted negative polarity of malonic acid molecules admist glycine zwitterions leads to orgination of γ nucleation in the solution. Alteration in the nucleation behaviour and segregation of glycine polymorphs in the presence of malonic acid over a wide range of concentrations has been investigated both by experimental and analytical approaches. Complete changeover in the nucleation behaviour from 100% α to 100% γ is observed at the critical concentration of the additive. Shifting in the overall charge environment of the system towards cationic in the presence of malonic acid favours the nucleation of γ through induced charge compensation in the solution. Tuning of merohedral twinning in γ nucleation by the additive concentration has been well revealed in the present work. CNT based analytical approach employed elucidates well the experimental observations through the estimated interfacial energy, volume excess free energy, critical radius, activation energy barrier and nucleation rates of α and γ polymorphs. Structural affirmation of the nucleated polymorphs was carried out by powder x-ray diffraction.
    Crystal Research and Technology 02/2015; 50(2). DOI:10.1002/crat.201400400 · 1.16 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: In glycine crystal the transformation from γ to α modification has been investigated using differential scanning calorimetry (DSC) and low-frequency dielectric spectroscopy methods on powder and monocrystalline samples. In monocrystalline samples the transition begins at 457.5 K. The first step is connected with cracking of the sample and growing of the ac conductivity which reaches maximum at 458.5 K. Next, ac conductivity achieves a huge maximum at the transition point 462.8 K. Additional small anomaly in the complex dielectric constant was revealed at 335 K. In powder samples this transformation measured by the DSC method goes uniformly. For these samples the ac conductivity begins to grow rapidly from 455 K and grows 2.5 times in the range of 383–387 K. In powder samples the ac conductivity at the transition point is seven times greater than in the monocrystalline samples. Conductivity anomalies are accompanied by changes in the real part of the dielectric constant.
    Phase Transitions 11/2014; 87(10-11). DOI:10.1080/01411594.2014.953951 · 1.04 Impact Factor