0438343 - FZÚ 2015 RIV US eng J - Článek v odborném periodiku
Wu, H. - Reeves-McLaren, N. - Pokorný, Jan - Yarwood, J. - West, A.R.
Polymorphism, phase transitions, and thermal stability of L-Pyroglutamic acid.
Crystal Growth & Design. Roč. 10, č. 7 (2010), s. 3141-3148. ISSN 1528-7483. E-ISSN 1528-7505
Výzkumný záměr: CEZ:AV0Z10100520
Klíčová slova: nonlinear-optical crystal * asymmetric-synthesis * vibrational-spectra * parkinsons-disease
Kód oboru RIV: BM - Fyzika pevných látek a magnetismus
Impakt faktor: 4.390, rok: 2010 ; AIS: 0.992, rok: 2010
DOI: https://doi.org/10.1021/cg100260f

L-Pyroglutamic acid undergoes a phase transition, alpha-->beta, at similar to 68 degrees C on heating, which is reversible with hysteresis depending on the cooling rate, before melting at similar to 162 degrees C. On cooling, a further reversible transition, alpha-->alpha', which shows martensitic characteristics, occurs at similar to -140 degrees C. The structural changes at the transitions were studied by variable temperature X-ray powder diffraction and Raman spectroscopy and compared with reports of single crystal structure determinations. Differences in Raman spectra were attributed to differences in intermolecular N-H center dot center dot center dot O interactions in the three enantiotropic polymorphs. By optical microscopy, crystals frequently jumped around the microscope slide on passing through the alpha/beta transition; this is attributed to discontinuous changes in the unit cell dimensions leading to a spring effect in the crystals.
Trvalý link: http://hdl.handle.net/11104/0241763