Naslov
Vibrational study of different polymorphs of glycolaldehyde

Autori
Mohaček Grošev, Vlasta ; Ivanković, Hrvoje

Vrsta, podvrsta i kategorija rada
Sažeci sa skupova, sažetak, znanstveni

Izvornik
Book of abstracts / Handke, Miroslaw ; Hasik, Magdalena ; Paluszkiewicz, Czeslawa - Krakov : Wydawnictwo naukowe, 2004, 167-167

Skup
XXVII European congress on molecular spectroscopy

Mjesto i datum
Kraków, Poljska, 04.09.2004. - 11.09.2004

Vrsta sudjelovanja
Poster

Vrsta recenzije
Međunarodna recenzija

Ključne riječi
Raman; infrared; glycolaldehyde; crystal structure; phase transition

Sažetak
Glycolaldehyde (purchased from Fluka, purity better than 99 %) at room temperature exists in the form of a dimer: 2, 5-dihydroxy-1, 4-dioxane. Two crystalline phases were first identified by Kobayashi et al. [1] by means of infrared and Raman spectra, and the assignment was tentative. Here the assignment of the spectra of two crystalline phases is presented and supported by normal coordinate analysis of dioxane and glyceraldehyde as well. Both dioxane and glyceraldehyde crystallize in the P21/n with Z=2 space group, and their low frequency Raman spectra dixplay six phonons below 150 cm-1. Comparing these spectra with low frequency Raman spectra of glycolaldehyde obtained in the 10 K - 300 K temperature interval, it seems plausible that the glycolaldehyde phase b is probably also from the P21/n class, with Z=2. On the other hand, the situation with the phase a is more complex: at 10 K there are as many as 18 phonons observed in low frequency Raman spectra. This would probably correspond better to the case Z=4, and due to bands overlap, only five bands seem to appear in the Raman spectrum at 295 K. Differential scanning calorimetry was employed in the study of glycolaldehyde polymorphs, and it happens that only one melting curve seems to be observed , even when different heating rates are used (2 K/min, 5 K/min and 15 K/min). X-ray diffractograms of powder samples a and b, on the other hand, show pronounced differences. 1. Y. Kobayashi, H. Takahara, H. Takahashi, K. Higasi, J. Mol. Struct. 32 (1976) 235.

Izvorni jezik
Engleski

Znanstvena područja
Fizika, Kemijsko inženjerstvo

POVEZANOST RADA