Raman spectroscopic evidence of low temperature stability of D,L-glycolic and L-(+)-lactic acid crystals

Vlasta Mohaček-Grošev; Vladimir Šoštarić; Aleksandar Maksimović

doi:10.1016/j.saa.2014.12.048

Raman spectroscopic evidence of low temperature stability of D,L-glycolic and L-(+)-lactic acid crystals

Spectrochim Acta A Mol Biomol Spectrosc. 2015 Apr 5:140:35-43. doi: 10.1016/j.saa.2014.12.048. Epub 2014 Dec 30.

Authors

Vlasta Mohaček-Grošev¹, Vladimir Šoštarić², Aleksandar Maksimović³

Affiliations

¹ Ruđer Bošković Institute, Bijenička cesta 54, 10002 Zagreb, POB 180, Croatia. Electronic address: mohacek@irb.hr.
² Stupnička 14, 10000 Zagreb, Croatia.
³ Ruđer Bošković Institute, Bijenička cesta 54, 10002 Zagreb, POB 180, Croatia.

PMID: 25579800
DOI: 10.1016/j.saa.2014.12.048

Abstract

Raman and infrared spectra of polycrystalline D,L-glycolic and L-(+) lactic acid are presented and assigned both by an ab initio calculation of normal modes of free conformers and by self-consistent-charge density-functional-theory computational program DFTB+. Temperature dependent Raman spectra from 295 K to 10 K reveal great stability of crystal lattices, since no soft modes and no band splittings that could be attributed to changes of the number of molecules per unit cell were observed. A semiempirical calculation with GULP program was used to estimate the strength of hydrogen bonds in crystals: in glycolic acid they have energies of -0.337 eV/mol, -0.329 eV/mol, -0.262 eV/mol and -0.242 eV/mol, while in lactic acid two hydrogen bonds have energies of -0.283 eV/mol and -0.202 eV/mol.

Keywords: Biodegradable material; Glycolic acid; Lactic acid; Normal modes; Phonons; Temperature stability.

Publication types

Research Support, Non-U.S. Gov't

MeSH terms

Cold Temperature
Crystallization
Glycolates / chemistry*
Lactic Acid / chemistry*
Models, Molecular
Spectrum Analysis, Raman

Substances

Glycolates
glycolic acid
Lactic Acid