DL-alaninium semi-oxalate monohydrate

Area of Science:

• Crystallography
• Materials Science
• Chemical Physics

Background:

• The crystal structure of anhydrous DL-alaninium semi-oxalate has been previously characterized.
• Understanding the role of water molecules in crystalline structures is crucial for predicting material properties and transformations.

Purpose of the Study:

• To elucidate the crystal structure of hydrated L- and D-alaninium semi-oxalate.
• To investigate the impact of water molecules on crystal packing and hydrogen bonding networks.
• To compare the hydrated structure with its anhydrous counterpart.

Main Methods:

• Single-crystal X-ray diffraction was employed to determine the atomic arrangement.
• Comparative analysis of structural motifs and hydrogen bonding patterns between the hydrate and anhydrous forms.
• Investigation of dehydration behavior and phase transformation pathways.

Main Results:

• The hydrated structure (C(3)H(8)NO(2)(+)·C(2)HO(4)(-)·H(2)O) features L- and D-alaninium cations, semi-oxalate anions, and water molecules in a 1:1:1 ratio.
• Water molecules integrate into the hydrogen bond network, forming tetrahedral arrangements and causing geometric distortions compared to the anhydrous form.
• Short hydrogen bonds (O-H···O) are observed between semi-oxalate anions and between water and alaninium cations.

Conclusions:

• Water molecules significantly alter the crystal packing and hydrogen bonding in alaninium semi-oxalate.
• Dehydration of the hydrate yields a polycrystalline pseudomorph, indicating a complex transformation mechanism possibly involving a hemihydrate intermediate.
• The study highlights the subtle yet significant influence of hydration on crystalline material behavior.