(R)-mandelic acid (S)-alanine hemihydrate

Area of Science:

• Crystallography
• Organic Chemistry
• Chemical Crystallography

Background:

• Chiral resolution is crucial for separating enantiomers.
• Mandelic acid is a common chiral compound used in resolution studies.
• Amino acids can act as resolving agents for chiral acids.

Purpose of the Study:

• To investigate the crystal structure of a complex formed between mandelic acid and (S)-alanine.
• To demonstrate the effectiveness of (S)-alanine in the optical separation of racemic mandelic acid.
• To analyze the hydrogen bonding interactions within the crystal structure.

Main Methods:

• Crystallization from an aqueous solution.
• Single-crystal X-ray diffraction analysis.
• Structural comparison of related compounds.

Main Results:

• The crystal structure of the complex C(3)H(7)NO(2).C(8)H(8)O(3).0.5H(2)O was determined.
• Successful optical separation of racemic mandelic acid was achieved, yielding (R)-mandelic acid and (S)-alanine in a 1:1 molar ratio.
• A strong hydrogen bond with a short O...O separation (2.494 Å) was observed between carboxyl and carboxylate groups.
• Structural analysis indicated that this strong hydrogen bonding impacts neighboring covalent bonds.

Conclusions:

• The co-crystallization of (S)-alanine with racemic mandelic acid is an effective method for chiral resolution.
• The observed hydrogen bonding network plays a significant role in the crystal packing and stability.
• The study provides insights into the structure-property relationships influenced by intermolecular interactions.