Amoxicillin trihydrate, a crystalline form of the antibiotic amoxicillin, possesses distinct chemical properties crucial for its pharmaceutical applications. Its molecular formula is C16H19N3O5S·3H2O, reflecting the inclusion of three water molecules within its structure. This trihydrate form exhibits a higher stability compared to the anhydrous form, making it preferable for storage and formulation.
Molecular Structure and Conformation
Amoxicillin trihydrate features a β-lactam ring, a crucial structural element responsible for its antibacterial activity. This ring is fused to a thiazolidine ring, and the molecule also includes a p-hydroxyphenyl group. The stereochemistry of the molecule, specifically the configuration of the chiral centers, is critical. Amoxicillin exists as a mixture of diastereomers, with the S-configuration at the α-amino acid carbon being the pharmacologically active form. The trihydrate form’s crystal structure incorporates three water molecules involved in hydrogen bonding within the crystal lattice, influencing its physical properties.
Physical Properties
- Appearance: White or almost white crystalline powder. Solubility: Freely soluble in water, sparingly soluble in methanol, slightly soluble in ethanol, practically insoluble in chloroform and ether. Melting Point: The melting point is affected by the rate of heating, decomposition typically occurs above 190 °C. Hygroscopy: Absorbs moisture from the air. Optical rotation: Exhibits a specific optical rotation.
Analytical Characteristics
Infrared (IR) Spectroscopy: Provides a unique fingerprint of the molecule, allowing identification and purity assessment. Nuclear Magnetic Resonance (NMR) Spectroscopy: Confirms the molecular structure and purity by providing detailed information on the chemical environment of different atoms in the molecule. High-Performance Liquid Chromatography (HPLC): Ensures purity and quantitation of amoxicillin trihydrate CRS. Water Content Determination: Karl Fischer titration measures the amount of water incorporated in the trihydrate crystal structure.
Stability Considerations
Amoxicillin trihydrate CRS is susceptible to hydrolysis in solution and degradation under certain conditions (temperature and pH). Proper storage conditions (cool and dry environment) are vital to maintain its stability and potency.
