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Two new paracetamol/dioxane solvates--a system exhibiting a reversible solid-state phase transformation.
Ranko M Vrcelj1, Nathan I B Clark, Alan R Kennedy
1Department of Pure and Applied Chemistry, University of Strathclyde, Thomas Graham Building, 295 Cathedral Street, Glasgow, G1 1XL, UK. rmv22@cam.ac.uk
Journal of Pharmaceutical Sciences
|September 23, 2003
Summary
This study reveals two distinct crystalline forms (polymorphs) of paracetamol dioxane solvates. These forms interconvert reversibly, with desolvation yielding the stable monoclinic paracetamol phase.
Area of Science:
- Crystallography
- Solid-state chemistry
- Materials science
Background:
- Paracetamol is a widely used analgesic and antipyretic.
- Understanding paracetamol's solid-state forms is crucial for drug formulation and stability.
- Polymorphism in pharmaceuticals can significantly impact bioavailability and therapeutic efficacy.
Purpose of the Study:
- To elucidate the crystal structures of two dioxane solvates of paracetamol.
- To investigate the structural relationship and phase transformation between these solvates.
- To determine the outcome of desolvation on the paracetamol crystal structure.
Main Methods:
- Single-crystal X-ray diffraction was employed to determine the crystal structures.
- Variable temperature studies were conducted to observe phase transformations.
- Structural analysis was performed to understand intermolecular interactions and packing.
Main Results:
- Two true polymorphs of paracetamol dioxane solvates were identified: a high-temperature orthorhombic form (Pbca) and a low-temperature monoclinic form (P21/c).
- Detailed crystal structure data, including lattice parameters and space groups, were determined for both forms at different temperatures.
- A reversible phase transformation between the two solvate forms was observed.
- Desolvation of either solvate form was found to yield the stable monoclinic phase of paracetamol.
Conclusions:
- The study successfully characterized two novel paracetamol polymorphs, providing detailed structural insights.
- The reversible phase transformation highlights the dynamic nature of paracetamol solvates.
- Desolvation leading to the stable monoclinic phase is a key finding for pharmaceutical processing and storage.