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Questions and Answers
Which term describes crystals that contain solvent of crystallization?
What is the molar equivalent of water in a dihydrate?
Which type of crystal solvate is stable and difficult to desolvate?
What is the term used for a crystal structure that does not contain any water?
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When crystals lose their incorporated water and recrystallize in a new form, they are termed as:
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What distinguishes pseudopolymorphic solvates from true polymorphs?
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How does the presence of solvent affect the crystal lattice in pseudopolymorphic solvates?
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How do anhydrate crystals compare to hydrate crystals in terms of melting point?
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What can contribute to a slower dissolution rate in some hydrates compared to anhydrous forms?
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What is the purpose of forming pharmaceutical co-crystals?
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Why might there be measurable differences in bioavailability between different crystal forms of a drug?
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What is a characteristic feature of pseudopolymorphic solvates?
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How does the presence of impurities affect the formation of polymorphs?
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How do different polymorphic forms of a compound affect its drug development program?
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Which factor is NOT considered as a variable pertaining to the crystallization process in the formation of polymorphs?
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What distinguishes solvates (hydrates) from other types of crystalline solids?
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Which statement best describes the relationship between anhydrate forms and polymorphs?
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Study Notes
Crystal Classification
- Crystals containing solvent of crystallization are known as solvates or hydrates (when specifically involving water).
- In a dihydrate, the molar equivalent of water is two moles of water per mole of the solid.
- Stable solvates that are difficult to desolvate tend to be termed as "hydrates."
Crystal Structures
- An anhydrous crystal structure refers to a crystal that does not contain any water.
- When crystals lose incorporated water and recrystallize in a new form, they are referred to as "rehydrated" crystals.
Pseudopolymorphic Solvates
- Pseudopolymorphic solvates differ from true polymorphs in that they contain additional solvent molecules, affecting their crystal structure.
- The presence of solvent in pseudopolymorphic solvates can alter the arrangement of the crystal lattice, leading to variations in stability and solubility.
Melting Points and Dissolution Rates
- Anhydrate crystals generally exhibit higher melting points than their hydrate counterparts due to stronger intermolecular forces.
- Some hydrates may display slower dissolution rates than their anhydrous forms due to their structural integrity and bonding with water molecules.
Pharmaceutical Applications
- The purpose of forming pharmaceutical co-crystals is to enhance the solubility and stability of active pharmaceutical ingredients, improving their bioavailability.
- Differences in bioavailability among various crystal forms of a drug can arise from factors such as solubility, dissolution rates, and stability.
Polymorphism Characteristics
- A defining feature of pseudopolymorphic solvates is their distinct physical and chemical properties, influenced directly by the presence of solvent.
- Impurities can play a significant role in the formation of polymorphs by disrupting the crystallization process and leading to diverse crystal habits.
Drug Development Impact
- Variations in polymorphic forms of a compound can greatly influence a drug development program, affecting formulation strategies, quality control, and regulatory considerations.
- A factor not considered a variable in crystallization pertaining to the formation of polymorphs might include intrinsic properties specific to a compound.
Comparison of Solvates
- Solvates (hydrates) are distinguished from other types of crystalline solids by their incorporation of solvent molecules into the crystal lattice.
- Anhydrate forms and polymorphs are related in that different polymorphic forms can exist in both hydrated and anhydrous states, affecting their physical characteristics.
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Description
Explore the concept of pseudopolymorphic solvates, where the solvent is not part of the crystal bonding but occupies voids in the crystal. Understand how solvated forms of a drug differ in physicochemical properties and pharmaceutical behavior compared to the anhydrous form.
