Linda Seton Flashcards
What is a crystal?
A solid with a regular pattern in which molecules/atoms/ions are arranged
What is a polymorph?
Different structural (pattern) arrangement of the same molecule/atom/ion
The process of crystallisation is important in the manufacture of medicines. What is it used for?
Purify and separate the active pharmaceutical ingredient from the other components like fillers, contaminants etc
What two phases can crystallisation occur in?
Nucleation phase
Crystal growth phase
List some key features of paracetamol?
Not spherical - planar
IMF - hydrogen bonds
What is a crystal structure?
Arrangement of molecules within a solid crystal
What is an amorphous solid?
A solid which does not have long range order - glass
Give two examples in the past of the importance of polymorphs for pharmaceutical companies?
Ritanovir - Abbot - started to fail solubility tests - new polymorph of drug discovered
Zantac - Glaxo - tried to patent second polymorph later sued by Novapharm
What is the metastable zone?
Composition is within the supersaturated region but nucleation is slow
What is the labile region?
Where nucleation is spontaneous and crystal growth is rapid
What is the driving force of nucleation and crystal growth?
Supersaturation
What is nucleation?
Molecules in solution join together and form clusters
What is the critical cluster or critical nucleus?
When the clusters formed by nucleation are at a size were they are stable and will not break up
What will happen to a cluster if: 2 < critical size?
The cluster will break up
What will happen to a cluster if: 2 > critical size?
The cluster will not break up as it is stable
