Preformulation Flashcards
what is a crystalline structure
a solid in which particles are arranged in a pattern that repeats periodically in 3D
What are the properties of a crystal
sharp melting points and are thermodynamically stable
What is a unit cell
The smallest repeating unit of a lattice
What is a lattice
A 3D set of points showing the position of the components that make a crystal
What are the 4 types of crystalline structure
salt, cocrystal, hydrate and solvate
What is a salt
a crystal made up of 2 or more ions including the API. Held together by ionic bonds
What is cocrystal
a crystal made up of 2 neutral molecules including the API held together by hydrogen bonds
What is a hydrate
a crystal made of water and the api
What is a solvate
A crystal made up of the api and a solvent that isn’t water
What are three common solvents used in solvates
Methanol, ethanol and acetone
What is polymorphism
when crystals have the same chemical composition but different internal structures
Why is polymorphism important
Means that different solids can have different physical properties such as melting point, solubility and bioavailability.
How do you analyse a crystals Structure
X ray
How do you analyse a crystal is thermal behaviour
Melting point and heat of fusion
How do you measure a crystals thermodynamic stability
Solubility, the more soluble the less stable
What is an amorphous crystal
A solid without a long range regular occurring 3D molecular pattern
What are the properties of amorphous solids
No sharp melting point and are thermodynamically unstable.
Which has a faster dissolution
Amorphous solids
Which is less stable
amorphous solids
What happens to amorphous solids when heated
They turn from glass like state to soft and rubbery because the molecules get enough energy to flow
What is the glass transition temperature
the temperature in which an amorphous solid turns from glass like to the soft rubbery state
What are the stages involved when amorphous solids are heated
first it drops when it reached the glass transition temperature then returns to its original level where it peaks again in which the solid crystallises and then drops dramatically when it reaches melting point.
What causes amorphous solids to turn into crystals
When kept on the shelf for too long. On form converts to another when thermodynamically favourable.
What is gibs free energy
a value that tells you if a reaction is favourable
What is the equation for the reaction of gibs free energy
ΔG= ΔH-S ΔS
How is the the molecular structure of solids analysed
using XRD, x ray diffraction
If ΔG is over 0 what does that mean
the reaction is thermodynamically unfavourable
If Δg is below 0 what does that mean
The reaction is thermodynamically favourable.
What is DSC
A way to measure how the physical properties of a sample change as the temperature changes
What is DSC used for
To analyse the change in phase of solid
What are emulsifiers
they’re substances that lower the surface tension between 2 immiscible substances allowing them to be mixed .
What are viscosity enhancers
Substance which causes solution to be more fluid.
What’s a hydrophilic emulsifier
A substance that produces oil in water solution
