Week 5 Solubiltiy Flashcards
Why is Solubility important in pharmacy?
Solubility determines the amount of bioavailability, the case of RITONAVIR has shown its importance for patients and pharmaceutical companies
Define Solubility!
Is the maximum quantity of a drug that can be dissolved at a given temperature –> Saturation: Solution may be saturated and have different concentrations
What is the Heat of the solution?
Heat released or absorbed when a drug is dissolved in a solvent
dH1 = separation of solutes
dH2 = separation of solvent
dH3 = Formation of solute-solvent-interaction
How can temperature affect solubility?
Endothermic reaction: solubility increases with increase of temperature
Exothermic reaction: solubility decreases with increase of temperature
Nonthermal: No effect with changes of temperature
How can Ionization affect solubility?
Polar groups: COOH, OH, CHO
Complexation: I2 + I (-) -> I3 (-) Lugols Iodine solution
pH: weak basic drug in acidic medium, weak acidic drug in basic medium
How can intermolecular interaction affect solubility?
intramolecular(solute-solute/solv-solv) has to be replaced with intermolecar interaction (solute-solvent)
Dipole-diopole
Ion-Dipole
Hydrogen-bonding
Solubility of Inorganics/Salts
Monovalent are more soluble than Di and Polyvalents
How can Salt affect solubility?
Salting in: weakens self-aggregation of proteins
Salting out: Steal H20 molecules away from proteins
What is the relation between melting, freezing point, and solubility?
Solubility decreases with increasing melting and freezing point
high melting point reflects strong intermolecular force making it less soluble
Solubility of organic molecules
Molecular weight decreases water solubility
1 polar functional group: soluble if less than 5 carbons
branched chains -> more soluble
What compounds are dissolved by polar solvents and what kind of interaction is important?
charged and uncharged compounds, hydrogen bonding is more important than polarity (see glucose)
What is the role of semipolar solvents? Name examples!
They act as intermediate solvents to improve miscibility between polar and nonpolar solvents
Propylene glycol and alcohol
When are nonpolar solvents used?
used to dissolve non-polar compounds through induced dipole/induced dipole interactions
used in pharmaceutical manufacturing or for extraction
Difference between amorphous and crystalline formulations in terms of solubility?
Crystallines are more stable –> less likely to involve in solute-solvent interaction -> less solube
Amorphous: structure is less organized –> more soluble
Solutions of gases in liquids
almost all gases soluble in liquids
Solubility is inversely proportional to temperature and direct proportional to pressure
