Solutions Flashcards
Dissolution
-Absorption
-Formulation
-Medicine incompatibilities
Absorption
Drugs usually need to be aqueous solution to be absorbed
Solute-solvent interactions
Attractive forces between solute and solvent are governed by the molecular structure of the solid and the nature of the solvent
Effects of solute structure
- small change in molecular structure
-addition/ removal of a functional group
Which is more polar; phenol or benzene and why?
Phenol is more polar and is more soluble because of the presence of OH- group
Hydrogen bonds can form with water.
acid + base»>
salt + water
effects of solute structure
- molecular shape
- Position of groups on benzene ring
Charged functional groups are more hydrophilic or hydrophobic
Hydrophilic
Polar solvents
-water
-methanol
-acetic acid
Relative permittivity Er - elements
water - 80
chloroform - 5
benzene - 2
(non-polar = much lower relative permittivity)
what is relative permittivity?
-Polar solvents dissolve ionic solutes by recuding the force of attraction between oppositely charged ions in crystalline solids; Na2CO3
-Polar solvents can even break covalent bonds
HCl + H2O> H3O+ + Cl-
Semi-polar solvents examples
Acetone (Er - 20.7)
Ethanol (Er 24.5)
Dimethyl sulfoxide (Er - 45)
explain what are semi-polar solvents
- dissolve polar + non-polar substances
- solvent molecule dipole moment on H-bonding groups enable polar solutes to be dissolved
- semi-polar solvents can induce a degree of polarity in non-polar solvent molecules e.g benzene (is soluble in ethanol)
Examples of non-polar solvents
- Alkanes
-Benzene - Oils and fats
explain non-polar solvents
- Low dielectric constant and lack of H-bonding groups prevent these solvents from dissolving ionic or polar solutes
- unable to break covalent bonds
- dissolve non-polar compounds only
- non-polar solutes are held on solution through van der waals interaction with the solvent
