Medicinal chemistry

Melting point determination

The melting point range of pure compounds will be very narrow (1-2 degrees)
Impure samples will melt at a lower temperature and have a larger range due to the disruption of the intermolecular forces

Simple distillation

a form of purification by separating liquids based on their boiling points
- heating a mixture of liquids
- Collecting the vapour produced
- vapour passed through a condenser
- Condensed back into liquid (distillate) 

Fractional distillation

form of purification
- involves a fracking column thar decreases in temperature as it moves away from the heat source
- the gradual decrease in temperature allows for separation by condensing the substance that will fall back into the flask
- the component with the lowest boiling point will be distilled first

Solvent extraction

separation based on polarity
1. a solvent is added to the original solution that is immiscible with the first
2. The solution is shaken to distribute the particles
3. The solvent particles then exist in the solvent which their polarities align with the most
4. the solvents are separated by decanting

Stereoisomerism

Molecules have the same structural formula but the way the atoms are arranged in a 3d space is different

Optical isomers

molecules that are non superimposable mirror images of each other
Molecules that can superimpose are achiral

Medical importance of chiral centres

• the arrangement of the atoms in a 3d space must interact in the correct orientation with the correct charge attraction for maximal interactions

• If molecules do not fit precisely into the active site of an enzyme the biological process does not occur optimally

Enzymes

• proteins made up of many amino acids bonded together that act as biological catalysts
  

Zwitterions

An ion with both a positive and negative charge simultaneously

primary structure

• the individual sequence of amino acids in the polypeptide backbone as joined by the amide bonds

Secondary structure

• involve hydrogen bonding between the peptide links

• Gives rise to two different orientations: alpha helix & beta pleated sheets

Tertiary structure

• determines the overall 3d shape of the molecule

• is a set of intermolecular forces within the same polypeptide unit

• refers to the types of bonds the peptide can make if the R groups are
  - non polar (dispersion)
  - Polar (dipole dipole)
  - Contains sulphur (disulphide bridges/covalent)
  - protonated/deprotonated (ionic bonds)
  - N-H, C-O or C=O (hydrogen bond)

Quaternary structure

• set of intermolecular interactions between different polypeptide units

• Held together by the same forces as tertiary

Denaturing of enzymes

• high temp and pH change - disrupts the secondary, tertiary and quaternary structures

• Low temp does not denature only slows down reaction