Practical Techniques

Practical Techniques in Medicine

Spectroscopic Techniques

  • Nuclear Magnetic Resonance (NMR): Used for structure elucidation of organic compounds.
    • 1H NMR: Determines the type and number of hydrogen environments.
    • 13C NMR: Provides information on carbon environments.
    • Chemical shifts: Vary according to the chemical environment of the atoms.
  • Mass Spectrometry: Provides information about the molecular weight and structure of a compound using ionisation techniques.
    • Electron Impact (EI): Primary ionisation technique with fragmentation patterns useful for structure elucidation.
    • Electrospray Ionisation (ESI): Useful for larger, more fragile molecules with less fragmentation.
    • Time-of-flight (TOF) analyser: Assesses ions by their time of flight, separating ions by mass/charge ratio.

Synthesis of Medications

  • Aspirin synthesis: Consists of an esterification reaction between salicylic acid and acetic anhydride.
  • Paracetamol synthesis: Involves the acylation of 4-aminophenol with acetic anhydride.

Pharmacokinetics and Drug Action

  • Absorption, Distribution, Metabolism and Excretion (ADME) processes influence the bioavailability and efficiency of a drug.
  • Drug receptors: Most drugs exert their effects by binding to protein receptors. The nature of the binding (competitive, non-competitive) impacts pharmacodynamics.
  • Drug metabolism: Typically happens in liver, where drugs are often converted to more polar metabolites to aid excretion.

Molecular Modelling

  • Molecular models can be used to predict the shape, bond angles and relative size of molecules.
  • Information on intermolecular forces can be predicted and analysed from molecular models for a variety of compounds.
  • It’s pivotal to use the electron pair repulsion theory to understand the shape of molecules.

Thermal Techniques

  • Melting Point Determination: Useful for assessing the purity of a synthesised compound.
  • Heating under Reflux: Allows reaction to occur at higher temperatures without losing components to evaporation.

Chromatographic Techniques

  • Thin-Layer Chromatography (TLC): Allows for identification of compounds based on their ability to travel up a stationary phase.
  • Column Chromatography: Separates compounds on the basis of their interaction with a stationary phase.
  • High-Performance Liquid Chromatography (HPLC): Can separate and identify components of a mixture based on their actual amounts and properties.
  • Gas Chromatography (GC): Useful for volatile compounds, separation based on interaction with a stationary phase.