4.2.4 analytical analysis

• What happens when a molecule absorbs infrared radiation?

  It makes the covalent bond vibrate more
• What are the types of motion that occur when a bond vibrates?

  Stretching or bending motion
• What factors affect the amount of vibration of a bond?

  • Bond strength
  • Bond length
  • Mass of each atom in the bond
• How does infrared spectroscopy work?

  Every bond has a unique vibration frequency
• What happens to bonds during infrared spectroscopy?

  Bonds absorb radiation matching their vibration frequency
• What does missing frequencies in emerged infrared radiation indicate?

  It helps identify the compound’s functional group
• What do the peaks on an infrared spectrum represent?

  Absorbance of energy from infrared radiation
• What happens inside a mass spectrometer?

  • Organic compound is vaporised
  • Molecules lose an electron forming molecular ions
  • Excess energy makes bonds vibrate more
  • Vibration causes bond weakening
  • Molecular ion splits by fragmentation
• What is the symbol of a molecular ion?

  M+
• Is fragmentation predictable in mass spectrometry?

  No, it can happen anywhere in the molecule
• How is a molecular ion represented in mass spectrometry?

  It is the peak with the highest mass/charge ratio
• What is the molecular mass of the molecular ions equal to?

  Relative molecular mass of the compound
• What are the advantages of using mass spectrometry?

  • Cheap
  • Small quantities of samples required
• What is the main disadvantage of using mass spectrometry?

  The sample is completely destroyed