3.3.6 organic analysis

• Chlorine isotopes: 35Cl and 37Cl

  ratio of 35:37- 3:1
• Bromine isotopes: 79Br and 81Br

  ratio of 79:81- 1:1
• how does infra-red spectrometry work

  pass infrared through a molecule and it detects which wavelengths of light are absorbed and which pass through, different bonds absorb different frequencies of light so infrared can be used to identify functional groups
• what is the fingerprint region and how is it used

  the fingerprint region is below 1500cm-1 in the spectra, the fingerprint region of an unknown molecule will be an exact match with a known compound
• test for alkenes

  reagent: bromine water

  observation if present: orange solution to colourless solution

  other fg: no visible change
• test for halogenoalkanes


  reagent: silver nitrate (acidified)

  observation if present:

  chloro —> white precipitate

  bromo —> cream precipitate

  iodo —> yellow precipitate

  other fg: no visible change
• test for primary/secondary alcohols

  reagents: tollens reagent and fehlings solution
• test for carboxylic acids

  reagent: sodium carbonate/ NaHCO3

  observation if present: effervescence

  other fg: no visible change