Organic Analysis

• Tests for Functional Groups:

  • Alcohols:
  • 1° and 2° alcohols are identified using acidified potassium dichromate, turning from orange to green if present
  • 3° alcohols are not oxidised, and the potassium dichromate remains orange
  • Aldehydes:
  • Tollen’s reagent forms a silver mirror when added to the solution with an aldehyde present
  • Fehling's solution forms a brick red precipitate when heated if an aldehyde is present
  • Alkenes:
  • Bromine water changes from orange-brown to colorless in the presence of a carbon-carbon double bond
• • Carboxylic Acid - React with sodium carbonate to produce CO2, turning limewater cloudy if CO2 is present
• Mass Spectrometry:

  • Used to identify compounds and determine their molecular formula
  • High Resolution Mass Spectrometry allows determination of Mr to several decimal places, precise atomic masses are given to calculate the molecular formula
• Infrared Spectroscopy:

  • Uses infrared radiation to determine functional groups in organic compounds
  • Different bonds absorb radiation in varying amounts, allowing identification of functional groups
  • Characteristic peaks for different functional groups:
  • -OH Alcohol Group: 3230 - 3550 cm^-1
  • -OH Acid Group: 2500 - 3000 cm^-1
  • C=C Unsaturated Group: 1620 - 1680 cm^-1
  • C=O Carbonyl Group: 1680 - 1750 cm^-1
  • Fingerprint Region:
  • Contains tiny differences acting as a molecule's 'fingerprint' for identification
• Infrared absorption in the atmosphere, like with ozone, traps heat causing global warming

  • Human activity releasing chemicals like CFCs enhances the heating effect, leading to global warming