ORGANIC ANALYSIS

• Test for alcohols

  1. Using acidified potassium dichromate

  2. Change from orange to green
• Test for aldehydes and ketones using Fehling's

  1. Aldehydes - blue solution to brick red precipitate

  2. Ketones - no visible change
• Test for aldehydes and ketones using Tollens' reagent

  1. Aldehydes - silver mirror

  2. Ketones - no visible change
• Test for alkenes

  1. Using bromine water

  2. Brown -> colourless
• Test for carboxylic acids

  1. Using carbonate, reacts by the following equation: CO32- + 2H+ -> CO2 + H2O

  2. Bubble gas produced through limewater and it will turn cloudy
• Mass spectrometry

  Used to find the relative molecular mass (Mr) of a compound
• Peaks in mass spec

  • Show fragments of the original molecule
  • Last peak is the M+1 peak or the molecular ion peak, which is the same as the relative molecular mass of the molecule
• High resolution mass spectrometry

  Used for identifying different molecules with the same molecular mass rounded to the nearest whole number
• Infrared spectrometry

  Uses infrared radiation to increase the vibrational energy of covalent bonds in a sample
• Frequency of infrared radiation absorbed by a covalent bond

  • Depends on the atoms that are either side of the bond
  • Depends on the position of the bond in the molecule (e.g. OH in alcohols and OH in carboxylic acids)
• Fingerprint region

  Lies between 500 - 1500cm-1
• Infrared radiation

  Greenhouse gases absorb infrared radiation and re-emit this back towards the earth
• HOW TO MAKE TOLLENS

  • dissolve silver nitrate in aqueous ammonia
  • heat
• HOW TO MAKE FEHLINGS

  • Copper II ions dissolved in sodium hydroxide