3.6- Organic analysis

• What does bromine water test for?

  Double bonds - it turns colourless
• If bromine water decolourises what does this mean

  Presence of an alkene group

  
• What does silver nitrate test for?

  Chloroalkane
• What is a positive result of the silver nitrate test

  White precipitate

  (chloroalkane)

  
• What do you use acidified dichromate to test for


  primary or secondary alcohols

  Ketones / aldehydes

  
• What is a positive result for acidified dichromate

  Aldehyde present

  Orange -> green

  
• What does Tollen's reagent do?

  oxidizes aldehydes but not ketones
• What is a positive result for Tollen's reagent ?

  silver mirror or black precipitate

  
• What colour with Fehling's solution indicates an aldehyde

  Brick red

  
• What does effervescence with a hydrogen carbonate or carbonate indicate

  Carboxylic acid
• Test for carboxylic acids

  add an equal amount of sodium carbonate (NaHCO3) , fizzes and bubbles produced. CO2 produced bubbled through limewater turns it cloudy.
• Test for halogenoalkanes


  1. Add NaOH and warm

  2. Acidify with HNO3

  3. Add AgNO3

  
  

  Precipitate of AgX
• How does infrared spectroscopy work?

  Bonds in a molecule absorb infrared radiation at characteristic wavenumbers
• What does fingerprinting allow

  identification of a molecule by comparison of spectra
• How does infrared radiation lead to global warming

  - bonds within molecules of these greenhouse gases absorb infrared radiation.

  -increases kinetic energy causing the gases to heat up.

  - temperature of the atmosphere increases,

  - warms the earth
• What does an O-H alcohol group look like on infrared spectroscopy


  Strong broad band ( u-shaped )

  
• What does an O-H acid group look like on infrared spectroscopy


  OH bond band with C-H bumps

  
• What does an C=O group look like on infrared spectroscopy

  Downwards peak at 1680-1750 cm^3

  
• What does an C=C alcohol group look like on infrared spectroscopy


  Strong peak at 1620-1680