Comparing the Chemical Properties of Alkanes and Alkenes

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Andrew McNally/ 17th March 2003 /Science Access.

Comparing the Chemical Properties of Alkanes and Alkenes

Aim

To investigate and compare the chemical properties (notably the reactivity) of the alkane Cyclohexane and the alkene Cyclohexene.

Hypothesis

Based on previous knowledge of alkanes and alkenes I suggest the chemical properties of the two will be similar as both are fuels, however, as alkenes (but not alkanes) contain a carbon double bond (C=C) some of the chemical properties will differ.

Method

Apparatus:

  • Hard glass watch glass
  • Wood splints
  • 10 dry test tubes (two of which covered in aluminium foil)
  • 10 tight fitting bungs (to seal the test tubes)
  • Test tube rack
  • Bromine dissolved in an inert solvent (Bromine Water)
  • Acidified Potassium Manganate (VII) solution
  • Concentrated Sulphuric acid (H2SO4) 

                               

Procedure A: Combustion

  1. Place 3-4 drops of cyclohexane onto the watch glass
  2. Light a splint and use this to light the cyclohexane
  3. Record observations (e.g. Colour of the flame, amount of soot produced) 

Procedure B: Reaction with Bromine

      1.    Place 3-4 drops of cyclohexane into a test tube and the same again into one of the         aluminium wrapped tubes.

  1. Into each tube place equal amounts of the Bromine water (approx. 5 drops in each) and fit the bung.
  2. Keep the aluminium wrapped tube in a dark place (e.g. fume cupboard) and the other tube in as light a place a possible; holding by a window is sufficient.
  3. After approximately 3 minutes remove the foil and make observations as to the appearance of the two solutions. (One has been exposed to light the other not).
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Procedure C: Reaction with Acidified Potassium Manganate (VII)

  1. Place 3-4 drops of cyclohexane into a test tube
  2. Into the tube put 5-6 drops of the acidified Potassium Manganate (VII)
  3. Fit the bung and shake well
  4. Record observations of the reaction mixture

Procedure D: Reaction with Concentrated Sulphuric Acid (H2SO4)

  1. Place 1cm³ of cyclohexane into a test tube
  2. Into the tube put 1cm³ of concentrated sulphuric acid
  3. Fit the bung and agitate slightly
  4. Record observations of the reaction mixture (Do they react? Do they separate? Do they mix but not ...

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