Chlorination of 2-methylpropan-2-ol with conc HCL

• Procedure

  1. Pour 10 cm3 of 2-methylpropan-2-ol and 35 cm3 of concentrated hydrochloric acid into a large conical flask

  2. Place the bung in the mouth of the flask. Gently swirl again, then remove the bung to release the pressure

  3. Continue swirling the mixture with the bung fitted, and then releasing the pressure, for around 20 minutes

  4. Add approximately 6 g of powdered anhydrous calcium chloride to the flask and swirl until it has dissolved

  5. Transfer the reaction mixture to a separating funnel. Allow the mixture to settle into the two layers. Run off and discard the lower layer

  6. Add approximately 20 cm3 of sodium hydrogencarbonate solution to the separating funnel. Swirl the funnel. Run off and discard the lower aqueous layer

  7. Repeat the washing with sodium hydrogencarbonate solution, shake the separating funnel, and release the carbon dioxide gas produced, at frequent intervals

  8. Run off the organic layer into a small conical flask. Add a full spatula of anhydrous sodium sulfate. Leave the mixture until the liquid looks completely clear, swirling occasionally

  9. Decant the organic liquid into a 50 cm3 pear-shaped (or round-bottomed) flask

  10. Set up the flask for distillation

  11. Collect the fraction boiling between 50 °C and 52 °C

  12. Place your pure product in a labelled sample tube
• What are the safety precautions needed ?

  fume cupboard

  eye protection

  avoid skin contact

  Avoid inhaling vapours.

  The product of the distillation process is flammable.

  The fumes from the concentrated hydrochloric acid are toxic and corrosive and must not be inhaled, especially by anyone with a respiratory problem.
• Diagram

  A) thermometer

  B) water out

  C) loose clamp

  D) clamp or clip

  E) water in

  F) clamp

  G) impure product

  H) water

  I) heat

  
• What are the tests needed to be done on the distillate?

  1. Place a few drops of the distillate in a test tube.

  2. Add 5 cm3 of ethanol and 1 cm3 of aqueous sodium hydroxide to the test tube.

  3. Warm the mixture in a water bath.

  4. Add excess nitric acid to the mixture followed by a few drops of silver nitrate solution.
• What is an important learning tip?

  you can check the purity of a substance by measuring its boiling temperature
• Write an equation for the reaction of 2-methylpropan-2-ol with concentrated hydrochloric acid.

  (CH3)3COH + HCl → (CH3)3CCl + H2O
• What is removed from the crude product when it is shaken with sodium hydrogencarbonate solution?

  (unreacted) HCl
• 1. methylpropan-2-ol


  Boiling temperature: 82 °C, Soluble in water
• 1. chloro-2-methylpropane


  Boiling temperature: 51 °C, Insoluble in water
• 1. methylpropan-2-ol


  • Can form hydrogen bonds
• 1. chloro-2-methylpropane


  • Cannot form hydrogen bonds
• 1. methylpropan-2-ol


  Able to form hydrogen bonds with water, so it is soluble in water
• 1. chloro-2-methylpropane


  Cannot form hydrogen bonds with water, so it is insoluble in water
• Intermolecular hydrogen bonds in 2-methylpropan-2-ol


  Stronger than the dipole-dipole attractions and London forces between molecules in 2-chloro-2-methylpropane
• Stronger intermolecular bonds in 2-methylpropan-2-ol

  More energy is required to separate the molecules