Synthesis of a Haloalkane (OCR AS Chemistry A): Revision Note

PAG 5.1: Synthesis of a haloalkane

Synthesis of a haloalkane from an alcohol

1. Measure 8 cm³ of 2-methylpropan-2-ol using a measuring cylinder

2. Pour the 2-methylpropan-2-ol into a separating funnel

3. In a fume cupboard, add 20 cm³ of concentrated hydrochloric acid in small 2–3 cm³ portions

   • After each addition, release the pressure by briefly opening the stopper

4. Leave the funnel to stand for 20 minutes in the fume cupboard

   • Gently shake it every 2 minutes

5. Allow the layers to separate

6. Open the tap and discard the lower aqueous layer

7. Add sodium hydrogen carbonate solution in small portions

   • Gently shake and release the pressure regularly

   • This step removes acidic impurities

8. Once the layers separate again, discard the lower aqueous layer

9. Transfer the organic layer into a clean, dry conical flask

10. Add two spatulas of anhydrous magnesium sulfate to dry the organic layer

11. When the mixture turns clear, decant the liquid into a distillation apparatus

12. Distil the product

    • Collect the fraction that boils between 47 – 53 °C

Practical skills reminder

This practical develops key techniques, including:

• Measuring and transferring volumes accurately using a measuring cylinder and separating funnel

• Recording and controlling reaction time and temperature during separation and distillation

• Using a fume cupboard to safely handle volatile and corrosive reagents

• Drying an organic product with a solid drying agent

• Performing distillation to isolate a pure liquid within a specific boiling range