16.1 Practical techniques in organic chemistry

Round-bottom or pear-shaped flask Receiver Screw-tap adaptor Condenser Still head

Round-bottom or pear-shaped flask Condenser Rubber tubig Stand and clamp Heat source

A heating mantle so there is no naked flame present

A water bath

Flask clamped by neck Add reaction mixture and anti-bumping granules Apply thin layer of grease to ground-glass joint on condenser During reflux, condenser kept in upright position Rubber tubing to connect inlet of condenser to tap and outlet to sink

Contents boil smoothly If not used, large bubbles at bottom of liquid make glassware vibrate or jump violently

Once reflux is complete, crude liquid or solid product needs to be purified to remove any by-products and remaining reactants

Common method used to separate a pure liquid from its impurities

Round-bottom or pear-shaped flask Condenser Rubber tubing Heat source Stand and clamp Screw-cap adaptor Receiver adaptor Still head Thermometer

Add some water The layer that gets bigger is the aqueous layer

Separate using separating funnel • Ensure that tap of separating funnel is closed • Pour mixture of liquids into separating funnel, place stopper in top of the funnel and invert to mix contents • Allow layers to settle • Add some water to see which layer increases in volume - this is the aqueous layer • Place conical flask under separating funnel, remove stopper and open tap until whole of lower layer has left funnel • Place second conical flask under separating funnel to collect other later Can remove impurities by adding aqueous sodium carbonate and shaking Any acid present will react releasing CO2

Traces of water removed by adding drying agent (an anhydrous inorganic salt) • Add organic liquid to conical flask • Using spatula, add some of drying agent to liquid and gently swirl contents to mix together. • Place a stopper on flask to prevent product from evaporating away. Leave for about 10 mins • If solid has stuck together in lump, still some water present. Add more drying agent until some solid dispersed in solution as fine powder • Decant the liquid from the solid into another flask, if liquid is dry, it should be clear