Paper 3: Required practical 10 - Preparation of organic solids and liquids

• Synthesis of the compound (using reflux, distillation) • Filtration (usually vacuum filtration) • Purification (recrystallisation)

• Substance is boiled in a pear-shaped or round-bottomed flask • As it evaporates, it is cooled by the water in the liebig condenser and so condenses back into a liquid and drips back down into the flask to be heated again

• Allows heating for a long period of time • Prevents the flask from dry boiling • Prevents volatile reactants/products escaping • Ensures even heating

Using a buchner funnel and buchner flask, connected by rubber tubing to the vacuum source * The funnel contains a layer of filter paper * Pour the substance onto the filter paper and the liquid will be sucked through via vacuum filtration into the flask * The solid will remain on the paper

• Add a minimal amount of hot solvent • Filter to remove insoluble impurities • Place in an ice bath • Filter under reduced pressure • Wash and dry to remove soluble impurities

• Place a small sample of the solid in a capillary tube • Melt using the melting apparatus available, measuring the temp with a thermometer • A pure substance will usually melt at a single temperature but an impure substance wil melt over a range of temperatures (lower than the pure substance) • Record the starting and ending points of the melting, ehen the first crystal can be seen to melt and when the last crystal becomes liquid respectively • You can compare the melting point to known values to identify the substance

• Use a separating dunnel to isolate the organic layer from the aqueous layer • Add anhydrous MgSO4 to the organic product to get rid of all water • You can then purify the liquid by distillation, which separates the substances by boiling point