Lab 1 Chm 412 – Recrystallization and Melting Point
CHM 412ORGANIC CHEMISTRY EXPERIMENT 2: RECRYSTALLIZATION AND MELTING POINTChemicals- Acetanilide about 1-2 gApparatus 1. 1 Erlenmeyer flask2. 1 hot plate3. 1 short stem/stemless gravity filter funnel4. 1 beaker (100ml)5. 1filter paper6. 1 Buchner funnel7. 1 Buchner flask8. 1 rubber hosesA vacuum pumpA retort stand1 watch glass3 melting-point capillary tubes1 long pieces of glass/plastic tubeA melting point temperature determining apparatusProcedure Impure acetanilide about 1-2 g was placed in a Erlenmeyer flask.Heating of the water using hot plate until boiling was done and minimum amount of hot water was added to dissolve the acetanilide and soluble impurities while continuously h eating the mixture at the boiling point.
The hot water was added little by little until all the acetanilide dissolves.As a precaution, do not continue to add the solvent in attempts to dissolve the insoluble contaminants.It was noted that the acetanilide was dissolve in hot water forming an oily layer. Hence, boiling water was added enough to dissolve the oils.The hot solution was filtered into a 100 ml sized beaker using a short stem or stemless gravity filter funnel and fluted filter paper. The clear filtrate was cooled gradually at room temperature and allowed the compound to crystallize. To crystallize even more compound the beaker was cooled in ice bath.After 30 minutes the the crystal was collected in buchner funnel and the crystal was rinsed with not more than 20 ml ice cold water.The crystal was transferred onto a watch glass and was dried in the oven. To prepare a solid sample for a melting point determination, one of the end melting-point capillary was sealed using hot temperature and then the open end of the melting-point capillary was pressed down on the sample so that the sample is forced up into the tube.Then the tube was dropped into a long piece of glass tubing in upright position to knock down the sample to the closed end.The capillary was introduced into a melting point temperature determining apparatus and start heating. Lastly the sample was watched through the magnifier when its start to melts and was noted the temperature range.DiagramsGRAVITATIONAL FILTRATION[pic 1]BUCHNER FILTRATION[pic 2]Data and Results:Weight of acetanilide solidWeight (g)Before recrystallize acetanilide solid1.8189After recrystallize acetanilide solid0.3488Percentage yield (%)Weight after recrystallize acetanilide solid(g) × 100Weight before recrystallize acetanilide solid(g)0.3488 × 1001.8189=19%Melting ResultsStart (0C)End (0C)Rough(a) 88.0(b) 119.0Accurate 1(c) 85.0(d) 124.0Accurate 2(e) 90.0(f) 124.0Average of melting point range=(c + e)/2 – (d + f)/2= 85.0 + 90.0 + 124.0 + 124.0 2 2= 87.5 0C – 124 0C