Preparation of Pure Diphenyl

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Experiment 2 Date: 24 January 2006

Title : Crystallization of a Crude Sample
Objective : Preparation of pure diphenyl via crystallization of crude diphenyl dissolved in ethanol.

Structural Formula of Organic Substances Involved :

Diphenyl Ethanol

Apparatus : Round-bottom flask (100 mL), measuring cylinder (50 mL), conical flask (50 mL), filter flask, beaker (100 mL), stemless glass funnel, Hirsch funnel, capillary tube, long glass tube, watch glass, glass vial, water condenser, retort stand, retort clamps, spatula, cork stand, fluted filter paper, filter paper for Hirsch funnel, electronic weigh, electrothermal heater, oven, aspirator, electrothermal device to determine melting point.

Chemicals : Crude diphenyl (3.0 g),
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Fluted filter paper is used also to increase the rapidity of filtration since almost the entire surface area of the filter paper is being used. By folding it in such a way, it also clogs up any possible tiny pores in the filter paper so that the results of filtration are maximized.

After filtration, the filtrate is allowed to cool slowly at room temperature in order to obtain the maximum amount of desired product with minimum impurities. It is not encouraged to cool the filtrate immediately in an ice bath as rapid cooling can cause the formation of very small crystals. Small crystals will make filtration more difficult as adsorption of impurities might occur, thus affecting the desired results.

When crystallization of the mixture is complete, it is again filtered, this time via vacuum filtration, using an aspirator and Hirsch funnel in a filter flask. Vacuum filtration serves to remove large amounts of mother liquor from the crystals. The residue of filtration is the crystals, which some of them may stick to the filter paper and the internal wall of the funnel. Cold alcohol is used to rinse the funnel’s walls to obtain the maximum product.

In the process of determining the melting point, a small portion of the crystals is grinded into powdery form using a capillary tube. Some of the powdery crystals are collected inside the