Recrystallization Spring Fall 09

Purifying Acetanilide by Recrystallization

Definition ,[object Object],[object Object],[object Object],[object Object],[object Object]

[object Object],[object Object],[object Object],[object Object]

Choosing a Recrystallization Solvent ,[object Object],[object Object],[object Object],[object Object],[object Object],Note: 1- Be careful that your compound does not melt before the solvent boils. 2- Make sure that you record your observations in a chart like the one shown here. Soluble Soluble Soluble Solvent’s Boiling Point Insoluble Insoluble Soluble Room Temperature C B A

Step 1 – Choosing the Right Solvent Petroleum Ether Water Ethanol Acetone Dissolves at Room Temperature? YES NO STOP Bad Solvent Dissolves? YES NO STOP Bad Solvent CRYSTALS? YES Good Solvent NO Bad Solvent Heat Ice-water bath Sample added to solvent

Step 2 – Dissolving the Compound ,[object Object],[object Object],[object Object],1 - Heat some solvent to boiling. Place the solid to be recrystallized in an Erlenmeyer flask. 2 - Add small amount (1 mL) of the hot solvent into the flask. (Use a Pasteur pipet) 3 - Swirl the flask 4 - Place the flask on the hot plate to keep the solution warm 5 - Repeat steps 2 to 4 until you have dissolved the compound, and then add the 5% excess.

Step 3 - Decolorizing ,[object Object],[object Object],[object Object],[object Object],[object Object]

Decolorizing the Solution ,[object Object],[object Object],[object Object],[object Object]

Folding a Fluted Filter Paper 1- Fold the paper in half. Crease sharply. 2- Fold in half again. 3- Fold each quarter in half again, with all creases facing up. 4- Fold each eighth in half again but this time make the folds in the opposite direction to the one you have been doing.

Step 4 – Forming Crystals ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

[object Object],[object Object],[object Object],Step 5 – Isolating Crystals

Isolating Crystals Disconnect the vacuum. Carefully remove the filter paper and solid from the funnel. Set the filter cake on a watch glass to dry. Wet filter paper with solvent. Turn on vacuum. The solution containing the crystals is poured onto the filter. After the mother liquor has been pulled through the filter, wash crystals with small portions of ice cold solvent .

Isolating Crystals ,[object Object],[object Object],[object Object],[object Object],[object Object]

Step 6 – Recovery Analysis (Next Week) ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

Procedure Cautions ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

Recrystallization Spring Fall 09

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Recrystallization Spring Fall 09