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Pre-Lab 1
Mod Organic Chem I (CHEM 2211)
University of Georgia
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Experiment #1 Brandon Wilhoit TA: Mariia Sutton Recrystallization of an unknown organic compound Introduction: Purification one of the most vital parts to any lab experiment. Normally, the chemical procedures when we synthesize unique organic compounds result in impure mixtures of liquids and solids. Before these compounds are of any use, they must be isolated by one another and then be purified. In today’s lab we will be isolating and identifying an unknow organic solid. The method we will be using is recrystallization which is an important laboratory method used for the purification of a solid compounds. We will be purifying the unknown compound through recrystallization and identifying it by its melting point. Safety: Be careful with boiling water and hot glassware Never heat a closed vessel Always add a boiling chip to any liquid before heating it Safety glasses and gloves are to be worn at all times Procedure: 1. Obtain 1 gram of impure substance from your TA, before you measure out your sample be sure stir the mixture as this a heterogeneous blend of pure unknown and inert sea sand. 2. Acquire a 125 mL Erlenmeyer flask and add roughly around 25-50 mL of water and several boiling chips. 3. While using a hotplate, heat up the water to a moderate boil. Be careful while heating the flask to fast as this can cause it to evaporate a significant amount of the water before you use it. 4. Place another 125 mL Erlenmeyer flask on a second hotplate which has 1 gram of the solid unknown along with a boiling chip. 5. Using the ring clamp as a handle, begin to slowly pour about 5-10mL of boiling water into the flask that has the impure solid. This not have to be an exact measurement of water. Estimate the volume instead of using a graduated cylinder and measuring it out. 6. Once the water has been added make sure to swirl the mixture for approximately one minute while using the hotplate to maintain the solutions temperature. While doing this you may need to add about 3-5 mL of boiling water and continue swirling until the unknown solid is finally dissolved. When adding more boiling water make sure to swirl the mixture for about 1 minute in between every addition of water to help the dissolution process. 7. If you happen to see clumps developing in the mixture use the stirring rod or spatula to break it up. Be aware that there will still be insoluble impurities (Sea Sand) in the bottom of the flask after the unknown solid has completely dissolved. This is to be expected. It is important not to over use the solvent to dissolve your unknown as this can cause a decreased percent recovery at the end of your experiment. 8. Begin to set up a gravity filtration system which involves a glass short stem funnel covered with fluted or folded filter paper while covered with a watch glass and placed on top of a 125mL Erlenmeyer flask (See Figure 1). The flask should have a couple of milliliters of boiling water in it that way the apparatus will stay warm during the filtration process. Use a hotplate to maintain the waters temperature. Remember that the water you add in the flask will be added to the total amount of water your unknown solid must be recrystallized from later on. 9. It is important that the solution maintains being hot during filtration. If the temperature of the solution drops drastically, then some of your unknown may crystalize in the filter paper instead of it passing through and ending up in the flask. Make sure to moisten the Acetanilide 135 g/mol 114 ºC Benzamide 121 g/mol 125-129 ºC Benzoic Acid 122 g/mol 122 ºC Ethyl3, 5-dinitrobenzoate 240 g/mol 94-95 ºC m-Nitrobenzoic 167 g/mol 139-141 ºC o-Tulic acid 136 g/mol 259 ºC Salicylic acid 138 g/mol 158 ºC Vanillin 152 g/mol 81-83 ºC
Pre-Lab 1
Course: Mod Organic Chem I (CHEM 2211)
University: University of Georgia
