Purification of Triptycene

1. Purification of Triptycene

2. Agenda Purification of Triptycene by a Chemical Reaction. Characterization of the pure product by: 1. Thin Layer Chromatography. 2. Melting Point. 3. 13C NMR spectrum.

3. How Did We Make Triptycene ?

4. Purification Impurities from solid can be removed by: 1. Extraction. 2. Recrystallization 3. Column Chromatography. But we are going to do a Chemical Reaction to remove the impurity !!!

5. Possible Impurities Anthranilic Acid is cannot be impurity due to the following reasons. 1. It cannot be the impurity because, we converted all of them into very active BENZYNE by reacting them with Isoamyl Nitrite. 2. The UNREACTED Anthranilic acid must have gone with aqueous basic solution.

6. Possible Impurities Isoamyl Nitrite and 1, 2 � Dimethoxyethane are also another possible impurities. But they are liquids. So they must have gone with our filtrate.

7. Possible Impurities The only reagent left is Anthracene, so our impurity must be it. We know that anthracene is a diene because it has conjugated double bonds.

8. Reagent to Remove Impurity We are going to use maleic anhydride to remove the diene impurity. It�s a Dieneophile.

9. Theory Each compound has different reactivity with different chemicals. Crude product contain Triptycene and Anthracene. Anthracene forms an ADDUCT with Maleic Anhydride. Triptycene DOES NOT REACT with Maleic Anhydride under such conditions.

10. Chemical Reaction

11. How can we remove the Adduct???

12. Procedure Take all the crude product and add 20 mL of triethylene glycol dimethyl ether. Add 1 gram of Maleic Anhydride to the above mixture. Set up a refluxion apparatus. Heat the mixture till its boiling (Boiling Point of the solvent is 222 ?C). Reflux the mixture for five minutes.

13. Procedure Cool the mixture for 5 minutes and add: 1. 10 mL of 95 % Ethanol 2. 35 mL of 10 % NaOH Cool the reaction mixture thoroughly with ice bath (may be for 10 � 15 minutes). Filter the solid using Buchner funnel and wash the solid with chilled Methanol � water mixture ( 4:1)

14. Procedure Dry the solid using suction pump and then in air for 10 minutes. Dissolve all the solid in dichloromethane (10 mL per gram of the solid). Filter them using funnel and cotton plug. Rinse the funnel and cotton plug with plenty of methylene chloride and pool all of them.

15. Procedure Take 50 mL RB flask, transfer all the methylene chloride solution and gently boil the solution. Slowly add methanol into the warm solution (two volumes of methanol for each volume of methylene chloride) until crystallization begins. After seeing the crystal, do not add more methanol

16. Procedure Slowly cool the solution to room temperature and then keep it ice bath for half an hour to complete the crystallization. Filter the crystals using frit funnel and dry them as much as you can using pump. Weigh 0.5 gram out of it and transfer into a vial.

17. TLC Characterization We are going to use the TLC technique to check the purity of the compound. Take small amount of anthracene, pure triptycene and the compound you made it in a separate test tube. Dissolve them using minimum amount of methylene chloride.

18. TLC Characterization Take a chromatogram of size 8 cm x 3 cm Keep tiny spot of all three compound on the line of origin. Use different capillary for different compounds Use hexane as the mobile phase and run the TLC. Note: Hexane move fast, watch carefully.

19. TLC Characterization Use UV � lamp to visualize your chromatogram. Why can�t we use Ninhydrin??? We do not have free �NH2 group in the compounds.

20. TLC Characterization

21. Characterization Find the melting point. Give the dry sample for 13C NMR spectrum.

22. Note Work in the same group where you were in. Make your own capillaries! Do not forget to save some triptycene.