Experiment 1 - Extraction,Recrystallization,TLC Lab Report

Experiment 1 - Extraction,Recrystallization,TLC Lab Report...

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Experiment 1 A. Extraction and Recrystallization B. Thin Layer Chromatography (TLC) Lut Ming Cheng, 4957880, CHM2123, Section C TA: Wendy Campbell Due Date: September 22, 2008 1 – Theory and Mechanism In order to separate a mixture of organic components, extraction and recrystallization techniques are used to achieve the goal. Extraction technique would separate the mixture into two immiscible phases by acid-base reaction. Recrystallization technique would then purify the achieved product by filtrating out the soluble impurities. Furthermore, TLC is a technique that is commonly used to confirm and check the purity of the achieved product. The rate and the distance of products travelled on the TLC plate are based on the polarity of your product and solvents. Compounds that are higher in polarity would adsorb and have more interaction with the stationary phase (ie. silica gel). Therefore, smaller value of R f would be observed for polar compounds. In this experiment, mixture of benzoic acid and benzil is extracted by applying sodium hydroxide to deprotonate the benzoic acid. The deprotonation of benzoic acid gives a product of sodium benzoate. Sodium benzoate is soluble in water, therefore it would stay in the aqueous phase. Benzil is insoluble in water, and do not have reaction with the sodium hydroxide. Therefore, benzil would remain in the organic phase for the extraction. Balanced equation: C 6 H 5 COOH + NaOH C 6 H 5 COO - + Na + O OH + Na + O - H O O - + Na + From the extraction, benzil and sodium benzoate are both separated, and are in organic and aqueous phases respectively. Sodium benzoate is then protonated by concentrated hydrochloric acid. After the protonation, benzoic acid is formed. Balanced equation: C 6 H 5 COO - + HCl C 6 H 5 COOH + Cl - O OH + O O - + H Cl Cl - Recrystallization of benzil and benzoic acid is proceeded. Melting point and TLC techniques are used to verify and confirm the purity of the products.
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2 - Table of reagents and solvents Part A: Extraction and Recrystallization Compound Mol. Wt (g/mol) Amount Density 2 (g/mL) mmol equiv. Benzoic acid 122.12 - 1.32 - - Benzil 210.23 - 1.084 - - HCl 36.46 - 1.18 - - Sodium sulphate 142.04 1 g 2.68 7.04 1.0 CH 2 Cl 2 84.93 20 mL 1.3255 312.14 44.3 H 2 O 18.015 3 mL 0.998 166.48 23.7 Ethanol-water (5:1) - 3 mL - - - 2M NaOH 39.997 5 mL 2.1 10 1.4 3- Experimental procedures Ref: pages 6-10 of the Organic Chemistry II lab manual 4- Observations Part A: Extraction and Recrystallization Important Steps Observations Mixture #133 of benzoic acid and benzil is obtained The physical properties of the mixture: bright yellow in color; crystals form; opaque Dissolution of mixture in dichloromethane The solution became yellow and opaque. Extraction of the mixture
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Experiment 1 - Extraction,Recrystallization,TLC Lab Report...

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