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extract - CHEM 267 Extraction of Acids and Bases(revised...

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CHEM 267 . Extraction of Acids and Bases . (revised 7/10). This experiment is not spelled out in as much detail as were previous experiments. It requires careful preparation and careful lab technique. The notes below are basically changes and suggestions, NOT a detailed procedure. Details will be found in the lab text. Your detailed prelab will be prepared by you based on this handout and on the lab text. This experiment combines techniques learned in previous experiments (recrystallization , MP ) with a new technique, extraction . The separation is based on the acid/base properties of the substances in the mixture. To understand the principles behind the separation, it is essential that you understand the acid/base chemistry involved and why each species is soluble or insoluble in each layer (see p. 143). To help you with this, write out a flow diagram such as that on p. 142 and include it as part of your prelab outline. Also, as part of your prelab outline, calculate the amount of conc HCl needed to neutralize 1.15 mL of saturated sodium bicarbonate and the amount of conc HCl to neutralize 1.0 mL of 3 M NaOH (conc HCl = 12 M, sat’d NaHCO3 = 1 M). You will separate a mixture of three unknown components (one from each class) by extraction, purify the separate components by recrystallization, and identify the unknowns by MP. The possible compounds are: carboxylic acids: 3-toluic acid (MP 112°), benzoic acid (MP 122°), 2-chlorobenzoic acid (MP 142°), salicylic acid (MP 159°) phenols: 4-bromophenol (MP 66°), 4- tert -butylphenol (MP 101°), 2-naphthol (mp 123°) neutral compounds: vanillin (MP 81°), benzil (MP 96°), trans -stilbene (MP 125°), benzoin (MP 133°) You are given ample time (2 lab periods) in which to finish this exp. Each of you will work at a different pace. Think carefully about each step and don't rush. Label the tubes carefully so as not to mix them up. Do not think of the tubes as tube 1 and tube 2 as in the book. Instead, think of what chemical species is in each tube, why it is soluble in that solvent, and what each operation accomplishes. This will help you to better understand what you are doing and why, and help to decrease the possibility of error.
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