TECH 0705 Post-Lab Questions: Seperating Acids and Neutral Compunds by Solvent Extraction

1. Calculate percent recovery... not hard
2. When the first washing was done with NaOH, the strong attraction of the OH- pulled both compounds into the aqueous solution, leaving nothing to react with the acidification of the NaHCO3 layer.
OR
Appartently, you had benzoic acid, naphthalene, and 2-naphthol dissolved in ether. If you mistakenly extracted that solution with aqueous NaOH, then:

C6H5COOH + NaOH ===> C6H5COO-Na+ + H2O

C10H7OH + NaOH ===> C10H7O-Na+ + H2O

C10H8 + NaOH ===> No reraction

So both the benzoate and the 2-naphtholate would have gone into the water solution and the naphthalene remained in the ether solution. If you had extracted the ether solution with NaHCO3 solution next, only the naphthalene would be left in the ether solution, nothing would go into the NaHCO3 solution, and no crystals would be formed on acidification of the NaHCO3 solution.


3. p-tert-butylphenoxide anion (The sodium salt of p-tert-butylphenol)

4.Dichloromethane would sepaprate into the lower layer of the separatory funnel instead of the top, making extraction more difficult.  Instead of using the funnel's stopcock, one would need to extract the top layer from above, leaving the bottom layer intact for further washes. (Check density)
 The only change you would make is you would save the opposite layer. For example, if you were extracting an organic into the organic layer (tbme), you would save the top layer and discard the bottom (aqueous). If you used dichloromethane instead, you would save the bottom layer (MeCl2) and discard the top (aqueous).


5. Make a flowchart (http://i.imgur.com/gji6F.gif) also refer to (http://www.sas.upenn.edu/~zhall/flowchart.html) for details and cool stuff and unicorns and cute puppies




6. Lower/wider melting point range than expected implies less purtiy, nuff said

TECH 0705 Results: Seperating Acids and Neutral Compunds by Solvent Extraction

Results
SET 1:  
Weight Before Extraction
p-Toluic Acid-0.513g
Acetanilde-0.256g
p-Tertbutylphenol-0.517g

Weight After Extraction
p-Toluic Acid-0.760g
p-Tertbutyl phenol-0.149g


                                 Expected Melting Point            Experimental Melting Point      
p-Toluic Acid                           180-182                                      174-180

p-Tertbutylphenol                    98-101                                        91-98

SET 2:  

Weight of initial acetanilide: 0.25606 g
Weight of initial p-toluic acid: 0.6079 g
Weight of initial p-tert-butylphenol: 0.5547 g 
Mass of filter paper to filter out p-toluic acid: 0.013 g
Mass of test tube used to collect p-toluic acid: 7.934 g
Mass of filter paper to filter out p-tert-butylphenol: 0.006 g
Mass of test tube used to collect p-tert-butylphenol: 7.986 g
Mass of large test tube used to collect acetanilide: 38.7405 g
Weight of p-toluic recovery and test tube: 8.507 g
Weight of p-tert-butylphenol recovery and test tube: 8.172 g
Weight of acetanilide recovery and test tube: 39.141 g
Melting range of p-tert-buyltphenol: 82-89 C.
Melting range of p-toluic acid: 179-185 C. 

 

 SET 3:
Mass of the acetanilide: 0.31 g.
Mass of  the p-toluic acid: 0.57 g.
Mass of the p=tert-butylphenol:  0.45 g.

Isolating P-toluic Acid:
Mass of the filter paper: 0.0061 g.
Mass of dry p-toluic acid, test tube and filter paper: 5.476 g.
Mass of recovered p toluic acid:  0.084 g.
Measured melting point of p- toluic acid:  179.3-180.2 degrees Celsius
Actual melting point of p-toulic acid:  180-182 degrees Celsius

Isolating p-tert-butylphenol:
Mass of the filter paper: 0.0066 g.
Mass of the empty test tube: 5.324 g.
Mass of the dry p-tert-butylphenol, test tube, and filter paper: 5.64 g.
Mass of collected p-tert butylphenol: 0.3094 g.
Measured melting point of p-tert-butylphenol: 98.1 degrees Celsius
Actual melting point of p-tert-butylphenol:  98-101 degrees Celsius

Isolating Acetanilide
Mass of anhydrous Na₂SO_{4:  1.003 g
Mass of 100 mL test tube: 5.288g.
Mass of dry acetinilide and test tube:  5.43 g.
Mass of recovered acetinilide: 0.142 g.
Measured melting point of acetanilide:  88.9 degrees Celsius
Actual melting point of acetinilide: 113-115 degrees Celsius}