CHE 317  " Recrystallization"

Interpretation of Results and the Report

The results of the mixture-melting-point determinations should be presented in tabular form.  List all of the possibilities tested and the corresponding measurements in such a way that your conclusions are obvious from your experimental results.

1.  As before: Your Name

                        Date

                        CHE 317

                        Unknown #

2.  In your own words, explain what recrystallization is and how it works to separate solid compounds.  Describe how the appropriate solvent is selected for recrystallization.

3.  In a few sentences, summarize what you did in this experiment, be specific.

4.  Make a table:

     weight of the unknown       g

     weight of product       g

     observed melting range of unknown

     list of possible compounds and their literature

     mp's, and the observed mixed mp's with your product.

5.  Conclusion as to the identity of the product. Justify your answer.

6.  How pure do you think the product is? Explain?

7.  Answer the following questions:

a)  For the following reported melting points, comment on the purity of the sample:

78-79 ^oC

299-301 ^oC

178 ^oC decomposes

137-149 ^oC

b)   If, in any recrystallization, an "oil" (liquid phase) comes out of solution rather than a solid, why did this happen?  What can you do about it?

c)  What happens in this experiment if more than the minimum of hot solvent is used in the recrystallization?

d)  What was the purpose of the hot filtration?  Why didn’t you use gravity or suction filtration at this point?

e)  In the CRC Handbook, look up 1-bromo-2-nitrobenzene (look under benzene) and list the mp, crystal form, and the solvent used in the recrystallization of this compound.

 
Attach the carbons from your notebook.

© Dr. Noel Sturm 2009