Aldehydes and Ketones                                Name _____________________

 

Tollens’ Test (test for aldehydes)

 

I.  Write an equation for the reaction of an aldehyde with Tollens’ reagent.

 

 

 

 

 

II.  Clean 3 reaction tubes by adding a few milliliters of 10% NaOH to each and

      heating in a water bath while preparing the Tollens’ reagent.

 

III. Write a flow chart for the preparation of Tollens’ reagent.

 

 

 

 

 

 

IV.  Empty reaction tubes of NaOH and rinse.

 

V.  Write a procedure for testing the three knowns (acetophenone, benzaldehyde,

      and hexane) with Tollens’ reagent.

 

 

 

 

 

VI.  Observations

 

Tollen’s reagent plus  

acetophenone

benzaldehyde

hexane

 

 

 

 

 

 

VII.  PROMPTLY DESTROY excess TOLLENS’ REAGENT with a few drops

        of nitric acid.  It can form an explosive fulminate on standing.  A drop of

        nitric acid can be used to remove the silver mirrors form test tubes.

Schiff’s Test (a very sensitive test for aldehydes)

 

I.  Write an equation for the reaction of an aldehyde with Schiff’s reagent.

 

 

 

 

 

 

 

 

 

 

 

 

II.  Write a procedure for testing the three known substances (acetophenone,

       benzophenone, and hexane) with Schiff’s reagent.

 

 

 

 

 

 

 

III.  Observations

 

Schiff’s reagent plus

acetophenone

benzaldehyde

hexane

 

 

 

 

 

 

 

VI. Clean up

 

      Neutralize the solution with Na2CO3 and flush it down the drain.

 

 

 

 

Iodoform Test (test for methyl ketones)

 

I.  Write an equation for the reaction of a methyl ketone to form iodoform.

 

 

 

 

 

 

 

II.  Write a procedure for the iodoform test with

 

A.     a water soluble substance:

 

 

 

 

 

B.      a water insoluble substance:

 

 

 

 

 

III.  Observations

 

       Iodine solution plus

acetophenone

benzaldehyde

hexane

 

 

 

 

 

 

 

VI.  Clean up

 

       Combine all reaction mixtures in a beaker, add a few drops of acetone to

       destroy any unreacted iodine in potassium iodide reagent, remove iodoform

       by suction filtration, and place iodoform in the halogenated organic waste

       container.  The filtrate can be flushed down the drain after neutralization

       (if necessary).

Bisulfite Test (test for unhindered aldehydes or ketones)

 

I.  Write an equation for the reaction of an unhindered aldehyde or ketone

     with a sodium bisulfite solution.

 

 

 

 

 

 

 

II.  Write a procedure for the reaction of an unhindered aldehyde or ketone

      with sodium bisulfite.

 

 

 

 

 

 

 

III.  Observations

 

       NaHSO3 solution plus       

acetophenone

benzaldehyde

hexane

 

 

 

 

 

 

 

IV.  Clean up

 

       Dilute the bisulfite solution with a large amount of water and flush the mixture

       down the drain.  The amount of organic material being discarded is negligible.

 

 

 

 

 

 

 

Part 2,  Unknown

 

Your unknown may be acetophenone, benzaldehyde, n-butanal, cinnamaldehyde, 

furfural, 2-heptanone, 3-heptanone, n-heptanal, or 2-octanone.

 

Aldehyde or ketone?

 

Run a Tollens’ or/and a Schiff’s Test to determine, if you have an aldehyde or ketone.

 

Tollens’ Test

 

I.  Observations for unknown

 

Tollens’ reagent plus  

acetophenone (or hexane)

benzaldehyde

unknown

 

 

 

 

 

 

II.  DO NOT FORGET TO PROMPTLY DESTROY excess TOLLENS’

      REAGENT.

 

Schiff’s Test

 

I.  Observations for unknown

 

Schiff’s reagent plus

acetophenone (or hexane)

benzaldehyde

unknown

 

 

 

 

 

 

If you have a ketone, test to see if you have a methyl ketone

 

Results of Iodoform test:  ___________________________________

 

 

 

 

Boiling point of unknown

 

You must determine the boiling point of your unknown.  See Chapter 4, Boiling Points, In a Reaction Tube, page 75 for the procedure.

 

Boiling point of your unknown:  _____________________________

 

2,4-dinitrophenylhydrazone or semicarbazone derivative

 

You must submit one derivative of your unknown (either a

2,4-dinitrophenylhydrazone or semicarbazone derivative).  If the first derivative that you make is oily and won’t crystallize out, try making the second derivative.  You need at least one good derivative to get a melting point.

 

I recommend doubling the quantities when making the derivatives.

 

I.  Write a reaction for the preparation of the 2,4-dinitrophenylhydrazone or

     semicarbazone derivative of an aldehyde or ketone.

 

 

 

 

 

 

II.  Write a procedure for the preparation of the 2,4-dinitrophenylhydrazone or

     semicarbazone derivative of an aldehyde or ketone.

 

 

 

 

 

 

 

 

 

 

III.  Observations

 

       Melting point of 2,4-dinitrophenylhydrazone or semicarbazone derivative

        of your unknown:    _____________

Turn in the 2,4-dinitrophenylhydrazone or semicarbazone derivative of your unknown with this experiment.

 

Conclusion

 

Unknown  # _____  is _______________________________________________.

 

QUESTIONS

 

1. What is the purpose of making derivatives of unknowns.

 

 

 

 

2. Why are 2,4-dinitrophenylhydrazones better derivatives than phenylhydrazones?

 

 

 

 

3.  Using chemical tests how you distinguish among 2-pentanone, 3-pentanone,

     and pentanal?

 

 

 

 

 

4.  Draw the structure of a compound, C5H8O, that gives a positive iodoform

     and does not decolorize permanganate.

 

 

 

 

5.  Draw the structures of three different compounds, C5H8O, that give a positive

     Tollen’s test and do not react with bromine in dichloromethane.

 

 

 

 

 

 

6.  Draw the structures of five different compounds, C5H8O, that react with

     phenylhydrazine, decolorize bromine in dichloromethane, and do not give

     a positive iodoform test.

 

 

 

 

 

 

7.  Draw the structures of two geometric isomers, C5H8O, that give a positive

     iodoform test.

 

 

 

 

9.  Give the wavenumber (cm-1) of the carbonyl peak in the IR in Figure 36.4 of

     your lab text.

 

 

 

10.  Assign various peaks in the 1H NMR spectrum of 2-butanone to specific

     protons in the following molecule (See Figure 36.6 in your lab text):

 

           (a)       (b)   (c)                        quartet   2.4 PPM  _______

          CH3-C-CH2-CH3                             

                   ||                                     singlet  2.1 PPM  ________

                  O

                                                              triplet  1.0 PPM  ________

 

11.  Assign various peaks in the 1H NMR spectrum of crotonaldehyde to specific

       protons in the following molecule (see Figure 36.7 in your lab text):

 

            (a)  (b)   (c)  (d)            doublet  9.5 PPM  _______

          CH3CH=CHCHO

                                                    sextet  6.9 PPM  _______

 

                                                quartet (doublet of doublets)  6.1 PPM  _______

 

                                                doublet  2.0 PPM  _______