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Aldol Reaction Lab Questions

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Question 1:

In the reaction of

4-Nitrobenzaldehyde + Acetophenone -> trans-4-Nitrochalcone

a. The yield of the reaction to form your chalcone is not quantitative. What side
products might be formed from your aldol condensation?

b. If one uses benzaldehyde rather than p-nitrobenzaldehyde in the aldol reaction the yield is extremely low, if it works at all. Offer an explanation for this result.

Question 2:

In the bromination of

trans-4-Nitrochalcone -> erythro 2,3 dibromo 3-(4-nitrophenyl) propiophenone

a racemic mixture forms

a. Draw the structure of the enantiomers you form and assign R, and S to each of the

b. Will you see 2 spots on a TLC of your reaction products? Why or why not?

c. Is your bromination reaction stereoselective? Why or why not?

Question 3:

Question 4:

When you had to form a photochromic imine you had to use ammonium bromide instead of HBr. Give 2 reasons why you cannot use concentrated HBr.

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Solution Summary

Aldol reactions are analyzed. Racemic mixture forms are examined.

See Also This Related BrainMass Solution

Organic Chemistry: Aldol Condensation and Reduction of Carbonyl

See the attachments.
(Post Lab Questions: pp. 622-623, Problems 2, 5, 10)

2. Explain why the main reaction between acetophenone and p-anisaldehyde is the mixed-aldol reaction rather than (a) self-condensation of acetophenone or (b) the Cannizzaro reaction of p-anisaldehyde.

5. Propose a synthesis of cinnamaldehyde using a mixed-aldol condensation reaction.

10. Consider the spectral data for acetophenone.
a. In the functional group region of the IR spectrum, specify the absorptions associated with the carbonyl group and the aromatic ring.
b. In the 1H NMR spectrum, assign the various resonances to the hydrogen nuclei responsible for them.
c. For the 13C NMR data, assign the various resonances to the carbon nuclei responsible for them.

(Post Lab Questions: pp. 584-585, Problems 2, 3, 6, 11)

2. After the reaction between sodium borohydride and the ketone is complete, the reaction mixture is treated with water and acid to produce the desired secondary alcohol. Explain this reaction by indicating the source of the hydrogen atom that ends up on the oxygen atom.
3. Sodium borohydride is fairly unreactive toward methanol, but adding a mineral acid to this solution results in the rapid destruction of the sodium borohydride. Explain.
6. Suggest a structure for the white precipitate formed in the reaction of 9-fluorenone with sodium borohydride.
11. A nitro group, a carbon-carbon double bond, a carbon-nitrogen double bond, and an aromatic ring may each be reduced under certain conditions. Rank these functional groups in order of increasing reactivity.

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