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    Aldol Reactions: Benzalacetophenone and Dibenzalacetone

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    "In a 125-mL Erlenmeyer flask containing a magnetic stirring bar, mix 0.05 mol of benzaldehyde with the theoretical quantity of acetone, and add one-half the mixture to a solution of 5 g of sodium hydroxide dissolved in 50 mL of water and 40 mL of ethanol at room temperature (<25oC). After 15 min of stirring, add the remainder of the aldehyde-ketone mixture and rinse the container with a little ethanol to complete the transfer. Stir the mixture for 30 min; then collect the product by suction filtration on a Buchner funnel. Break the suction and carefully pour 100 mL of water on the product. Reapply the vacuum. Repeat this process three times in order to remove all traces of sodium hydroxide. Finally, press the product as dry as possible on the filter using a cork and then press it between sheets of filter paper to remove as much water as possible. Save a small sample for a melting point determination; then recrystallize the product from ethanol using about 10 mL of ethanol for each 4 g of dibenzalacetone. The yield after recrystallization should be above 4 g.
    Cleaning Up: Dilute the filtrate from the reaction mixture with water and neutralize it with dilute hydrochloric acid before flushing down the drain."
    Using the above procedure answer the below question. Please explain your answer through illustration if necessary. Always make your explanation detailed.
    1) p. 525 #5 How would you change the procedures if you wanted to synthesize benzalacetone (C6H5CH=CHCOCH3)?
    2) How would you change the procedures if you wanted to synthesize benzalacetophenone (C6H5CH=CHCOC6H5)?
    3) Draw the three geometric isomers of dibenzalacetone. Which do you expect as the product of the reaction of 2 Benzaldehyde + acetone &#61664; dibenzalacetone and why?
    4) Show a step-by-step mechanism of 2 Benzaldehyde + acetone &#61664; dibenzalacetone?
    5) Calculate a theoretical yield using the above procedure.
    6) Show a step-by-step mechanism to make the Benzalacetone?
    7) Show a step-by-step mechanism to make benzalacetophenone?
    8) Why is it import to maintain the specified proportions of organic reagents 2 Benzaldehyde + acetone &#61664; dibenzalacetone reaction?
    9) Why is the condensation product, dibenzalacetone, formed in this reaction and not the aldol addition product, 1,5-dihydroxy-1,5-diphenylpentane-3-one?
    10) Show the complete mechanism (step-by-step) for the formation of dibenzalacetone from benzaldehyde and benzalacetoone?
    11) The normal characteristics stretching frequency of the carbonyl group of a ketone in the IR spectrum is about 1720 cm-1. Pick out the carbonyl stretching frequency of dibenzalacetone in Fig.37.6. Why is it so much lower than expected?

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    Solution Summary

    Questions regarding Aldol Reactions and the synthesis of Benzalacetophenone and Dibenzalacetone are answered in detail.