Question

1. How does a base such as NaOH help to catalyze the benzoin condensation when thiamine is present? 2. Suggest reasons why benzoic acid impurity in the benzaldehyde may drastically reduce the yield of the thiamine-promoted condensation of benzaldehyde. 3. More NaOH solution could both catalyze the condensation and neutralize the benzoic acid present if old benzaldehyde were used in the synthesis of benzoin. Unfortunately, too much base catalyzes the formation of noxious hydrogen sulfide. Where does the hydrogen sulfide come from? 4. What modifications in the reaction conditions would be necessary if an enzyme were used to catalyze the reaction? 5. Why is hydrochloric acid added to the reaction mixture for reduction of benzoin with NaBH4 after the reduction is complete?

          1. How does a base such as NaOH help to catalyze the benzoin condensation when thiamine is present?
2. Suggest reasons why benzoic acid impurity in the benzaldehyde may drastically reduce the yield of the thiamine-promoted condensation of benzaldehyde.
3. More NaOH solution could both catalyze the condensation and neutralize the benzoic acid present if old benzaldehyde were used in the synthesis of benzoin. Unfortunately, too much base catalyzes the formation of noxious hydrogen sulfide. Where does the hydrogen sulfide come from?
4. What modifications in the reaction conditions would be necessary if an enzyme were used to catalyze the reaction?
5. Why is hydrochloric acid added to the reaction mixture for reduction of benzoin with NaBH4 after the reduction is complete?

Added by Amy W.

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