9. A junior chemist was attempting to make the o unsaturated ketone 1 by a mixed
ID: 492424 • Letter: 9
Question
9. A junior chemist was attempting to make the o unsaturated ketone 1 by a mixed Aldol condensation. He instead obtained a mixture of 1 and 2, which made his boss very unhappy. When asked what conditions were employed, the chemist told his boss that he dissolved the starting materials in ethanol and then added sodium ethoxide at 25 C. The boss shook her head disappointingly and told the junior chemist that he had two days to figure it out or he was fired. Help him out! First, determine Second, propose four changes that should be made to obtain 1 as the major product. what carbonyl compounds he started with. Third, explain what effect each change is having on the reaction energy profile.Explanation / Answer
9. Mixed aldol condensation reaction,
The chemist started with acetophenone and then isobutyraldehyde. The two products he obtained were (1) from the mixed aldol condensation and (2) by self-condensation of acetophenone.
the changes the chemist must do to obtain the (1) as the only product in the reaction would be,
1) Use isobutyraldehyde in larger excess so it forces the reaction to completion.
2) The enolate of acetophenone is generated in a sea of aldehyde for immediate reaction.
3) The reaction may be carried out at low temperature wherein the enolate of acetophenone is generated at first and then reacted slowly with the aldehyde
4) The enolate may be generated slowly on the side and added to the aldehyde for reaction to get absolute selectivity.
The enolate formed by these methods would be reactive and aldehyde is more electrophilic to get attacked by enolate immediately as it come sin contact.
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