Which of these is the final product for an aldol condensation if heated?

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BlackTom AI · Accepted Answer

Question restatement: Which of these is the final product for an aldol condensation if heated?

Option 1: alkyl oxonium ion. This is not related to aldol condensation; it represents a protonated ether-like species, not a carbonyl-ene product formed in aldol chemistry. Therefore, this choice is incorrect.

Option 2: enolate ion. The enolate is an intermediate formed when a base abstracts an α-hydrogen; it participates in the aldol mechanism but is not the final product after heating. Hence, this is incorrect as the final product.

Option 3: iminium ion. Iminium ions arise in reactions like enamine or Shapiro-type processes, not as the direct dehydrated product of an aldol condensation. This is not the correct final product here.

Option 4: alpha-hydroxycarbonyl. This structure corresponds to the simple aldol addition product (the β-hydroxy carbonyl) before any dehydration. Since the question specifies the product if heated (i.e., after dehydration), this is not the final product.

Option 5: beta-hydroxycarbonyl. This is the β-hydroxycarbonyl compound formed immediately after the aldol addition step. However, upon heating, this compound typically undergoes dehydration to form the conjugated enone. Thus, while important, it is not the final dehydrated product.

Option 6: gamma-hydroxycarbonyl. This species is not a standard product in the conventional aldol condensation sequence and does not represent the expected dehydration product. Therefore, it is incorrect.

Option 7: alpha,beta-unsaturated carbonyl. This is the hallmark final product of an aldol condensation when dehydration occurs upon heating: a conjugated enone (an α,β-unsaturated carbonyl compound). This correctly matches the dehydrated, thermodynamically favored outcome.

Option 8: beta,gamma-unsaturated carbony. This designation does not correspond to the typical aldol dehydration product; the canonical conjugated system from an aldol condensation is α,β-unsaturated, not β,γ-unsaturated. This makes it incorrect.

Option 9: none of these. Since option 7 correctly describes the dehydrated product, this statement is false.

Summary explanation: In an aldol condensation, heating promotes dehydration of the initial β-hydroxy carbonyl product to yield a conjugated α,β-unsaturated carbonyl compound. The correct final product is therefore the alpha,beta-unsaturated carbonyl. The other options either represent intermediates (enolate, β-hydroxycarbonyl, α-hydroxycarbonyl), unrelated intermediates (alkyl oxonium, iminium), or incorrect unsaturation positioning (β,γ-unsaturated), or the null option which is contradicted by the presence of a correct choice.

CHE 008B A01 SS1 2025 Lecture 9 - Reactions of Enolate Ions

Which of these is the final product for an aldol condensation if heated?

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