Concept explainers
(a)
Interpretation: The product of Perkin condensation has to be written
Concept introduction: For the given condensation reactions,
In first case, acetic anhydride is treated with a base and a proton is abstracted. The enolate ion thus formed attacks carbonyl carbon of benzaldehyde. Loss of water molecule results in the formation of the product of Perkin condensation.
In second case, water is added to the product of Perkin condensation and it causes hydrolysis of the ester to form an acid.
In third case, diethyl malonate is treated with a base and enolate ion is formed. Enolate ion attacks a molecule of benzaldehyde and forms an intermediate species. Loss of a water molecule results in the formation of the product of Knoevenagel reaction.
In fourth case, the product of Knoevenagel reaction on acidic hydrolysis gives
(b)
Interpretation: The compound formed after addition of water to the product of Perkin condensation has to be written.
Concept introduction: For the given condensation reactions,
In first case, acetic anhydride is treated with a base and a proton is abstracted. The enolate ion thus formed attacks carbonyl carbon of benzaldehyde. Loss of water molecule results in the formation of the product of Perkin condensation.
In second case, water is added to the product of Perkin condensation and it causes hydrolysis of the ester to form an acid.
In third case, diethyl malonate is treated with a base and enolate ion is formed. Enolate ion attacks a molecule of benzaldehyde and forms an intermediate species. Loss of a water molecule results in the formation of the product of Knoevenagel reaction.
In fourth case, the product of Knoevenagel reaction on acidic hydrolysis gives carboxylic acid and on heating undergoes decarboxylation.
(c)
Interpretation: The product of Knoevenagal condensation has to be written
Concept introduction: For the given condensation reactions,
In first case, acetic anhydride is treated with a base and a proton is abstracted. The enolate ion thus formed attacks carbonyl carbon of benzaldehyde. Loss of water molecule results in the formation of the product of Perkin condensation.
In second case, water is added to the product of Perkin condensation and it causes hydrolysis of the ester to form an acid.
In third case, diethyl malonate is treated with a base and enolate ion is formed. Enolate ion attacks a molecule of benzaldehyde and forms an intermediate species. Loss of a water molecule results in the formation of the product of Knoevenagel reaction.
In fourth case, the product of Knoevenagel reaction on acidic hydrolysis gives carboxylic acid and on heating undergoes decarboxylation.
(d)
Interpretation: A compound formed after product of Perkin condensation is heated in an acidic medium has to be written
Concept introduction: For the given condensation reactions,
In first case, acetic anhydride is treated with a base and a proton is abstracted. The enolate ion thus formed attacks carbonyl carbon of benzaldehyde. Loss of water molecule results in the formation of the product of Perkin condensation.
In second case, water is added to the product of Perkin condensation and it causes hydrolysis of the ester to form an acid.
In third case, diethyl malonate is treated with a base and enolate ion is formed. Enolate ion attacks a molecule of benzaldehyde and forms an intermediate species. Loss of a water molecule results in the formation of the product of Knoevenagel reaction.
In fourth case, the product of Knoevenagel reaction on acidic hydrolysis gives carboxylic acid and on heating undergoes decarboxylation.
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Organic Chemistry (8th Edition)
- The Knoevenagel condensation reaction is a variant of the aldol reaction. A major drawback of the aldol reaction is self-aldehyde condensation. Identify the starting material in the Knoevenagel reaction that suppresses self-condensation and explainyour choice.arrow_forward9. What type of product results when an aldehyde undergoes an aldol reaction with heat? a. conjugated diene b. B-hydroxy aldehyde c. a,ß-unsaturated aldehyde d. B-ketoesterarrow_forwardWhich statement describes why aldol reactions with ketones are low yielding? A.Ketones do not have acidic protons. B.Ketones are too electron poor at the carbonyl carbon. C.Ketones can attack other ketones well but perform poorly in self-condensations. D.The product of a ketone addition to a ketone has considerable steric strain.arrow_forward
- $7. What is the major product of this intramolecular aldol condensation reaction? HO H. d. H.arrow_forward7. When the following ketone is treated with sodium hydroxide, two different enolates can form. a. Draw the two enolates, including an arrow pushing mechanism for their formation and any relevant resonance structures. NaOH b. Which enolate is favored when using sodium hydroxide as the base? Explain. c. Predict the product of the reaction and include an arrow-pushing mechanism. 1. NaOH 2. Brarrow_forwardWhat functional group is formed as the final product of an aldol condensation? A. B-hydroxycarbonyl В. a,B-unsaturated carbonyl C. enol D. enolatearrow_forward
- 4. Draw the aldehydes needed to prepare the compound below by an aldol reaction. OH CHO From: ogynu abmu and Voarrow_forward3. Draw the step-by-step mechanisms for the following reactions: a) Step 1 of the aldol condensation OH NaOEt, ETOHarrow_forwardGive the reaction mechanism for the following: a. Aldol condensation b. Claisen condensation c. Dehydration of aldol i. in basic medium ii. in acidic mediumarrow_forward
- Explain how the Knoevenagel condensation is a variant of the aldol condensation.Draw reaction schemes to answer the question.arrow_forwardWhy is the Aldol reaction often called an Aldol condensation? 1) The initially formed b-hydroxy carbonyl compound loses an oxygen atom 2) The initially formed b-hydroxy carbonyl compound loses a hydrogen atom 3) The initially formed b-hydroxy carbonyl compound loses water 4) The initially formed b-hydroxy carbonyl compound loses a hydroxyl grouparrow_forwardDraw the major product of this aldol condensation reaction. Ignore inorganic byproducts. + H H 1. NaOH, heat 2. Neutralizing work-up Drawing く a aarrow_forward
- Organic Chemistry: A Guided InquiryChemistryISBN:9780618974122Author:Andrei StraumanisPublisher:Cengage Learning