Organic Chemistry-III: Claisen & Mannich Reactions
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Questions and Answers

What is the primary product formed in a crossed Claisen condensation?

  • β-keto-ester (correct)
  • aldehyde
  • diketone
  • α-carbanion

    • Which of the following bases is used in Claisen condensation to generate the α-carbanion?

  • LiAlH4
  • NaOH
  • sodium alkoxide (correct)
  • K2CO3

    • In the mechanism of the Mannich reaction, which nucleophile plays a crucial role?

  • α-carbanion
  • ketone
  • iminium ion (correct)
  • alkoxide ion

    • What type of reaction results when using a base to condense two ester molecules?

    <p>Claisen condensation</p> Signup and view all the answers

    Which reaction is characterized by the formation of β-keto-esters?

    <p>Crossed Claisen condensation</p> Signup and view all the answers

    In which scenario will an α-carbanion not be generated when reacting an ester?

    <p>Using sodium alkoxide as the base</p> Signup and view all the answers

    What is the primary purpose of the Claisen reaction in organic chemistry?

    <p>To generate carbon-carbon bonds</p> Signup and view all the answers

    What drives the completion of the Dieckmann condensation?

    <p>Removal of a proton from the ester product by base</p> Signup and view all the answers

    Which compound is formed as a result of the Mannich reaction?

    <p>β-amino-carbonyl compound</p> Signup and view all the answers

    In the synthesis of steroids, which elements are crucial in the Dieckmann condensation process?

    <p>Lithium ethyl anilide and high dilution techniques</p> Signup and view all the answers

    What is the primary role of sodium alkoxide in Claisen condensation?

    <p>It generates the α-carbanion necessary for the reaction.</p> Signup and view all the answers

    What type of reaction does the Mannich reaction exemplify?

    <p>Nucleophilic addition followed by dehydration</p> Signup and view all the answers

    Which of the following correctly describes the product formed in a Claisen condensation?

    <p>A β-keto ester.</p> Signup and view all the answers

    In the Mannich reaction, which components are necessary for the formation of a Mannich base?

    <p>A secondary amine, formaldehyde, and an enolizable aldehyde or ketone.</p> Signup and view all the answers

    What is a major application of the Dieckmann reaction?

    <p>Formation of cyclopentanone and cyclohexanone derivatives</p> Signup and view all the answers

    What is a consequence of using formaldehyde in a mixed aldol condensation?

    <p>It can lead to extra unwanted reactions.</p> Signup and view all the answers

    What differentiates Claisen condensation from regular aldol condensation?

    <p>Claisen condensation involves two esters instead of aldehydes or ketones.</p> Signup and view all the answers

    During the Claisen condensation, what can happen if hydroxide ion is used instead of alkoxide ion?

    <p>The ester will undergo hydrolysis instead of condensation.</p> Signup and view all the answers

    What type of reaction is the Dieckmann condensation considered to be?

    <p>A variation of Claisen condensation with diesters.</p> Signup and view all the answers

    What is the characteristic feature of formaldehyde that makes it an ideal electrophilic partner?

    <p>It cannot enolize.</p> Signup and view all the answers

    What is the first step in both Claisen and aldol reactions?

    <p>Formation of a carbanion via abstraction of α-hydrogen.</p> Signup and view all the answers

    What is the final product of the Claisen condensation reaction?

    <p>Dimers of the original carbon chain</p> Signup and view all the answers

    What role does the enolate ion play in both the aldol reaction and the Claisen condensation?

    <p>It acts as a nucleophile.</p> Signup and view all the answers

    What is a significant difference in the mechanism between Claisen condensation and aldol addition after the nucleophilic attack?

    <p>The negatively charged oxygen reforms a carbon-oxygen double bond.</p> Signup and view all the answers

    What is the primary purpose of the crossed Claisen condensation involving ethyl benzoate?

    <p>Synthesis of flavones</p> Signup and view all the answers

    Why must the alkoxide ion used in the Claisen reaction be the same as that of the alcohol part of the ester?

    <p>To prevent the formation of byproducts through trans-esterification.</p> Signup and view all the answers

    Which of the following natural products can be synthesized using ethyl formate in a crossed Claisen condensation?

    <p>Thiamine (Vitamin B1)</p> Signup and view all the answers

    What must occur in the Claisen condensation for the reaction to be driven to completion?

    <p>A proton must be removed from the β-keto ester.</p> Signup and view all the answers

    What type of derivatives are formed when ketones and esters undergo condensation with diethyl oxalate?

    <p>Oxalyl derivatives</p> Signup and view all the answers

    Which type of reaction does the Claisen condensation represent?

    <p>Nucleophilic substitution reaction.</p> Signup and view all the answers

    What happens to the negatively charged oxygen in the aldol addition step?

    <p>It obtains a proton from the solvent.</p> Signup and view all the answers

    In the mechanism of Dieckmann condensation, which of the following statements is true?

    <p>It utilizes an intramolecular process.</p> Signup and view all the answers

    How do the products of Claisen condensation and aldol addition differ?

    <p>They both have carbonyl groups but differ in structure.</p> Signup and view all the answers

    Which compound can be synthesized from diethyl-α-oxalyl phenyl acetate upon hydrolysis and heating?

    <p>α-keto acids</p> Signup and view all the answers

    During the crossed Claisen condensation with ethyl benzoate, which of the following compounds is notably not formed?

    <p>Aromatic aldehydes</p> Signup and view all the answers

    What effect does the presence of an alkoxide ion have in the Claisen condensation process?

    <p>It drives the reaction toward the formation of products.</p> Signup and view all the answers

    What characterizes the products of both Claisen condensation and aldol addition in their molecular structure?

    <p>They both have carbonyl groups at the end of the chain.</p> Signup and view all the answers

    What distinguishes the mechanism of Dieckmann condensation from that of typical Claisen condensation?

    <p>Dieckmann has intramolecular processes.</p> Signup and view all the answers

    Which application of Claisen condensation is directly linked to the synthesis of nicotine?

    <p>With ethyl nicotinate</p> Signup and view all the answers

    What is one of the synthetic applications of phenyl substituted malonic ester?

    <p>Synthesis of phenobarbitone</p> Signup and view all the answers

    Which type of ester is typically involved in the Dieckmann reaction?

    <p>1,6-diester</p> Signup and view all the answers

    Study Notes

    Subject Matter

    • Chemistry Module on Claisen and Mannich Reactions

    Paper Number and Title

    • Paper 9: Organic Chemistry-III (Reaction Mechanism-2)

    Module Number and Title

    • Module 20: Claisen condensation and Mannich reaction

    Module Tag

    • CHE_P9_M20

    Learning Outcomes

    • Students will understand the basics of Claisen and Mannich reactions
    • Can identify major products in crossed Claisen condensation and Dieckmann reactions
    • Can evaluate and apply mechanistic details of reactions
    • Understand applications of these reactions

    Introduction

    • Aldol condensation joins aldehydes/ketones with a-hydrogens using a base (e.g., NaOH)
    • Claisen condensation is the aldol reaction applied to esters
    • It uses alkoxide (e.g., sodium alkoxide) as base instead of hydroxide to avoid ester hydrolysis
    • Dieckmann condensation is Claisen condensation with diesters, forming cyclic B-keto esters

    Claisen Condensation

    • A carbon-carbon bond forming reaction between two esters
    • Occurs in the presence of sodium alkoxide as a base
    • Produces a β-keto ester as the product

    Mixed Claisen Condensation

    • Reaction between two different esters
    • Can form complex mixtures of products
    • Less synthetically valuable unless one reactant has no α-hydrogen

    Dieckmann Condensation

    • Intramolecular Claisen reaction
    • Occurs with diesters, forming five-membered ring esters

    Mannich Reaction

    • Alkylation of carbonyl compounds with formaldehyde and primary/secondary amines
    • Forms β-amino carbonyl compounds (Mannich bases)

    Asymmetric Mannich Reactions

    • Uses chiral catalysts (e.g., proline) to control stereochemistry
    • Creates enantiomers of Mannich products

    Applications of Claisen Condensation

    • Synthesis of various compounds (e.g., vitamins, sex hormones)
    • Condensation reactions with ethyl benzoate, synthesis of flavones (chrysin), etc.

    Applications of Dieckmann Reaction

    • Synthesis of cyclopentanone and cyclohexanone derivatives
    • Preparation of heterocyclic ketoesters

    Applications of Mannich Reaction

    • Synthesis of natural compounds (e.g., peptides, nucleotides, antibiotics)
    • Synthesis of medicinal compounds (e.g., rolitetracycline, fluoxetine, tramadol)

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    Organic Reaction Mechanisms PDF

    Description

    Explore the fundamentals of Claisen and Mannich reactions in this quiz designed for Paper 9 of Organic Chemistry-III. Understand the mechanisms, identify major products, and evaluate the applications of these important organic reactions. Perfect for students looking to enhance their knowledge of reaction mechanisms.

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