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Chapter 5: Problem 28

Carbanion intermediate is involved in (a) Perkin reaction (b) Friedel-Crafts reaction (c) Cannizzaro reaction (d) Aldol condensation

Short Answer

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(a) Perkin reaction (b) Friedel-Crafts reaction (c) Cannizzaro reaction (d) Aldol condensation Answer: (d) Aldol condensation

Step by step solution

01

Understand the concept of a carbanion

A carbanion is an anion in which carbon has a negative charge due to the presence of eight valence electrons around the carbon atom (three unshared electron pairs and one unshared electron). Carbanions are highly reactive intermediates in organic reactions.
02

Review the Perkin reaction mechanism

The Perkin reaction is an organic reaction in which an aromatic aldehyde reacts with an anhydride in the presence of an alkali salt (usually sodium acetate) to form a cinnamic acid derivative. The reaction mechanism involves the formation of an acyl anion, not a carbanion. It proceeds by nucleophilic attack, acyl migration, and subsequent dehydration.
03

Review the Friedel-Crafts reaction mechanism

The Friedel-Crafts reaction is an electrophilic aromatic substitution reaction in which an alkyl or acyl group attached to an electron-deficient compound (usually a halide) reacts with an aromatic ring to form a substituted product. Carbocations, not carbanions, are formed in this reaction type.
04

Review the Cannizzaro reaction mechanism

The Cannizzaro reaction is a redox reaction in which an aldehyde (without any α-hydrogen) is converted to a carboxylic acid and an alcohol in the presence of a strong base. The reaction involves a hydride ion transfer and does not involve carbanion intermediates.
05

Review the Aldol condensation mechanism

The Aldol condensation is a reaction between an enolizable aldehyde or ketone and an aldehyde or ketone in the presence of a base or an acid. It involves the formation of an enolate ion, which is a carbanion-like intermediate, after abstraction of a proton from the α-carbon by the base. Then, nucleophilic attack on a carbonyl group occurs, followed by dehydration to form an α,β-unsaturated carbonyl compound. Since the Aldol condensation involves a carbanion-like intermediate, the correct answer is: (d) Aldol condensation

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Most popular questions from this chapter

Statement 1 All aldehydes and ketones react with HCN to give a racemic mixture of the corresponding cyanohydrin. and Statement 2 Cyanide ion is an ambident nucleophile.

The IUPAC name of is CCC(C=O)CC(C)C (a) 2 -ethyl-4-methylpentanal (b) 4 -methyl 2 -ethylpentanal (c) 2 -methylhexanal (d) 2 -ethylhexanal

Wolff-Kishner reduction of benzophenone gives (a) benzene (b) toluene (c) diphenylmethane (d) ethylbenzene

The increasing order of the rate of HCN addition to the following carbonyl compounds is O=Cc1ccccc1 O=Cc1cccc(Cl)c1 \(\mathrm{Ph}-\mathrm{CO}-\mathrm{Ph}\) (IV) (II) (III) (a) II > IV < III < I (b) IV \(<\) II \(<\) III \(<\mathrm{I}\) (c) \(\mathrm{IV}<\mathrm{I} \leq \mathrm{III}<\mathrm{II}\) (d) \(\quad \mathrm{IV}<\mathrm{III}<\mathrm{II}<\mathrm{I}\)

Terephthalic acid is obtained by the oxidation of ( \(\mathrm{X}\) ) with acidified \(\mathrm{K}_{2} \mathrm{Cr}_{2} \mathrm{O}_{r^{*}}(\mathrm{X})\) is (a) ortho xylene (b) meta xylene (c) para xylene (d) ethylbenzene
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