Quiz - Alpha Carbon Chemistry - 1 | Enols and Enolates - Alpha Carbon Chemistry

Organic Chemistry 3 - Quiz - Alpha Carbon Chemistry - 1


Which of the following reagents can deprotonate a hydrogen on a carbon in the α position of a carbonyl?

H on an α-carbon of a carbonyl has a pKa ~ 16-18 (aldehyde) and ~ 19-21 (ketone). Et3N (pKa = 10.8), NaOH (pKa = 15.7) and CH3COO- (pKa = 4.76) are not strong enough to deprotonate this species unlike LDA (pKa = 36)


What is the product of the acid catalyzed reaction between Br2 and propanone?


Which of the following statements is incorrect about an enolate ion?

An enolate is actually a good nucleophile, not an electrophile. Enolates are formed by deprotonation of an α-carbon adjacent to a carbonyl group, resulting in a resonance-stabilized structure with a negative charge on the oxygen atom. This makes the enolate ion nucleophilic, as it can donate its electron pair to an electrophilic center in a chemical reaction.


Which of the following statements about keto-enol equilibrium is correct?

Carbonyls are in equilibrium with their enol forms (10 kcal.mol-1 less stable). This equilibrium can be catalyzed by a base or by an acid


Which of the following molecules is the most acidic?

The lower the pKa value, the stronger the acid. Thus, β-diketone with pKa = 9, has the lowest value and the most acidic. Followed by aldehyde with pKa approximately equal to 16-18; ketone with pKa approximately equal to 19-21; and ester with pKa approximately equal to 25.


What is tautomerization in organic chemistry?

Tautomerization is a chemical process where a molecule transforms into an isomeric form, called a tautomer, through the migration of a proton and rearrangement of electrons. The most common types are keto-enol and imine-enamine tautomerism. In keto-enol tautomerism, a carbonyl compound can convert to an enol form, while imine-enamine tautomerism involves interconversion between an imine and an enamine.


What reagent is oxidized in a haloform reaction?

The haloform reaction is commonly used to oxidize methyl ketones to carboxylic acids.


What is the primary purpose of alkylation via enolate ions in organic chemistry?

Alkylation via enolate ions is a method used to introduce an alkyl group onto a carbonyl compound, such as a ketone or an aldehyde.


What role does the base play in Malonic Ester Synthesis?

The base used in Malonic Ester Synthesis deprotonates the α-carbon of diethyl malonate to generate the corresponding enolate, which then undergoes alkylation.


What is the final step in Acetoacetic Ester Synthesis after alkylation?

After alkylation, the intermediate undergoes hydrolysis followed by decarboxylation to yield the desired α-substituted ketone or β-ketoester.