Free Practice Quiz Question List

06 Enols, Enolates, and Carbon–Carbon Bond Formation Online Quiz Questions

Use this free practice quiz with 20 questions to review 06 Enols, Enolates, and Carbon–Carbon Bond Formation, test your knowledge, and prepare for your next test or exam.

20 questions

True or false

1 point

True or false: α hydrogens are more acidic than ordinary alkane hydrogens because their removal can form a resonance-stabilized species.

A
True
B
False

Choose one

1 point

In acid-catalyzed enolization of a carbonyl compound, which sequence of steps occurs?

A
An α proton is removed, then the carbonyl oxygen is protonated.
B
The carbonyl oxygen is protonated, then an α proton is removed.
C
The carbonyl carbon is protonated, then an α proton is removed.
D
An α proton is removed, then the carbonyl carbon is deprotonated.

Choose one

1 point

A carbonyl compound has nonequivalent α positions. Which conditions often favor formation of its kinetic enolate?

A
Reversible enolization at conditions that allow equilibration.
B
Heating until the most stable enolate is the only possible product.
C
Rapid deprotonation with a strong, bulky base at low temperature.
D
Protonating the carbonyl oxygen before adding a nucleophile.

Fill in the blank

1 point

In a Michael addition, an enolate donor forms a new C–C bond by attacking the of an α,β-unsaturated carbonyl compound. The new bond joins that site to the donor’s .

Choose all

1 point

Which two strategies can improve selectivity in a crossed aldol reaction? Select all that apply.

A
Use an acceptor with no α hydrogens alongside a carbonyl compound that can form an enolate.
B
Use two different carbonyl compounds that both form enolates, without controlling which one forms.
C
Preform one enolate with a strong base, then add the chosen electrophile.
D
Use conditions that deliberately allow both carbonyl partners to form many competing enolates.

True or false

1 point

True or false: In the common base-promoted E1cB dehydration of a β-hydroxy carbonyl, the β-hydroxyl group leaves before the α carbon is deprotonated.

A
True
B
False

Fill in the blank

1 point

In an aldol reaction, the new carbon–carbon bond connects the .

Choose one

1 point

Which description identifies a Claisen condensation?

A
An ester enolate adds to an aldehyde and gives a β-hydroxy carbonyl without loss of a leaving group.
B
An ester enolate attacks another ester, the intermediate expels an alkoxide, and a β-keto ester results.
C
An enolate attacks the β carbon of an α,β-unsaturated carbonyl and gives a conjugate-addition product.
D
An enolate substitutes at the α carbon of a primary alkyl halide to give an α-alkylated carbonyl.

Written response

1 point

Cyclohexanone is treated with LDA and then methyl iodide. What is the name of the resulting α-methylated ketone?

Written response

1 point

When reversible enolization allows equilibration, what feature of the C=C bond often characterizes the thermodynamic enolate?

Choose all

1 point

Which two statements are consistent with using an enolate for α-alkylation? Select all that apply.

A
A primary alkyl halide is generally a suitable electrophile for enolate substitution.
B
Preforming the enolate can help limit competing aldol reactions.
C
A tertiary alkyl halide is generally preferred because it reacts readily by SN2.
D
The enolate must be generated only after the alkyl electrophile is added.

Open ended

1 point

Propose a selective crossed aldol addition using propanal and benzaldehyde to obtain a β-hydroxy carbonyl product. Identify the donor and acceptor, state why the pairing can improve selectivity, and specify which carbons form the new bond and what product class results after protonation.

Written response

1 point

What is the name of the neutral intermediate that has an –OH group attached to a carbon–carbon double bond?

Choose one

1 point

Under dilute base, two molecules of propanal undergo aldol addition without dehydration. Which product is formed?

A
2-Hydroxy-3-methylbutanal
B
3-Hydroxy-2-methylbutanal
C
3-Hydroxy-2-methylpentanal
D
2-Methylpent-2-enal

Choose one

1 point

Why are α hydrogens of a carbonyl compound more acidic than ordinary alkane hydrogens?

A
They are attached directly to the carbonyl carbon.
B
Their removal forms a resonance-stabilized species.
C
They are stabilized by a neighboring alkyl group only.
D
Their removal forms a neutral enol in every case.

Choose one

1 point

Which description best explains the reactivity of a carbonyl enolate?

A
The negative charge is localized only on the carbonyl carbon.
B
The negative charge is shared between the carbonyl oxygen and the carbonyl carbon.
C
The negative charge is distributed between oxygen and the α carbon, and reaction commonly occurs at the α carbon.
D
The enolate is neutral and reacts only through oxygen.

Choose one

1 point

A ketone has nonequivalent α positions. Which conditions often favor formation of its kinetic enolate?

A
Use a strong, bulky base at low temperature and deprotonate rapidly.
B
Use reversible conditions that allow the enolates to equilibrate.
C
Heat the mixture until the more substituted alkene is favored.
D
Use a weak acid to protonate the carbonyl oxygen.

Choose one

1 point

In an aldol reaction, which pair of atoms forms the new carbon–carbon bond?

A
The donor's carbonyl oxygen bonds to the acceptor's α carbon.
B
The donor's carbonyl carbon bonds to the acceptor's carbonyl oxygen.
C
The donor's α carbon bonds to the acceptor's α carbon.
D
The donor's α carbon bonds to the acceptor's carbonyl carbon.

True or false

1 point

In a Claisen condensation, an ester enolate attacks another ester, and expulsion of an alkoxide leads to a β-keto ester.

A
True
B
False

Written response

1 point

In a Michael addition, to which position of the α,β-unsaturated carbonyl compound does the enolate add?