Free Practice Quiz Question List

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

Use this free practice quiz with 20 questions to review 11 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: An α-hydrogen in propanone is more acidic than an ordinary alkane hydrogen because its removal produces a resonance-stabilized enolate.

A
True
B
False

Choose one

1 point

Why are the keto and enol forms of a carbonyl compound constitutional isomers rather than resonance forms?

A
They are resonance contributors because only electrons move.
B
They are constitutional isomers because a hydrogen and a double bond change position.
C
They are conformers because a single bond rotates.
D
They are enantiomers because the carbonyl group becomes chiral.

Choose one

1 point

In enolate alkylation with a suitable alkyl halide, which event forms the new carbon–carbon bond?

A
The enolate’s α-carbon attacks the alkyl halide and displaces its leaving group.
B
The enolate oxygen attacks the alkyl halide and forms an O–C bond.
C
The alkyl halide’s leaving group attacks the enolate’s carbonyl carbon.
D
The enolate’s carbonyl carbon attacks the alkyl halide by electrophilic addition.

Choose all

1 point

Which alkyl halide classes are best suited for enolate alkylation by the S_N2 mechanism? Select all correct choices.

A
Methyl alkyl halides
B
Primary alkyl halides
C
Tertiary alkyl halides

Written response

1 point

What is the approximate pKa of an α-hydrogen in propanone?

True or false

1 point

True or false: An aldol reaction requires at least one of its carbonyl partners to have an α-hydrogen so that an enol or enolate donor can form.

A
True
B
False

Choose one

1 point

What structural feature characterizes the carbonyl product formed when an aldol addition product undergoes dehydration?

A
A saturated carbonyl compound with an extra hydroxyl group
B
An unconjugated alkene separated from the carbonyl by a saturated carbon
C
A conjugated α,β-unsaturated carbonyl compound
D
An enolate ion with no carbon–carbon double bond

Choose all

1 point

Which statements describe strategies or outcomes relevant to controlling a crossed-aldol reaction? Select all correct choices.

A
Choosing one partner to form the enolate selectively can favor a single crossed-aldol product.
B
A carbonyl compound with no α-hydrogen cannot form an enolate and may serve as the electrophile.
C
If both partners can form enolates, a single crossed-aldol product is guaranteed.
D
A partner with α-hydrogens can be selected to form the enolate while the other acts mainly as the electrophile.

Written response

1 point

What is the IUPAC name of the β-hydroxy aldehyde formed by the aldol addition of two ethanal molecules?

Open ended

1 point

Describe the three main steps of the base-catalyzed aldol addition mechanism, identifying how the new carbon–carbon bond forms and how the catalyst is regenerated.

Choose one

1 point

Which description best characterizes an intramolecular aldol reaction?

A
An enolate attacks the carbonyl of a separate molecule, joining two molecules.
B
An enolate at one site attacks another carbonyl in the same molecule, often closing a ring.
C
A carbonyl compound tautomerizes to an enol without forming a new carbon–carbon bond.
D
A carbonyl compound loses water to form an alkyl halide.

Written response

1 point

An α-hydrogen in propanone has an approximate pKa of 19, while an alkane hydrogen has an approximate pKa of 60. What is the approximate difference between these pKa values?

Choose one

1 point

What best explains why the keto and enol forms of a carbonyl compound are tautomers rather than resonance forms?

A
They are resonance forms because only electrons move and no hydrogen changes position.
B
They are constitutional isomers because a hydrogen and a double bond change position.
C
They are stereoisomers because the carbonyl group rotates.
D
They are different ions formed by removal of an α-hydrogen.

True or false

1 point

In an aldol addition that creates a stereogenic center, an achiral environment commonly gives a racemic mixture when both enantiomeric pathways are equally accessible.

A
True
B
False

Choose one

1 point

A chemist wants to generate a substantial amount of enolate from a carbonyl compound. Which approach is best supported by the material?

A
A weak base always converts all of the carbonyl compound into enolate.
B
A strong base prevents enolate formation by protonating the carbonyl oxygen.
C
A strong base such as LDA can convert a carbonyl compound substantially into enolate.
D
Any base produces the same enolate amount, regardless of its strength.

Written response

1 point

What is the name of the β-hydroxy aldehyde formed by aldol addition when two ethanal molecules react?

Choose one

1 point

In a base-catalyzed aldol addition, which event forms the new carbon–carbon bond?

A
The electrophile forms an enolate, which attacks the donor’s α-carbon.
B
The donor forms an enolate, whose α-carbon attacks the electrophile’s carbonyl carbon.
C
The donor’s carbonyl oxygen attacks the electrophile’s α-hydrogen.
D
Both molecules first lose their carbonyl oxygens, then their α-carbons bond.

Choose one

1 point

When a β-hydroxy carbonyl product undergoes dehydration in an aldol condensation, what type of product results?

A
It forms a saturated carbonyl compound with no carbon–carbon double bond.
B
It converts the carbonyl group into an alcohol without changing the carbon skeleton.
C
It forms a conjugated α,β-unsaturated carbonyl compound.
D
It breaks the carbon–carbon bond formed during aldol addition.

Fill in the blank

1 point

An enolate’s negative charge is delocalized between oxygen and the .

Fill in the blank

1 point

When an enolate reacts at its α-carbon with an electrophile, replacing an α-hydrogen with a new group, the product is an .