Free Practice Quiz Question List

09 Advanced Reaction Mechanisms Online Quiz Questions

Use this free practice quiz with 20 questions to review 09 Advanced Reaction Mechanisms, test your knowledge, and prepare for your next test or exam.

20 questions

True or false

1 point

A symmetry-allowed pericyclic pathway is necessarily fast and favorable under every set of reaction conditions. True or false?

A
True
B
False

Choose one

1 point

Which description best matches the bond and charge changes in a Wagner–Meerwein rearrangement?

A
A carbon–carbon bond migrates away from the carbocation, carrying the positive charge with it.
B
A carbon–carbon bond migrates toward the carbocation with its bonding electron pair, and the positive charge relocates.
C
A carbon–carbon bond breaks homolytically, producing two radicals.
D
A carbon–carbon bond migrates toward the carbocation while both bonding electrons remain behind.

Fill in the blank

1 point

In the usual E2 geometry, the breaking C–H and C–X bonds are to support orbital overlap.

Choose one

1 point

For an SN2 reaction, which combination of rate dependence and stereochemical outcome is expected?

A
The rate depends only on substrate concentration, and the reacting stereocenter retains its configuration.
B
The rate depends on both substrate and nucleophile concentrations, and the reacting stereocenter undergoes inversion.
C
The rate depends only on nucleophile concentration, and the reacting stereocenter undergoes inversion.
D
The rate is independent of both substrate and nucleophile concentrations, and the stereochemical outcome is racemization.

Written response

1 point

In a thermal Diels–Alder reaction, how many new bonds form between the diene and dienophile in the concerted step?

Choose one

1 point

A conjugated chain containing a 6π-electron system undergoes thermal electrocyclic ring closure. Which terminal motion is symmetry-allowed?

A
It closes conrotatorily because all thermal electrocyclic closures rotate in the same direction.
B
It closes disrotatorily because the terminal orbitals rotate in opposite directions.
C
It closes suprafacially because all electrocyclic reactions use suprafacial motion.
D
It closes antarafacially because a 6π-electron system requires opposite faces of the chain.

Choose all

1 point

Which observations can provide complementary experimental tests of a proposed reaction mechanism? Select all that apply.

A
A measured rate law showing which reactant concentrations affect the rate.
B
The balanced overall equation, used by itself to read off the measured rate law.
C
A kinetic isotope effect after replacing hydrogen with deuterium.
D
A stereochemical outcome that tests the geometry of the proposed pathway.

True or false

1 point

If replacing hydrogen with deuterium substantially slows a reaction, this supports significant C–H bond cleavage in the rate-controlling transition state, but does not by itself prove the full mechanism.

A
True
B
False

Written response

1 point

What is the name of the rearrangement that converts a primary amide to an amine with loss of the carbonyl carbon?

Fill in the blank

1 point

The experimentally measured relationship between reaction rate and reactant concentrations is called the .

Choose all

1 point

Which statements about sigmatropic rearrangements and rearrangement pathways are supported? Select all that apply.

A
Thermal [3,3] shifts such as the Cope and Claisen rearrangements proceed suprafacially on the participating systems.
B
A Claisen rearrangement of an allyl vinyl ether produces only a saturated alcohol.
C
A Claisen rearrangement forms a new carbon–carbon bond and an unsaturated carbonyl product.
D
A sequence of apparent rearrangement shifts can occur in separate steps rather than as one concerted event.

Choose one

1 point

Which statement describes the condition-dependent orbital-symmetry outcome for a suprafacial–suprafacial [2+2] cycloaddition?

A
A suprafacial–suprafacial [2+2] cycloaddition is favored thermally and disfavored photochemically.
B
A suprafacial–suprafacial [2+2] cycloaddition is symmetry-allowed under both thermal and photochemical conditions.
C
A suprafacial–suprafacial [2+2] cycloaddition is thermally symmetry-disfavored but can be enabled photochemically.
D
A suprafacial–suprafacial [2+2] cycloaddition cannot occur under either thermal or photochemical conditions.

Open ended

1 point

A proposed concerted mechanism appears to give the observed product. Explain how orbital compatibility, stereochemical outcomes, and kinetic evidence could each be used to test the proposal. Include why a measured rate law cannot be read directly from the overall reaction equation and why one observation alone is usually insufficient.

Choose one

1 point

A conjugated 4π-electron chain undergoes thermal electrocyclic ring closure. Which terminal-orbital rotation mode is permitted by the selection rule?

A
Disrotatorily
B
Conrotatorily
C
Suprafacially
D
Antarafacially

True or false

1 point

If orbital symmetry allows a pericyclic pathway, the reaction must be fast and favorable under any conditions.

A
True
B
False

Choose one

1 point

An elementary substitution step shows a rate proportional to both substrate and nucleophile concentrations. Which outcome is consistent with an SN2 mechanism?

A
Its rate depends only on substrate concentration, and it gives retention at the reacting stereocenter.
B
Its rate depends only on nucleophile concentration, and it gives inversion at the reacting stereocenter.
C
Its rate depends on both substrate and nucleophile concentrations, and it gives inversion at the reacting stereocenter.
D
Its rate depends on both substrate and nucleophile concentrations, and it gives retention at the reacting stereocenter.

Choose one

1 point

A proposed mechanism contains an elementary step involving two reacting species. Which approach provides a sound test of its kinetic compatibility?

A
Measure the rate law experimentally; the overall equation alone does not determine it.
B
Infer the rate law directly from the coefficients in the overall balanced equation.
C
Assume the rate depends only on the reactant present in the greatest amount.
D
Use product stereochemistry alone to assign the reaction order.

Choose one

1 point

A suprafacial–suprafacial [2+2] cycloaddition is being considered. Which statement correctly compares its thermal and photochemical behavior?

A
It is thermally symmetry-allowed, but photochemical excitation prevents it.
B
It is thermally symmetry-disfavored, but photochemical excitation can enable it.
C
It is disrotatory thermally and conrotatory photochemically.
D
It must proceed through a discrete carbocation intermediate under both conditions.

Written response

1 point

During an acid-promoted pinacol rearrangement, a protonated hydroxyl group departs as a neighboring group migrates. What molecule is expelled?

Written response

1 point

In a 1,2-shift toward a neighboring electron-deficient center, what moves along with the migrating group?