Question 1

Which of the following statements best describes the molecular orbitals of 1,3-butadiene?

Accepted Answer

There are 4 molecular orbitals: 2 bonding and 2 antibonding.

Question 2

Which of the following best explains why the HOMO-LUMO gap in 1,3-butadiene is smaller than in ethylene?

Accepted Answer

Because 1,3-butadiene has more conjugated double bonds, which increases delocalization and decreases the energy gap.

Question 3

Which of the following is true regarding the nodal planes in the molecular orbitals of conjugated systems?

Accepted Answer

The number of nodal planes increases with increasing energy.

Question 4

In the resonance structures of the allyl cation, which atom carries the positive charge in the most stable resonance form?

Accepted Answer

The central carbon atom.

Question 5

Which of the following best describes the product of a 1,4-conjugate addition to an α,β-unsaturated ketone?

Accepted Answer

The nucleophile adds to the β-carbon.

Question 6

Which statement about the NBS (N-bromosuccinimide) reaction is correct?

Accepted Answer

NBS selectively brominates the benzylic position of an alkylbenzene.

Question 7

Which of the following is a key feature of aromatic compounds according to Hückel's rule?

Accepted Answer

They must have $$(4n+2)$$ π electrons, where $$n is an $$integer.

Question 8

Which substituent is considered an ortho/para director in electrophilic aromatic substitution?

Accepted Answer

-OH

Question 9

What is the major product when benzene is treated with Br$$_2$$ and FeBr$$_3$$?

Accepted Answer

Bromobenzene

Question 10

Which of the following best describes the effect of an electron-withdrawing group (EWG) on the reactivity of a diene in a Diels-Alder reaction?

Accepted Answer

It decreases the reactivity of the diene.

Question 11

Which of the following is true about the resonance stabilization of allylic carbocations?

Accepted Answer

Allylic carbocations are stabilized by delocalization of the positive charge over multiple carbons.

Question 12

Which of the following is a correct statement about the stereochemistry of the Diels-Alder reaction?

Accepted Answer

The stereochemistry of the diene and dienophile is preserved in the product.

Question 13

Which of the following is the correct order of stability for carbocations?

Accepted Answer

Primary \u003c Secondary \u003c Tertiary

Question 14

Which of the following is a limitation of Friedel-Crafts alkylation?

Accepted Answer

Carbocation rearrangement can occur, leading to unexpected products.

Question 15

Which of the following is true about anti-aromatic compounds?

Accepted Answer

They have 4n π electrons and are destabilized by delocalization.

Question 16

Which of the following is the correct product of the oxidation of a benzylic methyl group with KMnO$$_4$$?

Accepted Answer

Benzoic acid

Question 17

Which of the following is a correct statement about the effect of substituents on the rate of electrophilic aromatic substitution?

Accepted Answer

Electron-donating groups increase the rate.

Question 18

Which of the following is the correct mechanism for the nitration of benzene?

Accepted Answer

Benzene reacts with HNO$$_3$$ and H$$_2SO$_4 to $$form nitrobenzene.

Question 19

Which of the following statements about the stability of conjugated dienes is correct?

Accepted Answer

Conjugated dienes are more stable than isolated dienes due to delocalization of electrons.

Organic Chemistry II: Structure, Stability, Molecular Orbitals, and Aromatic Compounds

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