Q: Which of the following molecules is aromatic according to Huckel’s rule?

A planar, cyclic molecule with 6 $$\\pi$$ electrons

Question 1

Which of the following substituents on a benzene ring is meta-directing towards electrophiles in electrophilic aromatic substitution reactions?

Accepted Answer

A nitro group ($$NO_2)$$

Question 2

Rank the following compounds in order of increasing reactivity towards electrophilic aromatic substitution: benzene, nitrobenzene, toluene, and chlorobenzene.

Accepted Answer

$$NO_2-$$benzene \u003c chlorobenzene \u003c benzene \u003c toluene

Question 3

Which of the following molecules is aromatic according to Huckel’s rule?

Accepted Answer

A planar, cyclic molecule with 6 $$\pi$$ electrons

Question 4

Which of the following best describes the first step in the Friedel-Crafts alkylation mechanism?

Accepted Answer

Formation of a carbocation from the alkyl halide and Lewis acid

Question 5

A side-product in Friedel-Crafts alkylation can result from rearrangement of the carbocation intermediate. Which of the following is a likely byproduct?

Accepted Answer

A mono-alkylated benzene with a rearranged alkyl group

Question 6

A compound absorbs at a longer wavelength in UV-Vis spectroscopy after a reaction. What structural change most likely occurred?

Accepted Answer

Increased conjugation in the product

Question 7

What is the expected major product when excess $$Br_2 is $$added to anisole ($$methoxybenzene$$)?

Accepted Answer

2,4,6-tribromoanisole

Question 8

Which of the following is the more stable tautomer of butanal?

Accepted Answer

The aldehyde form ($$CH_3CH_2CH_2CHO)$$

Question 9

Given the molecular formula $$C_{11}H$$_{14}$$O$$ and the $$^1H$$ NMR data: $$\delta 9.9 (s$$, 1H), $$\delta 7.8 (d$$, 2H), $$\delta 7.1 (d$$, 2H), $$\delta 2.4 (d$$, 2H), $$\delta 1.8 (m$$, 1H), $$\delta 0.9$ (d, 6H), what is the most likely structure?

Accepted Answer

p-isopropylbenzaldehyde

Question 10

Which of the following statements about acetal protecting groups is correct?

Accepted Answer

Acetals are cleaved by aqueous acid to regenerate the carbonyl compound

Question 11

Which intermediate is formed during the acid-catalyzed cleavage of an acetal?

Accepted Answer

An oxonium ion ($$R_2C(OH)^+)$$

Question 12

In the synthesis of acetaminophen, which functional group transformation occurs in the final step?

Accepted Answer

Amide formation from an amine and an acyl group

Question 13

Which of the following best explains why chlorobenzene undergoes electrophilic aromatic substitution more slowly than benzene?

Accepted Answer

The chlorine atom is electron-withdrawing by induction

Question 14

Which of the following is a common side reaction in Friedel-Crafts alkylation when using a primary alkyl halide?

Accepted Answer

Carbocation rearrangement leading to a more stable alkyl group

Question 15

Which of the following statements about activating groups in electrophilic aromatic substitution is correct?

Accepted Answer

Activating groups are generally ortho/para-directing

Question 16

Which of the following best describes the effect of conjugation on the UV-Vis absorption of a molecule?

Accepted Answer

Conjugation increases the wavelength of maximum absorption ($$\lambda_{max})$$

Question 17

Which of the following is NOT a criterion for aromaticity according to Huckel’s rule?

Accepted Answer

The molecule must have an even number of $$\pi$$ electrons

Question 18

Which of the following best explains why acetals are used as protecting groups for carbonyl compounds?

Accepted Answer

Acetals are stable to base and nucleophiles but cleaved by acid

Question 19

Which of the following is the correct order of reactivity towards electrophilic aromatic substitution for the following substituents: $$NO_2$$, $$Cl$$, $$H$$, $$CH_3$$?

Accepted Answer

$$NO_2$$ \u003c Cl \u003c H \u003c $$CH_3$$

Aromaticity and Huckel’s Rule: Classifying Molecules

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