$$\Delta H_{pred} = -360\ \text{kJ/mol}$$

Question 1

Which of the following is NOT a requirement for a compound to be considered aromatic according to Hückel’s Rule?

Accepted Answer

The compound must have 2 + 4n electrons in its pi system.

Question 2

Which molecular orbital model best explains the stability of benzene compared to cyclohexatriene?

Accepted Answer

Molecular orbital (LCMO) model

Question 3

What is the predicted heat of hydrogenation for benzene if it were simply three isolated double bonds?

Accepted Answer

$$\Delta H_{pred} = -360\ 	ext{kJ/mol}$$

Question 4

Which of the following compounds is aromatic according to Hückel’s Rule?

Accepted Answer

[6]annulene

Question 5

Why does pyrrole have a much lower pKa than pyridine?

Accepted Answer

Pyrrole’s nitrogen lone pair is involved in aromaticity, making it less basic.

Question 6

Which of the following statements about benzylic halogenation is TRUE?

Accepted Answer

Benzylic halides react well by SN2 and SN1 mechanisms.

Question 7

Which of the following ions is aromatic and unusually stable?

Accepted Answer

Cyclopentadienyl anion

Question 8

What is the effect of the Birch reduction on benzene?

Accepted Answer

It selectively reduces benzene to a non-aromatic 1,4-cyclohexadiene.

Question 9

Which of the following is a characteristic reaction of aromatic compounds?

Accepted Answer

Reactions that preserve the aromatic ring

Question 10

Which of the following best describes the molecular orbitals in benzene?

Accepted Answer

Six molecular orbitals: three bonding and three antibonding

Question 11

Which of the following is NOT a property of aromatic compounds?

Accepted Answer

They react like typical alkenes in addition reactions.

Question 12

Which of the following heteroatoms can contribute two electrons to an aromatic system?

Accepted Answer

Oxygen in furan

Question 13

What is the relationship between the prefixes ortho-, meta-, and para- and the positions of substituents on a benzene ring?

Accepted Answer

Ortho- refers to 1,2-, meta- to 1,3-, and para- to 1,4- positions.

Question 14

Which of the following is a polycyclic aromatic compound (PAC) found in chimney soot and cigarette smoke and is associated with cancer?

Accepted Answer

Benzo[a]pyrene

Question 15

Which of the following statements about fused aromatic systems is TRUE?

Accepted Answer

Phenanthrene is overall aromatic, but one bond is more reactive.

Question 16

Which of the following is the correct formula for Hückel’s Rule?

Accepted Answer

$$4n + 2$$ electrons

Question 17

Which of the following is NOT a typical outcome of benzylic oxidation with KMnO4?

Accepted Answer

Oxidation of a benzylic hydrogen to a hydroxyl group

Question 18

Which of the following statements about the molecular orbital diagram for 1,3-butadiene is TRUE?

Accepted Answer

There are four molecular orbitals formed from four p orbitals.

Question 19

Which of the following is a consequence of the aromatic ring current detected by NMR?

Accepted Answer

Aromatic protons are deshielded and appear downfield.

Question 20

Which of the following statements about the chemistry of ferrocene is TRUE?

Accepted Answer

Ferrocene contains two aromatic cyclopentadienyl anions coordinated to Fe$$^{2+}.$$

Aromaticity: Structure, Stability, and Reactivity of Aromatic Compounds

Study Guide - Practice Questions