15

Question 1

What are aromatic compounds?

Answer 1

Group of compounds that contain six-membered benzene-like rings with three alternate double bonds.

Question 2

What are the two main sources of simple aromatic hydrocarbons?

Answer 2

• Coal
• Petroleum

Question 3

How is coal tar formed?

Answer 3

Thermal breakdown of coal occurs when it is heated to 1000 °C in the absence of air.

Question 4

What does fractional distillation of coal tar yield?

Answer 4

• Benzene
• Toluene
• Xylene (dimethylbenzene)
• Naphthalene
• Other aromatic compounds

Question 5

What is the primary composition of petroleum?

Answer 5

Petroleum consists largely of alkanes and contains few aromatic compounds.

Question 6

What is the common name for methylbenzene?

Answer 6

Toluene

Question 7

What is the common name for hydroxybenzene?

Answer 7

Phenol

Question 8

What is the common name for aminobenzene?

Answer 8

Aniline

Question 9

What are alkyl-substituted benzenes sometimes referred to as?

Answer 9

Arenes

Question 10

How are disubstituted benzenes named?

Answer 10

Using the prefixes ortho (o), meta (m), or para (p).

Question 11

What is the bond length of carbon-carbon bonds in benzene?

Answer 11

139 pm

Question 12

What is the bond angle in benzene?

Answer 12

120°

Question 13

What type of hybridization do all carbon atoms in benzene exhibit?

Answer 13

sp2-hybridized

Question 14

What is the resonance structure of benzene?

Answer 14

Benzene is a hybrid of two equivalent forms.

Question 15

What is the heat of hydrogenation of benzene compared to typical alkenes?

Answer 15

150 kJ/mol less negative than expected for a conjugated cyclic triene.

Question 16

What is the Hückel 4n + 2 rule?

Answer 16

A molecule is aromatic if it has a planar, monocyclic system of conjugation with p orbitals on each ring atom and contains (4n + 2) π electrons.

Question 17

What happens to molecules with 4n π electrons?

Answer 17

They are antiaromatic and destabilized.

Question 18

Is cyclobutadiene aromatic or antiaromatic?

Answer 18

Antiaromatic

Question 19

What is the structure of cyclooctatetraene?

Answer 19

Tub-shaped and not planar.

Question 20

What defines a heterocyclic compound?

Answer 20

A cyclic compound that contains atoms of two or more elements in its ring.

Question 21

What is the total number of π electrons in pyridine?

Answer 21

Six π electrons

Question 22

How many π electrons does pyrrole have?

Answer 22

Six π electrons

Question 23

What is the significance of the nitrogen lone pair in pyrrole?

Answer 23

It contributes two electrons to the aromatic π system.

Question 24

What does the term ‘aromatic heterocycles’ refer to?

Answer 24

Cyclic compounds that contain heteroatoms in the ring and meet the criteria for aromaticity.

Question 25

What is the common name for the cyclopentadienyl anion?

Answer 25

Aromatic despite being an ion with six π electrons.

Question 26

What is the difference between aromatic and antiaromatic compounds?

Answer 26

Aromatic compounds have (4n + 2) π electrons, while antiaromatic compounds have 4n π electrons.

Question 27

What happens to the stability of a molecule with an incomplete π electron filling?

Answer 27

It becomes unstable.

Question 28

What type of hybridization do the carbons in pyrrole exhibit?

Answer 28

sp2-hybridized

Question 29

How many π electrons does each carbon contribute in pyrrole?

Answer 29

one π electron

Question 30

How many π electrons does the nitrogen atom contribute in pyrrole?

Answer 30

two from its lone pair

Question 31

What is the structure of imidazole?

Answer 31

Five-membered ring with two nitrogen atoms

Question 32

In imidazole, how many π electrons does N#3 contribute?

Answer 32

one electron

Question 33

In imidazole, how many π electrons does N#1 contribute?

Answer 33

two from its lone pair

Question 34

What are the three heterocyclic amine bases found in nucleic acids derived from pyrimidine?

Answer 34

* cytosine * thymine * uracil

Question 35

What is a notable amino acid that contains an aromatic imidazole ring?

Answer 35

histidine

Question 36

What does the Hückel rule apply to?

Answer 36

Monocyclic compounds

Question 37

Name a few well-known polycyclic aromatic hydrocarbons.

Answer 37

* naphthalene * anthracene * benzo[a]pyrene * coronene

Question 38

What is benzo[a]pyrene known for?

Answer 38

It is a cancer-causing substance found in tobacco smoke

Question 39

How many resonance forms can naphthalene be represented by?

Answer 39

Three

Question 40

What is the aromatic stabilization energy of naphthalene?

Answer 40

Approximately 250 kJ/mol (60 kcal/mol)

Question 41

What type of products do naphthalene and electrophiles like Br2 form?

Answer 41

Substitution products

Question 42

What does naphthalene's aromaticity depend on?

Answer 42

Cyclic, conjugated π electron system

Question 43

What are some heterocyclic analogs of naphthalene?

Answer 43

* quinoline * isoquinoline * indole * purine

Question 44

What type of nitrogen do quinoline and isoquinoline contain?

Answer 44

Pyridine-like nitrogen

Question 45

What type of nitrogen do indole and purine contain?

Answer 45

Pyrrole-like nitrogen

Question 46

Which amino acid contains an indole ring?

Answer 46

tryptophan

Question 47

What type of ring does the antimalarial drug quinine contain?

Answer 47

quinoline ring

Question 48

Which two bases in nucleic acids are based on purine?

Answer 48

* adenine * guanine