Aromatic Hydrorbons

Question 1

It is the simplest member of the aromatic hydrocarbons/arenes, with the molecular formula:

Answer 1

Benzene, C6H6

Question 2

Structure of Benzene:

Answer 2

• Alternating single & double bonds
• It is formed in a ring of 6 Carbons
• There is 1 Hydrogen atom attached to each Carbon

Question 3

All six carbon-carbon bonds of benzene are the _____ length, intermediate between _______ single and double bonds.

Answer 3

Same; sp^2-sp^2

Question 4

A convenient way to represent the two Kekulé structures as resonance forms of benzene is by:

Answer 4

Inscribing a circle inside a hexagon

Question 5

How is a Substituted Derivative of Benzene formed?

Answer 5

It is formed when a Benzene ring has one of its hydrogens replaced by some other group

C6H5 + other compound

Question 6

Types of Substituted Derivatives of Benzene

Answer 6

1. Monosubstituted benzene ring - one substituent to ring
2. Disubstituted benzene ring - two substituents to ring
3. Multi-substituted benzene ring - three or more substituents to ring

Question 7

As a Monosubstitute, C6H6 as the parent can be prefixed by:

Answer 7

• Alkyl groups: methyl, ethyl, propyl, butyl, etc.
• Halogens: Br, Cl, I, F
• Nitro groups: NO2

Question 8

Monosubstituted benzene can also be considered the substituent instead of a parents when it is attached to an:

Answer 8

• Alkane chain with a functional group
• Alkane chain of seven or more Carbon atoms

Question 9

The name for benzene as a substituent is:

Answer 9

Phenyl

Question 10

Disubstituted benzene rings are named either with:

Answer 10

• Position numbers
• Prefixed by:

1. Ortho (o): substituents are 1, 2
2. Meta (m): substituents are **1,3 **
3. Para (p): substituents are 1,4

Question 11

These are the dimethyl (2CH3) derivatives of benzene:

Answer 11

Xylene

Question 12

There are three xylene isomers, namely:

Answer 12

Ortho-, meta-, para- substituted derivatives

Question 13

In naming multisubstitured benzene rings, the substituents are numbered on the ring beginning with:

Answer 13

The group that forms the basis, or is considered the parent

Question 14

Preparing Benzene through Sodalime Method:

Answer 14

C6H5COONa + NaOH —>[CaO] C6H6 + Na2CO3

The H from NaOH is added to the arene, making it C6H6

Question 15

Preparing Benzene through Heating Phenol with Zinc Dust:

Answer 15

C6H5OH + Zn —> C6H6 + ZnO

Reduction occurs, because the arene-phenol loses its O atom to Zn, and the remaining H atom moves to C6H5

Question 16

Preparing Benzene through Grignard Reaction:

Answer 16

C6H5Br + Mg —> [dry ether] C6H5MgBr aka Grignard Reagent

C6H5MgBr + H2O —> C6H6 + MgOHBr

Question 17

Preparing Benzene through Polymerization of 3 moles of acetylene:

Answer 17

3 HC≈CH —> [Fe / 240C] C6H6

Question 18

• The special stability of benzene and its derivatives
• Benzenes experience low chemical reactivity because of this

Answer 18

Aromaticity

Question 19

Combustion of arenes:

Answer 19

2 C6H6 + 15 O2 —> CO2 + 6 H2O

Exposure of arene to oxygen gas leads to formulation of carbon dioxide and water

Question 20

In halogenating arenes, C6H6 reacts with 3 Cl2 or 3 Br2 with ______ catalyst to form:

Answer 20

UV / heat catalyst

C6H6 + 3 X2 (six X atoms) —> Benzene hexachloride or Benzene hexabromide

Compound is not aromatic anymore

Question 21

On the other hand, when catalyzed by halogen carriers, benzene reacts with halogens Br2 or Cl2 to form:

Answer 21

Halobenzene or C6H6-X and HX gas byproduct

C6H6 + X2 —>[halogen carrier] C6H5-X + HX

Question 22

Halogen carriers can either be:

Answer 22

• AlX3
• Fe
• FeX3
• L2

Question 23

In Nitration of benzene, a mix of _____ and _____ called nitrating acid convert benzene into ______ at the temperature of 30-40 Celsius

Answer 23

H2OSO3 or Sulfuric acid + HNO3 or Nitric acid

converted into Nitrobenzene

Question 24

Why is H2OSO3 added to HNO3 in Nitration?

Answer 24

H2OSO3 is a dehydrating agent, therefore takes away the H & 1 O from HNO3 and connects substitued benzene H atom to them to form H2O

Question 25

In Sulfonation, when sulfuric acid (H2OSO3) is heated, ____ is formed and goes in between a benzene’s C and H atom

Answer 25

SO3 or Sulfur trioxide

C6H6 + H2OSO3 –>[heat]

Question 26

In Friedel-Crafts Alkylation, a benzene reacts with _____ with catalyst _____ to form carbocation

Answer 26

Alkyl halide; AlCl3 or Aluminum Chloride

Question 27

Benzene is a colorless liquid which is insoluble in _____, but soluble in _____

Answer 27

Water

Organic compounds

Question 28

Increasing activation (ortho, para directives) order:

Answer 28

1. NH2 / Aniline
2. OH / Phenol
3. OR / Anisole
4. NHCOR / Acetanilide
5. C6H5 / Aryl
6. Alkyl
7. Cl, Br / Halogen

Question 29

In the Oxidation of benzene homologues leads to formation of _____

Answer 29

Arenecarboxyclic acids

*Benzene substituents when oxidized are replaced by COOH

Question 30

These are aromatic compounds that contain 2 or more aromatic rings

Answer 30

Policyclic aromatic compounds

Question 31

How are policyclic aromatic compounds fused together?

Answer 31

By sharing a common carbon-to-carbon bond

Question 32

Type of aromatic compounds that are cyclic molecules that contain at least one other atom other than C in the ring structure.

Answer 32

Heterocyclic aromatic compounds