Chapter 4 - Aromatic Compounds

Question 1

Molecular Structure of Benzene

Answer 1

C6H6

Question 2

Benzene mainly reacts by what reaction?

Answer 2

Substitution

Question 3

True or False:

Benzene is planar

Answer 3

True

Question 4

Symbol for benzene where

• electrons are distributed evenly around the ring
• perhaps the more accurate of the two

Answer 4

Delocalized pi cloud

Question 5

True or False

Resonance hybrid is always more stable than any of its contributing structures.

Answer 5

True

Question 6

Chemical reactivity of Benzene

Answer 6

Electrophilic substitution

Question 7

involve substitution of other atoms or groups for a ring hydrogen on the aromatic unit

Answer 7

Electrophilic Aromatic Substitution

Question 8

Carbon atom undergoing electrophilic aromatic substitution becomes what?

Answer 8

Sp3-hybridized

Question 9

It is similar to an allylic carbocation but the positive charge is delocalized over three carbon atoms instead of only two

Answer 9

Benzenonium ion

Question 10

It is the completed by loss of a proton from the sp3 carbon atom, the same atom to which the electrophile became attached.

Answer 10

Substitution

Question 11

What is the catalyst used in halogenation?

Answer 11

Iron halide

Question 12

The electrophile in nitration

Answer 12

Nitronium ion

Question 13

It protonates the nitric acid, which then loses water to generate the nitronium ion (NO2+), which contains a positively charged nitrogen atom

Answer 13

Sulfuric acid catalyst

Question 14

A carbocation, which can be formed either by removing a halide ion from an alkyl halide with a Lewis acid catalyst example

Answer 14

Electrophile

Question 15

Electrophile of acylation

Answer 15

Acyl cation

Question 16

It provides a useful general route to aromatic ketones.

Answer 16

Friedel-Crafts reaction - acylation

Question 17

What groups are more electron donating than hydrogen? (2)

Answer 17

Hydroxyl and methyl groups

Question 18

What groups are more electron withdrawing than hydrogen? (2)

Answer 18

Chloro and nitro groups

Question 19

• places the positive charge on the hydroxyl-bearing carbon
• Shift of an unshared electron pair from the oxygen to the positive carbon allows the positive charge to be delocalized even further, onto the oxygen

Answer 19

Ortho, para-directing groups

Question 20

• has two adjacent positive charges
• a highly undesirable arrangement because like charges repel each other

Answer 20

Meta-directing groups

Question 21

Activating or Deactivating?

if the rate of electrophilic aromatic substitution is faster for the substituted benzene than for unsubstituted benzene.

Answer 21

Activating

Question 22

Activating or Deactivating?

if the rate of reaction is slower than for benzene

Answer 22

Deactivating

Question 23

True or False:

If we brominate first and then nitrate, we will get a mixture of meta isomers.

Answer 23

False
(ortho and para isomers)

Question 24

Is bromine atom ortho,para directing or meta directing?

Answer 24

Ortho, para directing

Question 25

Is nitro group ortho, para directing or meta directing?

Answer 25

Meta directing

Question 26

The unusual stability of certain fully conjugated cyclic systems

Answer 26

Aromaticity

Question 27

Contain at least 2 benzene rings; each ring shares two carbon atoms with at least one other ring

Answer 27

Fused polycyclic hydrocarbon