Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

Chemistry (Organic) > Aromatic > Flashcards

Aromatic Flashcards

1
Q

Describe the bonding in benzene

A

Each carbon is covalently bonded to 2C’s and 1 H
Each C atom has 1 unbonded e- in its p orbital
P orbitals overlap to give a ring of delocalisation above and below the plane
This ring gives it stability

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

What gives benzene stability

A

Each C atom has 1 unbonded e- in its p orbital
P orbitals overlap to give a ring of delocalisation above and below the plane
This ring gives it stability

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

Where does the ring of delocalisation lie

A

Above AND below the plane

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

Describe the shape of benzene

A

Trigonal planar arrangement around each carbon giving a bond angle of 120 degrees
Therefore benzene is planar

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

Describe the bond length in benzene

A

Intermediate between single and double bond

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

Draw the both structures of benzene

A
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

Write the equation for the hydrogenation of cyclohexene stating the enthalpy change for the reaction

A
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

Write the equation for the hydrogenation of cyclohexa-1,4-diene and cyclohexan-1,3-diene, for both isomers, stating the enthalpy change for each reaction

A
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

Explain why the enthalpy change for the hydrogenation of cyclohexa-1,4-diene and cyclohexan-1,3-diene are different

A

C=C bonds in 1,4 diene are too far apart to allow overlap of p orbitals, so there is no additional delocalisation and no additional stability
In 1,3 diene, a section of the molecule is alternating, double single double bond. This allows for the overlap of p orbitals giving delocalisation which gives the 1,3 isomer extra stability and more energy is required to break the structure and so is less exothermic

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

Write an equation for the THEORETICAL hydrogenation of benzene, stating the expected enthalpy change

A
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

Write an equation for the ACTUAL hydrogenation of benzene, stating the expected enthalpy change

A
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

Explain why the theoretical value for the hydrogenation of benzene differs from the actual value

A

Kekule/theoretical structure assumes there is no delocalisation of p electrons/no delocalised ring which confers stability to the molecule

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

How much more stable is the actual structure of benzene compared to kekules structure

A

Benzene is 152KJmol-1 more stable (360 - 208)
Hydrogenation of benzene is 152KJmol-1 less exothermic than the theoretical molecule

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

What are the 2 electrophiles which can react with benzene in electrophilic substitution

A

Nitronium ion (NO2+)
Acylium ion (RCO+)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

What is the name of the mechanism for the nitration of benzene

A

Electrophilic substitution

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

What is the name of the mechanism for the acylation of benzene

A

Electrophilic substitution

17
Q

Name and outline the mechanism for the nitration of benzene

A

Electrophilic substitution

18
Q

Name and outline the mechanism for the acylation of benzene

A

Electrophilic substitution

19
Q

What are the 3 stages in either nitration or acylation of benzene

A

1- Generation of electrophile
2- Mechanism
3 - Regeneration of catalyst

20
Q

What catalyst is used in the acylation of benzene?

A

AlCl3

21
Q

Write an equation for the generation of the acylium ion

A
22
Q

Write an equation for the regeneration of the catalyst used in the acylation of benzene

A
23
Q

What is the overall equation for the acylation of benzene

A

C6H6 + RCOCl —> C6H5COR + HCl

24
Q

What is the reagent, catalyst and conditions required for the acylation of benzene

A

Reagent: RCOCl
Catalyst: AlCl3
Conditions: Anhydrous conditions, reflux, 50 degrees C

25
Q

What catalyst is used in the nitration of benzene?

A

H2SO4

26
Q

Write an equation for the generation of the nitronium ion in the nitration of benzene

A
27
Q

Write an equation for the regeneration of the catalyst used in the nitration of benzene

A
28
Q

What is the overall equation for the nitration of benzene

A

C6H6 + HNO3 —> C6H5NO2 + H2O

29
Q

What is the reagent, catalyst and conditions required for the nitration of benzene

A

Reagent: Concentrated HNO3
Catalyst: Concentrated H2SO4
Conditions: Room temperature and pressure

30
Q

What is the name of the molecule produced from the nitration of benzene

A

Nitrobenzene

31
Q

What is the general name of the molecule produced from the acylation of benzene

A

Phenylketone

32
Q

What is the theoretical benzene molecule called

A

cyclohexa-1,3,5-triene

33
Q

Why does benzene undergo substitution and not addition

A

Benzene is stable, therefore they do not undergo electrophilic addition reactions as it would disrupt the stable ring of electrons

34
Q

Why is the acylation of benzene important

A

Benzene is widely used, yet due to its stability it is difficult to react, acylation can help to solve this by weakening the structure of benzene making it easier to modify into useful products

35
Q

Why is the nitration of benzene useful

A

Allows us to
Make dyes for clothing by reducing nitrobenzenes to aromatic amines
Making explosives such as TNT

Chemistry (Organic) (10 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2025 Bold Learning Solutions. Terms and Conditions