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Flashcards in Aromatic Chemistry Deck (44)
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1

Molecular formula of benzene

C6H6

2

What did Kekule dream of?

Benzene’s structure of alternating double and single bonds

3

What would be the IUPAC name for Kekule’s structure?

Cyclohexatriene

4

What are the problems with Kekule’s structure?

1. Benzene does not decolourise bromine water (if it was unsaturated it should undergo Electrophilic addition)

2. Benzene bonds are all the same length and intermediate between Normal C-C bonds and C=C bonds

5

List the different C bonds in order of length

C-C>C-C(benzene) > C=C

6

How are the electrons arranged in benzene

In a delocalised ring

7

How to tell the difference between cyclohexane and benzene

Benzene must have a delocalised ring

8

Describe bonding in Benzene

Each C forms 3 bonds in trigonal planar structure
Forth valence (outer e-) in 2p overlaps with 4th e-‘s of adjacent C’s resulting in a ring

9

What is the thermochemical evidence for delocalisation in Benzene

Expected 🔺H is -360 kJmol-1
Actual 🔺H is -208 kJmol-1
Which is 152 kJmol-1 less exothermic

Therefore benzene is more stable than Kekule’s structure due to delocalised ring of e-

10

What reaction is used to provide evidence for Kekule’s structure being incorrect?

🔺H of hydrogenation of benzene

11

How to name aromatic compounds if the benzene ring has a functional group attached directly to it

Use benzene suffix

12

How to name a compound with an R group or ester link attached to the benzene ring

Use the prefix “phenyl”

13

What is the name used for C chains not including benzene

Aliphatic

14

Define aromatic

Contains a benzene ring

15

Define Electrophile

E- pair acceptor

16

Define nitronium ion

NO2+

17

What is an acylium ion

O
||
R-C+

18

Name of +NO2

Nitronium ion

19

3 steps for electrophilic substitution

1) generation of electrophile
2) electrophilic substitution
3) regeneration of catalyst

20

Why is it called electrophilic substitution

H+ substituted for electrophile

21

What are the conditions and reactants for electrophilic substitution for the notation of benzene

What is produced

Concentrated HNO3 and Concentrated H2SO4
50 degrees C

Nitrobenzene

22

Equation for nitration of benzene

Conc.
H2SO4
Benzene + HNO3 ————-> water + nitrobenzene

23

Give 2 steps to produce electrophile for nitration of benzene

H2SO4 protonates HNO3

Protonated nitric acid breaks down to form nitronium ion and water

24

Give two equations for the generation of electrophile in nitration of benzene

H2SO4 + HNO3—-> H2NO3+ + HSO4-

H2NO3+ ——> NO2+ + H2O

25

Give overall equation for generation of electrophile in nitration of benzene

H2SO4 + HNO3 ——> HSO4- + NO2+ + H2O

26

How to draw intermediate in electrophilic addition

Horseshoe must be centred around where electrophile is attacking

27

Equation for Regeneration of electrophile in nitration of benzene

HSO4- + H+ —-> H2SO4

28

What is nitrobenzene used for ?

Preparation of azo dyes

29

Reactants and conditions for reduction of nitrobenzene

What is produced

Sn catalyst and concentrated HCl
Reflux

Reflux

Amino benzene

30

When Nitrobenzene becomes amino benzene, what is the catalyst and what does it act as?

How to show this in an equation?

Sn

Reducing agent

[H]