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Organic Chemistry > Aromatic Chemistry > Flashcards

Aromatic Chemistry Flashcards

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1
Q

Molecular formula of benzene

A

C6H6

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2
Q

What did Kekule dream of?

A

Benzene’s structure of alternating double and single bonds

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3
Q

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

A

Cyclohexatriene

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4
Q

What are the problems with Kekule’s structure?

A
  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
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5
Q

List the different C bonds in order of length

A

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

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6
Q

How are the electrons arranged in benzene

A

In a delocalised ring

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7
Q

How to tell the difference between cyclohexane and benzene

A

Benzene must have a delocalised ring

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8
Q

Describe bonding in Benzene

A 
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
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9
Q

What is the thermochemical evidence for delocalisation in Benzene

A

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-

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10
Q

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

A

🔺H of hydrogenation of benzene

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11
Q

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

A

Use benzene suffix

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12
Q

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

A

Use the prefix “phenyl”

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13
Q

What is the name used for C chains not including benzene

A

Aliphatic

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14
Q

Define aromatic

A

Contains a benzene ring

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15
Q

Define Electrophile

A

E- pair acceptor

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16
Q

Define nitronium ion

A

NO2+

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17
Q

What is an acylium ion

A

O
||
R-C+

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18
Q

Name of +NO2

A

Nitronium ion

19
Q

3 steps for electrophilic substitution

A

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

20
Q

Why is it called electrophilic substitution

A

H+ substituted for electrophile

21
Q

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

What is produced

A

Concentrated HNO3 and Concentrated H2SO4
50 degrees C

Nitrobenzene

22
Q

Equation for nitration of benzene

A

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

23
Q

Give 2 steps to produce electrophile for nitration of benzene

A

H2SO4 protonates HNO3

Protonated nitric acid breaks down to form nitronium ion and water

24
Q

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

A

H2SO4 + HNO3—-> H2NO3+ + HSO4-

H2NO3+ ——> NO2+ + H2O

25
Q

Give overall equation for generation of electrophile in nitration of benzene

A

H2SO4 + HNO3 ——> HSO4- + NO2+ + H2O

26
Q

How to draw intermediate in electrophilic addition

A

Horseshoe must be centred around where electrophile is attacking

27
Q

Equation for Regeneration of electrophile in nitration of benzene

A

HSO4- + H+ —-> H2SO4

28
Q

What is nitrobenzene used for ?

A

Preparation of azo dyes

29
Q

Reactants and conditions for reduction of nitrobenzene

What is produced

A

Sn catalyst and concentrated HCl
Reflux

Reflux

Amino benzene

30
Q

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

How to show this in an equation?

A

Sn

Reducing agent

[H]

31
Q

Give the general and IUPAC name for TNT

A

Trinitrotoluene

Or

2-methyl-1,3,5- trinitrobenzene

32
Q

What are nitrated arenes used for?

A

Making TNT

33
Q

How is trinitrotoluene formed

A

Methyl benzene makes ring more susceptible to electrophilic attack and so 3 NO2+ ions are added in electrophilic substitution

34
Q

What kind of mechanism is a Friedel-Craft Acylation Reaction?

A

Electrophilic substitution

35
Q

How is a phenyl ketone formed?

A

Benzene reacts with an acyl chlorides in the presence of AlCl3

36
Q

Give structure of an acyl chloride

A

O
||
R-C-Cl

37
Q

Give overall equation for formation of phenyl ketone

A

AlCl3

Benzene + RCOCl ———> phenyl ketone + HCl

38
Q

Equation for generation of electrophile for an acylation reaction with benzene

A

RCOCl + AlCl3 ——> RCO+ + AlCl4-

39
Q

Structure of acylium ion

A

O
||
R-C+

40
Q

Equation for regeneration of catalyst

A

AlCl4- + H+ —-> AlCl3 + HCl

41
Q

What can be used to form a phenyl ketone?

A

Benzene + acyl chloride or acid anhydride

42
Q

Simple laboratory process to show an aromatic product is pure

A

Measure melting point using melting point apparatus

A shape melting point indicates the product is pure

43
Q

Bond angle of benzene and cyclohexane

A

Benzene: 120
Cyclohexane: 109.5

44
Q

Why is benzoic acid Insoluble

A

Despite polarity of COOH

Benzene ring is non polar

Organic Chemistry (12 decks)

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