Ocr Chemistry Unit 1: Module 1 - Rings, Acids And Amines

Front 1

Benzene

What are arenes?

Back 1

Aromatic hydrocarbons containing one or more benzene ring

Front 2

Benzene

Describe the properties of Benzene

Back 2

- Colourless liquid

- C6H6

- Has a sweet odour

- Is flammable

Front 3

Benzene

What was Kekulé's original model for Benzene?

Back 3

Alternating double bonds in a ring of six carbons.

Front 4

Benzene

Why was this model not accepted?

Back 4

* If C=C double bonds were present, benzene would act as an alkene and decolourise bromine water, BUT it does not react at all - the approaching bromine molecule is not attracted to the C=C bond.

* All the C-C bonds were found to have the same length

* All internal bond angles were found to be 120°

* When the enthalpy of hydrogenation of a C=C bond is measured it = -120kJmol-1, so benzene should have an enthalpy of hydrogenation of 3x(-120kJmol-1) but it does not.

Front 5

Benzene

Describe the real model for the structure of benzene

Back 5

6 carbon atoms arranged in a planar hexagonal ring

Bond angles are trigonal planar - 120° around each carbon

The electrons in one p-orbital of one carbon atom overlaps with electrons in other p-orbitals. This overlap produces a system of pi-bonds, in which electrons are delocalised in a ring of electron density

Front 6

Benzene

Why is Benzene less reactive than alkenes?

Back 6

(It does not react with bromine water to decolourise it or react with strong acids such as HCl or react with halogens such as Cl, Br or I.)

Benzene is less reactive because

a) the delocalised system of benzene of benzene is very stable

b) to take part in addition reactions an electron from the already stable ring would have to bond to a different atom- forming something that is less stable. This is not energetically favourable.

c) It would disrupt the delocalisation of the ring structure.

Front 7

Benzene

What kind of reactions does Benzene take part in?

(Be specific pls)

Back 7

Substitution - one of the hydrogens in the benzene ring is replaced by another atom/group of atoms.

This does not disrupt the stability of the delocalisation of the ring.

Specifically ;) the region of high electron density above and below the carbon plane attracts electrophiles - and so takes part in electrophilic substitution.

Front 8

Benzene

Draw the nitration of benzene and the conditions required

Back 8

Front 9

Benzene

What is the method for the nitration of benzene?

Back 9

1) Prepare the nitrating mixture in a round-bottom flask

2) Mix concentrated HNO3 and concentrated H2SO4 carefully while cooling in a beaker of cold water

3) Add benzene carefully to the nitrating mixture - keep below 50°C

4) Once all the benzene is added, fit a reflux condenser and heat to 50°C in a water bath

Front 10

Benzene

What can happen if the reaction of nitration of benzene gets hotter than 50°C?

Back 10

More than one nitro group is substituted

Front 11

Benzene

Outline the nitration of methylbenzene/Toluene

(HINT- it's dynamite)

Back 11

Methylbenzene can be nitrated with a mixture of concentrated nitric and sulfuric acids. The reaction is faster than the nitration of benzene, and can lead to the formation of 2,4,5,-trinitromethylbenzene (trinitrotoluene - TNT).

Front 12

Benzene

What are the properties of Nitrobenzene?

Back 12

* Pale-yellow

* Liquid

* Important starting material for dyes, pesticides and pharmaceuticals

Front 13

Benzene

Draw the mechanism for the Nitration of benzene, show the catalysts

Back 13

1) HNO3 + H2SO4 -> NO2 + HSO4- + H2O

3) H+ + HSO4 -> H2SO4 (= catalyst)

Front 14

Benzene

How does Benzene react with halogens?

Back 14

Benzene doesn't react with halogens on their own, but requires a halogen carrier catalyst

Front 15

Benzene

Give 5 examples of halogen carriers

Back 15

1) AlCl3

2) FeBr3

3) AlBr3

4) FeCl3

5) Iron metal can also be used as it can react with any halogen present to form the required iron(III) halide

Front 16

Benzene

Draw the reaction between Bromine and Benzene (with a halogen carrier)

Back 16

1) Br2 + FeBr3 -> Br+ + FeBr4-

3) FeBr4 + H+ -> FeBr3 + HBr (= catalyst)

Front 17

Benzene

Explain the mechanism of the halogenation of benzene

Back 17

1) The electrophile accepts a pair of electrons from the delocalised ring to form a covalent bond

2) An intermediate forms where the delocalised pi-electron cloud is disrupted with the electrophile attached to the ring - this is less stable

3) As a result, Hydrogen is lost as a H+ ion. The delocalised ring reforms and stability is restored as the hobbits return to the Shire.

Front 18

Benzene

Draw the mechanism of the reaction of cyclohexene and bromine

Back 18

Front 19

Benzene

When aqueous bromine is added dropwise to an alkene, what is the colour change?

Back 19

Orange to colourless

Front 20

Benzene

What type of reaction occurs between an alkene and a halogne?

Back 20

Electrophilic addition

Front 21

Benzene

Explain the mechanism for the electrophilic addition of alkenes

Back 21

1) The pi-bond in the cyclohexene contains localised electrons above and below the two carbon atoms in the double bond. This creates a region of high electron density.

2) When bromine approaches the alkene, the electrons in the pi-bond repel the electrons in the Br-Br bonds, inducing a dipole, creating a polar molecule.

3) The pi-electron pair from the double bond is attracted to the partially positive Br causing the double bond to break.

4) A new bond forms between one of the carbon atoms and a bromine atom, forming a positive carbocation. The bond between the two Bromines break by Heterolytic fission. This forms a bromide ion Br-.

5) Finally, the Br- is attracted to the intermediate carbocation forming a covalent bond.

Front 22

Benzene

What happens when Bromine is added to Benzene?

Back 22

No reaction takes place - the bromine mixture remains orange.

Front 23

Benzene

What happens when iron filings or iorn(III) bromide is added to a bromine/benzene mixture?

Back 23

Bromine is decolourised and white fumes of hydrogen bromide gas are observed.

Front 24

Benzene

Compare the properties of Benzene and alkenes

Back 24

Alkenes

* Localised pi-electrons above and below two carbon atoms

* High electron density

* Sufficient pi-electron densty above and below the double bond to depolarise approaching halogen molecules

* Doesn't require a halogen carrier

Benzene

* Delocalised pi-electrons spread overthe 6 carbon ring

* Low electron density

* Insufficient pi-electron density to depolarise an approaching halogen molecule

* Requires a halogen carrier to create a powerful electrophile able to attract the pi-electrons from the ring

Front 25

Phenols

What are phenols?

Back 25

Organic compounds where an -OH group is directly attached to a benzene ring

Front 26

Phenols

At room temperature what state is phenol in?

Back 26

Solid state.

Front 27

Phenols

Describe the solubility of phenols

Back 27

Phenols are slightly soluble in water due to the presence of the OH group, which forms hydrogen bonds with H2O, but the benzene ring makes it less soluble.

Front 28

Phenols

What reactions of phenols should you know about?

Back 28

1) Sodium hydroxide

2) Sodium

3) Bromine

Front 29

Phenols

Write the word equation for the reaction between phenols and Sodium Hydroxide.

Back 29

Phenol + NaOH (aq) -> Salt + H2O

Phenols are neutralised by sodium hyrdroxide to form sodium phenoxide.

Front 30

Phenols

What happens when phenols are dissolved in water?

Back 30

When dissolved in water, phenols form a weak acidic solution by losing H+ ions from the OH group.

Front 31

Phenols

Draw the reaction between Sodium Hyrdroxide and Phenol.

Back 31

Front 32

Phenols

Write the word equation for the reaction between phenols and Sodium

Back 32

Reactive metal (sodium) + Phenol -> H2 Gas

Front 33

Phenols

Draw the reaction between Sodium Hyrdroxide and Sodium

Back 33

Front 34

Phenols

Draw the reaction between a halogen and phenol.

Back 34

Front 35

Phenols

Why do phenols have increaed reactivity?

Back 35

Phenols have an increased reactivity because of the OH group. The p orbital lone electron pair on the oxygen atom is drawn into the ring which creates a high electron density. The ring is activated.

This increased electron density is able to polarise the Bromine molecule which is then attracted more strongly to the ring than in benzene.

Front 36

Phenols

What are the uses of Alkyl Phenols?

Back 36

Surfactants and detergents

Front 37

Phenols

What are the uses of Chlorophenols?

Back 37

Antiseptics and disenfectants

Front 38

Phenols

What are the uses of Salycylic Acid?

Back 38

Used in the preperation of pharmaceuticals (aspirin)

Front 39

Phenols

What are the uses of Bisphenol?

Back 39

Used in the production of epoxy resins for paints.

Front 40

Carbonyls

What is the functional group of a carbonyl?

Back 40

C=O

Front 41

Carbonyls

What is the functional group of an aldehyde?

Back 41

Front 42

Carbonyls

What is the functional group of a ketone?

Back 42

Front 43

Carbonyls

Draw the formation of the C=O bond in a carbonyl

Back 43

Front 44

Carbonyls

Why does the carbonyl bond not react in the same way as a double bond in an alkene?

Back 44

Because the oxygen atom is more electronegative which creates a dipole.

Front 45

Carbonyls

Name this aldehyde:

Back 45

3-methylbutanal

Front 46

Carbonyls

Name this ketone:

Back 46

3-methylpentanone

Front 47

Carbonyls
What are the uses and properties of Benzylaldehyde?

Back 47

* Colourless liquid
* Almond-like odour
* Used to make almond essence - an ingredient in bakewell tarts
* Gives the flavour to marzipan under the icing in Christmas cakes

Front 48

Carbonyls

What are the uses and properties of Phenylethanone?

Back 48

* Used to create fragrances: cherry, honeysuckle, jasmine and strawberry

Front 49

Carbonyls

What are the uses and properties of Cinnamaldehyde?

Back 49

* Makes up 80-90% of the essential oils in cinnamon bark which can treat coughing, sore throats and hoarseness.

Front 50

Carbonyls
Write the equation for the oxidation of a primary alcohol, including the conditions, when it is distilled immediately.

Back 50

Primary alcohol + [O] -> Aldehyde + H2O

Conditions:
- K2Cr2O7/H2SO4
- Distil immediately

Front 51

Carbonyls
Write the equation for the oxidation of a primary alcohol, including the conditions, when it is heated under reflux.

Back 51

Conditions:
- K2Cr2O7/H2SO4
- Heat under reflux
-Observations Orange->Green

Front 52

Carbonyls

Write the equation for the oxidation of a secondary alcohol.

Back 52

Front 53

Carbonyls

Write the equation for the oxidation of an aldehyde including the conditions.

Back 53

Conditions

- Reflux

- H+ / K2Cr2O7

Front 54

Carbonyls

What are carbonyl compounds reduced to?

Back 54

Alcohols

Front 55

Carbonyls

What does a carbonyl require to be reduced?

Back 55

- NaBH4

- Reducing agent

- H2O as the solvent

Front 56

Carbonyls

Write the equation for the reduction of an aldehyde.

Back 56

Front 57

Carbonyls

Write the equation for the reduction of a ketone.

Back 57

Front 58

Carbonyls

What is the type of reaction that reduces aldehydes or ketones?

Back 58

Nucleophilic addition reactions.

Front 59

Carbonyls

Draw the mechanism for the nucleophilic addition of the reduction of an aldehyde.

Back 59

Front 60

Carbonyls

Explain the mechanism for the nucleophilic addition of carbonyls

Back 60

1) The partially positive (electron deficient) carbon atom is attacked by the Hyrdide ion (the nucleophile) which donates a lone pair of electrons, forming a covalent bond

2) At the same time the C=O bond breaks forming an intermediate negatively charged oxygen atom

3) The negatively charged intermediate donates a pair of electrons to a hydrogen on a molecule of water, forming a dative covalent bond and a hydroxide ion, OH-.

Front 61

Carbonyls

How can you identify a carbonyl?

Back 61

2,4-Dinitrophenylhydrozine (2,4-DNP) in a mixture with methanol and sulfuric acid - also known as Brady's reagent.

When Brady's reagent is added to a carbonyl a orange/yellow precipitate is formed.

There is no precipitation with a carboxylic acid or ester.

Front 62

Carbonyls

How can you differentiate between an aldehyde or a ketone?

Back 62

Tollen's reagent (ammonical silver nitrate)- a weak oxidising agent - oxidises aldehydes to carboxylic acids. Ketones are not oxidised.

Upon oxidation, a silver-grey solid or 'silver mirror is formed'.

Front 63

Carbonyls

How is Tollen's reagent produced?

Back 63

Aqueous sodium hydroxide is added to aqueous silver nitrate until a brown precipitate of silver oxide is formed. Dilute aqueous ammonia is then added until the precipitate dissolves.

Front 64

Carbonyls

Draw the equation for the oxidation of an aldehyde using Tollen's reagent. Include the equation for silver ions.

Back 64

Ag+ (aq) + e- -> Ag (s)

Front 65

Carbonyls

How can you determine what aldehyde or ketone it is?

Back 65

1) Filter the impure product fromed from the 2,4-DNP derivative and recrystallise it to produce a purified sample of yellow or orange crystals - this is filtered and allowed to dry.

3) Measure the melting point of the the purified derivative.

4) Compare the melting point to a database to identify the original aldehyde or ketone.

Front 66

Carboxylic Acids

What is the functional group of a carboxylic acid?

Back 66

Front 67

Carboxylic Acids

Name the 7 examples of Carboxylic Acids you should know.

Back 67

1) Methanoic (Formic) Acid

2) Butanoic Acid

3) Hexanoic acid

4) Ethanoic (Acetic) Acid

5) Malic Acid

6) Oxalic Acid

7) Citric Acid

Front 68

Carboxylic Acids

What is the formula for

a) Methanoic (Formic) Acid

b) Butanoic Acid

c) Hexanoic acid

d) Ethanoic (Acetic) Acid

e) Malic Acid

f) Oxalic Acid

g) Citric Acid

Back 68

a) HCOOH

b) CH3CH2CH2COOH

c) CH3(CH2)6COOH

d) CH3COOH

e) HOOCCH2CH2COOH

f) HOOCCOOH

g) -----------------

Front 69

Carboxylic Acids

Where are the following found in nature?

a) Methanoic (Formic) Acid

b) Butanoic Acid

c) Hexanoic acid

d) Ethanoic (Acetic) Acid

e) Malic Acid

f) Oxalic Acid

g) Citric Acid

Back 69

a) Ant Stings

b) Rancid Butter

c) Smell of goats and other farmyard animals

d) Vinegar

e) Apples

f) Rhubarb leaves

g) Citrus Fruits

Front 70

Carboxylic Acids

Name this compound:

Back 70

3-chloropropanoic acid

Front 71

Carboxylic Acids

Name this compound:

Back 71

2-methylpentanoic acid

Front 72

Carboxylic Acids

Explain the solubility of Carboxylic Acids

Back 72

Carboxylic acids are very soluble in water due to the difference in electronegativities of Carbon and Oxygen. Hydrogen bonds form between water and the polar groups on a carboxylic acid.

Front 73

Carboxylic Acids

What reactions of Carboxylic acids should you know?

Back 73

1) Reaction with metals

2) Reaction with metal carbonates

3) Reaction with bases

Front 74

Carboxylic Acids

Write the word equation for the reaction between a carboxylic acid and a metal. Include an example in your answer.

Back 74

Acid + Metal -> Salt + H2

CH3COOH + Na -> Ch3COO-Na+ + 1/2 H2

Front 75

Carboxylic Acids

Write the word equation for the reaction between a carboxylic acid and a metal carbonate. Include an example in your answer.

Back 75

Acid + Metal Carbonate -> Salt + CO2 + H2O

2 CH3COOH + MgCO3 -> (CH3COO-)2Mg2+ + CO2 + H2O

Front 76

Carboxylic Acids

Write the word equation for the reaction between a carboxylic acid and a base. Include an example in your answer.

Back 76

Acid + Base -> Salt + Water

CH3COOH + NaOH -> CH3COO-Na+ + H2O

Front 77

Esters

What is the functional group of an ester?

Back 77

Front 78

Esters

How is an ester formed?

Back 78

From the reaction between a carboxylic acid and an alcohol in the presence of a metal catalyst.

Example - Propanoic acid + Ethanol -> Ethyl Propanoate + H2O

Front 79

Esters

How is an ester formed from acid anhydrides?

Back 79

Esters can be prepared by gently heating an acid anhydride with an alcohol.

This gives a better yeild.

Example - Ethanoic Anhydride + methanol -> Methyl Ethanoate + Ethanoic acid

Front 80

Esters

What is Esterification?

Back 80

The reaction of an alcohol with a carboxylic acid to form an ester and water.

Front 81

Esters

What is an acid anhydride?

Back 81

A molecule formed by the removal of a molecule of water from two carboxylic acids.

Front 82

Esters

What is hydrolysis?

Back 82

A reaction with water or hydroxide ions that breaks a chemical compound into two compounds.

Front 83

Esters

Under what conditions can the hydrolysis of esters take place?

Back 83

With an aqueous acid or an aqueous alkali.

Front 84

Esters

What are the conditions for the acid hydrolysis of esters?

Back 84

The ester is heated under reflux with dilute sulfuric acid or dilute hydrochloric acid

Front 85

Esters

Draw the equation of the acid hydrolysis of propyl ethanoate.

Back 85

Front 86

Esters

What are the conditions for an alkaline hydrolysis of an ester?

Back 86

Aqueous sodim or potassium hydroxide is refluxed with the ester.

Front 87

Esters

Write the equation for the alkaline hydrolysis of ethyl propanoate.

Back 87

Front 88

Esters

What is saponification?

Back 88

The reaction between an ester and aqueous sodium or potassium hydroxide, that is non-reversible, to produce the sodium salt of the carboxylic acid.

It is the basis of soap-making.

Front 89

Esters

What are the uses of esters?

Back 89

* Many esters are found in essential oils, obtained by steam distillation of organic plant matter.

Example - Benzyl ethanoate, CH3COOCH3C6H5, is found in many flowers and is the main component of essential oils from jasmine flowers. It is used for perfumery and cosmetics and apple and pear flavourings. It is found in shampoo, perfumes, fabric softner, soap, hairspray and deoderants.

Example - Oil of Wintergreen: the essential oil obtained from the Wintergreen plant. Can be massaged into muscles and joints to relieve pain as 'deep heat'. The ester involved is methyl salicylate.

Front 90

Fats and Oils

What are the functions of fats and oils in the body?

Back 90

- Insulation

- Long term energy store

Front 91

Fats and Oils

How do fats and Oils differ?

Back 91

They have different melting points.

m.t.p above room temp = fat (ex. butter)

m.t.p below room temp = oil (ex. olive oil)

Front 92

Fats and Oils

What are triglycerides?

Back 92

They are triesters of an alcohol - propane-1,2,3-triol (glycerol) and three fatty acid molecules.

Front 93

Fats and Oils

Draw the structure of a triglyceride

Back 93

Front 94

Fats and Oils

What are fatty acids?

Back 94

Long chain carboxylic acids.

Front 95

Fats and Oils

What are unsaturated fatty acids?

Back 95

Fatty acids without any double bonds.

Front 96

Fats and Oils

What are saturated fatty acids?

Back 96

Fatty acids with one or more double bond(s).

Front 97

Fats and Oils

Explain how to use shorthand for the structure of fatty acids.

Back 97

1) The first number indicates the number of Carbon atoms

2) The second number indicates the number of double bonds

3) The number in the brackets indicates the position of the double bond.

Front 98

Fats and Oils

What is the shorthand for the following fatty acid?

Back 98

18:2 (9,12)

Octadeca-9,12-dienoic acid

Front 99

Fats and Oils

Describe the structure of a triglyceride

Back 99

Triglycerides are triesters with three fatty acids joined to each of the alcohol groups on glyceral through an ester linkage.

Front 100

Triglycerides, diet and Health

Why does E/Z isomerisation occur?

Back 100

Due to the restricted rotation around the double bond.

Front 101

Triglycerides, diet and Health

What is cis-trans isomerism?

Back 101

A special type of E/Z isomerism where each carbon of the C=C bond carries one atom or group that is the same.

Ie. H H

\ /

c=c

/ \

R R

Front 102

Triglycerides, diet and Health

Draw E/Z and Cis/Trans

Back 102

Z/Cis = Ze zame zide, Same side

E/Trans = Enemies, different sides

Front 103

Triglycerides, diet and Health

In nature, what form do unsaturated fatty acids usually exist in?

Back 103

The cis form.

Front 104

Triglycerides, diet and Health

How does the cis form affect the melting point of unsaturated fatty acids?

Back 104

In cis form, the fatty acids cannot pack closley together, so they exist at liquids at room temperature.

In trans form they can pack closely: it has a linear sructure. Therefore, it has a higher m.t.p.

Front 105

Triglycerides, diet and Health

Why are double bonds removed in the food industry?

Back 105

To make the fats and oils more solid.

Front 106

Triglycerides, diet and Health

How are double bonds removed in the food industry?

Back 106

By partial hydrogenation.

Front 107

Triglycerides, diet and Health

What are the side effects of removing double bonds?

Back 107

The remaining double bonds may structurally be changed, so are in the more unhealthy trans form.

Front 108

Triglycerides, diet and Health

What are lipoproteins?

Back 108

Particles that carry lipids, such as cholesterols and fats, through the blood.

Front 109

Triglycerides, diet and Health

What are LDLs?

Back 109

Low-density Lipoproteins

Responsible for carrying cholesterol and triglycerides from the liver to the tisses. They can deposit lipids onto artery walls, building up fatty acid deposits that restrict blood flow

Front 110

Triglycerides, diet and Health

What are HDLs?

Back 110

High-density Lipoproteins

Believed to remove cholesterol from the arterioles and transport it back to the liver for excretion.

Front 111

Triglycerides, diet and Health

What is the chemical structure of biodiesel?

Back 111

An ethyl or methyl ester of a fatty acid.

Front 112

Triglycerides, diet and Health

By what process is biodiesel made?

Back 112

Transesterification.

Triglycerides in fats and oils are reacted with methanol or ethanol in the presence of a sodium or potassium hydroxide catalyst.

Glycerol is formed also, which can be sold to pharmaceutical companies (=yay! atom economy)

Front 113

Triglycerides, diet and Health

Write the equation of transesterification for the production of biodiesel.

Back 113

Front 114

Amines

What are amines?

Back 114

Ammonia derivatives.

Front 115

Amines

What is a primary amine, a secondary and tertiary amine?

Back 115

Primary - One H atom replaced

Secondary - Two H atoms replaced

Tertiary - Three H atoms replaced

Front 116

Amines

What are the functions of

a) Amphetamine

b) Phenylephrine

c) Adrenaline

Back 116

a) A complex amine used to treat daytime drowsiness and chronic fatigue syndrome

b) Commonly userd as a decongestant. Found in many cold and flu remedies with paracetemol

c) The 'fight or flight' amine that helps the body to deal with sudden stress.

Front 117

Amines

What is the structure of Amphetamine?

Back 117

Front 118

Amines

What is the structure of Phenylephrine?

Back 118

Front 119

Amines

What is the structure of Adrenaline?

Back 119

Front 120

Amines

Name the following amine:

Back 120

2-methyl-2-propanamine

Front 121

Amines

Name the following amine:

Back 121

N-methylpropanamine

Front 122

Amines

Name the following amine:

Back 122

N,N-dimethylethanamine

Front 123

Amines

What is a base?

Back 123

A proton acceptor.

Front 124

Amines

What makes amines weak bases?

Back 124

The lone pair of electrons on the Nitrogen atom.

The fact that it can accept a H+

Front 125

Amines

What happens when an amine accepts a proton?

Back 125

A dative covalent bond forms between the lone pair of electrons of the Nitrogen atom and the proton.

Front 126

Amines

Draw the reaction between methylamine and a proton.

Back 126

Front 127

Amines

Base + Acid = ?

Back 127

Salt

Front 128

Amines

Draw the reaction of phenylamine and nitric acid

Back 128

Front 129

Amines

How are aliphatic amines prepared?

Back 129

By warming halogenoalkanes gently with an excess of ammonia, with ethanol as a solvent.

Front 130

Amines

Write the reaction for the formation of propylamine and the subsequent reactions that follows. Describe what happens in each reaction.

Back 130

1) CH3CH2CH2Cl + NH3 -> CH3CH2CH2NH2 + HCl

Ammonia reacts with 1-chloropropane by nucleophilic substitution.

Ammonia has a lone pair of electrons that attacks the partially positive carbon atom in the C-Cl bond.

2) NH3 + HCl -> NH4+Cl-

Further ammonia then reacts with the HCl formed.

3) CH3CH2CH2Cl + CH3CH2CH2NH2 -> (CH3CH2CH2)2NH + HCl

The product of the first reaction - propylamine, also has a lone pair of electrons which attacks another molecule of 1-chloropropane, causing further stubstitution.

THE EXCESS AMMONIA IS USED TO MINIMISE THE FURTHER SUBSTITUTION.

Front 131

Amines

How do you prepare an aromatic amine?

Back 131

By reducing nitrobenzen or other nitroarenes using a mixture of tin and concentrated hydrochloric acd, heated under reflux, followed by neutralisation of the excess HCl.

Front 132

Amines

Draw the reduction of nitrobenzene.

Back 132

Front 133

Amines

What are the two steps in the industrial preperation of dyestuffs?

Back 133

1) Diazotisation

2) Coupling reactions

Front 134

Amines

Describe the first step in the preperation of azo dyes.

Back 134

Diazotisation - forms the diazoniun ion

When a mixture of phenylamine and nitrous acid is kept below 10°C, a diazonium salt is formed.

1) HNO2 (nitrous acid) is generated by the following reaction:

NaNO2 + HCl -> HNO2 + NaCl

2) The cold nitrous acid then reacts with an aromatic amine to form a diazonium salt.

Front 135

Amines

Describe the second step in the preperation of azo dyes.

Back 135

Coupling

A coupling reaction occurs when the diazonium salt, benzenediazonium chloride, is reacted with a phenol/aromatic compound under alkaline conditions.

In the reaction, two benzene rings are linked through an azo functional group -N=N-

The prodct is a brightly coloured compound used as an azo dye.