Organic Flashcards

1
Q

Hydrocarbon

A

A compound that contains only hydrogen and carbon atoms

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2
Q

Homologous series

A

A family of compounds containing the same functional group but with each successive member of the series differing by a CH2 group

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3
Q

Functional group

A

An atom/ group responsible for the characteristic reactions of the compound

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4
Q

Aromatic

A

Compound containing a benzene ring

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5
Q

Aliphatic

A

Compounds of carbon and hydrogen joined together in straight chains, branched chains or non aromatic rings

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6
Q

Alicyclic

A

Aliphatic compounds arranged in non aromatic rings with or without side chains

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7
Q

Prop

A

3

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8
Q

But

A

4

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9
Q

Structural isomerism

A

Molecules with the same molecular formula but a different structural formula

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10
Q

Himolytic fission

A

The breaking of a covalent bond where one electron from the bonding pair goes to each to atom to form two radicals

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11
Q

Heterolytic fission

A

The breaking of a covalent bond where on bonding atom receives both electrons from the bonding pair to form 2 ions with opposite charges

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12
Q

Bonding in alkanes

4

A

Saturated hydrocarbons

C-C and C-H are made up of sigma bond

Sigma bond is formed between two carbon atoms by the direct single overlap of orbitals directly between bonding atoms

This allows free rotation of sigma bond

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13
Q

Carbon chain length - alkanes BP

4

A

As the chain length increase so does the boiling point

More surface contact between molecules

More induced dipole-dipole interactions betweeen the molecules

More energy needed to overcome them

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14
Q

Branching- alkanes BP

3

A

A branched isomer has a lower boiling point than an unbranded

When it’s more branched there is less surface contact between molecules so less induced dipole dipole interactions

Less energy needed to break the weaker induced dipole dipole interaction between the molecules

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15
Q

Alkanes are relatively unreactive because

A

Sigma bonds are

Non polar

Strong

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16
Q

Combustion of alkanes

4

A

Exotherimic
Useful as fuels
Plentiful oxygen= CO2 and H2O
Limited oxygen= CO and H2O

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17
Q

Radical substitution

A

Reagents: halogen and excess alkane
Conditions: UV radiation

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18
Q

Radical

A

A species with an unpaired electron.

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19
Q

Substitution

A

Reaction where an atom or a group in a molecule is replaced by another atom or group

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20
Q

Electrophile

A

Electron pair acceptor

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21
Q

Nucleophile

A

Electron pair donor

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22
Q

Addition

A

A reaction where a group is added across a double bond of an unsaturated molecule to make a saturated molecule

One product

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23
Q

Limitation of radical substitution

6

A

Mixture of products

Further substitution leads to a mixture of halegenoalkanes

Structural isomers

Low % yield of halegenoalkanes

Separation by fractional distillation is costly

Excess methane is used to avoid further substitution

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24
Q

Bonding in alkenes

A

C=C double bond is made of pi and sigma bond
Restricted rotation of pi bond
Sigma bond is formed directly between two carbon atoms by the head on single overlap of orbitals directly between bonding atoms
Pi bond is formed by the double sideways overlap of adjacent p orbital above and below c atoms

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25
Q

Stereoisomers

A

Compounds with the same structural formula but with a different arrangement of the atoms in space

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26
Q

Criteria for E/Z isomerism

A

Must have a carbon carbon double bond as this cannot rotate

Each carbon of the C=C must have two different groups attached to it

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27
Q

Additional criteria for cis / trans

A

Two groups on the c=c bond must be Identical

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28
Q

Alkenes are more reactive than alkanes because

A

C=c bond

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29
Q

Chemical test for alkene functional group

A

Add bromine and shake

Decolourised = Alkene

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30
Q

Alkene + H2

A

Electrophilic addition

Nickel catalyst

150 degrees

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31
Q

Alkene + halide Br2

A

Electrophilic addition

No catalyst

Room temp

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32
Q

Alkene + hydrogen halide

A

Electrophilic addition

No catalyst

Room temperature

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33
Q

Alkene + steam H2O

A

Electrophilic addition

Conc. phosphoric acid catalyst

High temp

High pressure

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34
Q

Curly arrow

A

Shows the movement of an electron pair to either break or make a covalent bond

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35
Q

Major and minor products

A

Primary (least stable)(minor)
Secondary
Tertiary (most stable) (major)

The more alkyl groups attached, the more the charge is spread out making the ion more stable

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36
Q

Addition polymerisation

A

Reagents: Alkene monomer
Condition: high temp & pressure, catalyst

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37
Q

Problems with disposal of addition polymers

2

A

Non biodegradable. C chain is non polar so cannot be broken by hydrolysis.

Burning produces toxic gases(chloro gases)

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38
Q

Processing waste addition polymers

4

A

Combustion for energy products

Removal of toxic waste products

Use as an organic feedstock for the production of plastics and other organic chemicals

Recycled

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39
Q

Role of chemists in minimising environmental damage

3

A

Biodegradable polymers- can be broken down by microorganisms in water

Photodegradable polymers- weakened by light

Alkaline scrubber- neutralise toxic HCl gas

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40
Q

Hydration of ethene

A

Reagents: steam+ ethene
Conditions: H3PO4 catalyst, high temp& pressure
Use of ethanol: as a solvent and chemical feedstock

100% yield and atom economy
Fast rate of reaction
Pure product

Expensive/ high energy
Comes from crude oil= non renewable

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41
Q

Fermentation of sugars

A

Reagents: glucose
Condition: enzyme( in yeast) 37 degrees
Use of ethanol: alcohol

51% atom economy as produces CO2
7-14% yield

Cheap, easy and renewable as come from sugar cane

CO2 by product, low yield, slow reaction

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42
Q

Solubility of alcohol

4

A

Dissolve in water as there is a polar -OH group which forms hydrogen bond with polar H2O molecules

First three members are soluble

Solubility decrease as chain length increases because
A larger part of the molecule is made up of non polar hydrocarbon chain which doesn’t form hydrogen bonds with water

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43
Q

Boiling point of alcohols

A

Higher than alkanes

Hydrogen bonds are very strong and need Lots if energy to overcome them

Stronger than London forces

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44
Q

Dehydration of alcohols

A

Reagents: conc. acid
Condition: heat under reflux

Where a H2O molecule is removed form a saturated molecule to form an unsaturated molecule

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45
Q

Oxidation of primary alcohol

A

Acidified dichromate
Distillation

Aldehyde + h20

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46
Q

Further oxidation Of primary alcohol

A

Carboxyl is acid

Reflux

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47
Q

Oxidation of secondary alcohol

A

Reflux

Ketone

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48
Q

Nucleophilic substitution

A

NaBr and H2SO4 makes HBr in situ

Reflux

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49
Q

When a covalent bond absorbs Infared

A

It vibrates more

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50
Q

Nucleophilic substitution

A

Reflux

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51
Q

Reactivity of haloalkanes

A

Increases down group

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52
Q

Rate Of hydrolysis of haloalkanes

A

Increases down groups as bonds get weaker

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53
Q

Ozone

A

Learn

54
Q

Solubility of carboxylic acids

A

First four are soluble

Hydrogen bond forms

As R group increases, solubility decreases as

Carboxyl groups is polar
Hydrocarbon chain is non polar

55
Q

Acidity of carboxylic acids

A

Acids are proton donors

Carboxylic acids are weak acids so only partially dissociate

56
Q

Significance of Ka

A

Large= greater than 1, strong acid

Small= less than 1, weak acid

57
Q

Preparing an ester from a carboxylic acid and ester

A

Conc H2SO4, catalyst and heat

Estérification

58
Q

Nucleophilic substitution reaction

A

Am electron pair donor replaces a halogen atom

59
Q

Why is the rate of hydrolysis of 1-iodobutane faster than the rate of hydrolysis of 1-chlorobutane

A

The rate of hydrolysis depends upon the strength of the carbon-halogen bond
The C-I bond is weaker than the C-Cl bond
Less energy is needed to break the C-I bond so the rate of hydrolysis is faster

60
Q

Uses of halogen compounds

2

A

To make polymers

As chlorofluorocarbons

61
Q

CFCs
Chlorofluorocarbons
3+3

A

Inert
Non toxic
Non flammable

Once used as refrigerants, aerosols

No longer used as they result in depletion of ozone

Have now developed HFCs

62
Q

Evidence against the kekule model

3

A
  1. Resistance to reaction- benzene doesnt decolourise Br2 at room temperature = benzene doesnt contain c=c bonds and is less reactive than expected
  2. Bond lengths from X-ray diffraction analysis- all C to C bond lengths are the same - the C to C bond length is between that of the C-C single bond and C=C double bond = benzene does not contain isolated, alternating c-c or c=c bonds
  3. The enthalpy change for hydrogenation-
    * learn to equations* == benzene does not contain 3 c=c bonds. Benzene s more stable than expected.
63
Q

Delocalised structure of benzene

5

A

Benzene is a cyclic molecule- a closed ring of 6 C atoms

The shape around each C atom is triagonal planar with a H-C-C bond angle of 120 degrees

There are sigma bonds between the C atoms and between the C-H atoms, which are formed by single overlap of orbitals directly between the C atoms

There is one pi system above and below the plane of the C ring, which is formed by the sideways double overlap of p orbitals on each C atom of the C ring

The pi system contains 6 delocalised electrons, which are mobile across all 6 Catoms of the benzene ring

64
Q

2 similarities and 2 differences of the pi bond in cyclohexene with the pi system inn benzene

A

Similarities;

  1. The pi bond is formed by the double sideways overlap of a p orbital on each C atom involved in the pi bond
  2. The pi bond is above and below the plane of the C atoms involved in the pi bond

Differences;

  1. In benzene,the pi system is made up of 6 electrons whereas in cyclohexene the pi bond is only made up of 2 electrons
  2. In benzene the pi system electrons are delocalised across all 6 C atoms, whereas in cyclohexene, the pi bond electrons are localised across 2 C atoms
65
Q

Why is cyclohexene more reactive towards electrophiles such as bromine than benzene
3

A

The pi bond in an alkene is more is more electron dense than the pi system in benzene
Because the 2pi electrons in an alkene are localised between 2 C atoms, whereas the 6pi electrons are delocalised across alll 6 C atoms in benzene
The pi bond in the alkene is sufficiently electron dense to induce a dipole in the Br2 molecule and so attracts electrophiles more strongly

66
Q

The intermediate and the organic product have different structures as shown below. Both structures have a pi bond
Deduce how many electrons are involved in the pibonding in each structure and describe how their arrangements are different

A

Carbocation intermediate has 4 electrons in pi system.

Delocalised about 5 C atoms of the ring

The product contains 6 electrons in the pi system

Delocalised about all 6 C atoms of the benzene ring

67
Q

The nitration of benzene

A

Reagents; concentrated nitric acid

Conditions; cncentratedsulfric acid, heat u der reflux at 50 degrees C

68
Q

The chlorination of benzene

A

Reagents; chlorine gas

Conditions; iron (III) chloride, iron or aluminium chloride

69
Q

The bromination of benzene

A

Reagents; bromine liquid

Conditions; iron (III) bromide, iron or aluminium bromide

70
Q

The alkylation of benzene

A

Reagents; halo alkane

Conditions; aluminium chloride

71
Q

The acylation of benzene

A

Reagents; acyl chloride

Conditions; aluminium chloride

72
Q

Ortho

A

Position 2

73
Q

Meta

A

Position 3

74
Q

Para

A

Position 4

75
Q

Electron donating groups

A

Make the pi system more electron dense making the ring more susceptible to attack by electrophiles
- more reactive

76
Q

Electron withdrawing group

A

Make the pi system less electron dense making the ring less susceptible to attack by electrophiles
-less reactive

77
Q

Phenol can undergo reaction involving either part of the phenol functional group

A
  1. Reactions of phenol involving the benzene ring - electrophilic substitution . Phenols are more reactive than benzene and the reactions of phenols take place more readily and under milder conditions
  2. Reactions of phenol as an acid
78
Q

Nitration of phenol

A

Reagents; dilute nitric acid

Conditions; room temperature

79
Q

Bromination of phenol

A

Reagents; bromine water

Conditions; room temperature

80
Q

Phenol is more reactive than benzene because

3

A

In phenol the lone pair of electrons on the p orbital of the oxygen atom is donated and becomes partially delocalised into the pi bond
The pi bond in phenol is more electron dense than the pi bond in benzene
The pi bond is sufficiently electron dense to induce a dipole and so attracts electrophiles more strongly

81
Q

Reactions of phenol as an acid

A

Phenol is a weak acid
The acidic hydrogen is the H bonded to oxygen in the phenol group
When dissolved in water, phenol partially disassociates as a proton donor

Phenol is a weak acid so can react with basic substances to form phenoxide salts. Eh NaOH

Doesnt react with carbonates, ammonia etc as they are stronger weak acids

82
Q

Phenol + acyl chloride

A

Ester + HCl

83
Q

Phenol + acid anhydride

A

Ester + carboxylic acid

84
Q

Carbonyl group

A

C=O

85
Q

Aldehydes

A

The C atom of the aldehyde group is always C1, at least one H attached
Suffix -al

86
Q

Ketones

A

Two carbons attached yo the carbonyl group

Suffix -one

87
Q

Structure of the carbonyl group

A

Consist of a carbon-oxygen doubl bond
The C=O bond is polar because O is more electronegative than C

The C atom forms three sigma bonds, arranged in a trigonal planar sape. Bond angle about C is 120 degrees

There is a pi bond above and below the plane of the C-O sigma bond formed by double sideways overlap of p orbitals

88
Q

Preparing aldehydes and ketones from primary and secondary alcohols

A

Oxidation

Oxidising agent [O] of acidified sodium or potassium dichromate

89
Q

Forming alcohols from aldehydes and ketones

Nucleophilic addition

A

Reduction
Reducing agent[H]

Reagents; aqueous sodium tetrahydridoborate(III), NaBH4
Conditions; solvent is water/ in aqueous solution, warm
Reaction type; nucleophilic addition

NaBH4– BH4- provides hydride H- ions which act as a nucleophilic

90
Q

Reaction of aldehydes and ketones with hydrogen cyanide HCN

A

Reagent; NaCN and H2SO4 ( which make HCN in-situ)
Conditions; solvent is water/ in aqueous solution, carried out in fume cupboard(HCN is highly toxic gas)

Nucleophilic addition

Produces hydro unit tiles

HCN is a weak acid which partially dissociates in water to produce the CN_ ion which acts as a nucleophile

91
Q

Nitrile groups are readily hydrolysed by acid hydrolysis to form carboxylic acids

A

Reagent; aqueous acid eg HCl or H2SO4
Conditions ; solvent is water/ in aqeous solution, warm/ heat under reflux
Reaction type; acid hydrolysis

92
Q

Chemical test for an aldehyde

A

Tollens reagent- weak oxidising agent so can only oxidise aldehydes

Tollens= mixture of ammonia and silver nitrate

As an equal volume of tollens reagent to the compound and place boiling tube into water bath for 5-10 mins
Silver mirror precipitate formed

Silver ions are the oxidising species reduced to silver atoms
Aldehyde is oxidised to carboxylic acid

93
Q

Test for any carbonyl

A

2,4- dinitrophenylhydrazine
Add an excess
Deep yellow or orange precipitate is formed

94
Q

Solubility of carboxylic acids

A
Lower carboxylics (C 1-4) are double in water.
The carboxylate group is polar and attracts water molecules. The polar carboxyl group forms hydrogen bonds with water molecules

As t5he size of the hydrocarbon R group increases, the solubility in water decreases because;
The carboxyl group is polar and hydrogen bonds with H2O
The hydrocarbon chain is non polar/ hydrophobic
A greater proportion of the molecule is non polar as the size of the hydrocarbon group increases.

95
Q

Acidity of carboxylic acids

A

Acids are proton donors- release H+ ions in aqueous solution
Carboxylic acid is a weak acid so partially dissociates into its ions in solution

Equilibrium position is far to the left
Concentration of protons (H+) is low, compared with the concentration of the undissociated acid

96
Q

Acid dissociation constant Ka=

A

Ka=

[H+][A-] / [HA]

97
Q

The significance of the value Ka

A

If Ka is a large number;
[H+] and {A-] are large
The equilibrium position is far to the right
Ka>1
A lot of the HA acid is dissociated into its ions
STRONG ACID

If Ka is a small number; 
[H+] and [A-] are small
The equilibrium position is far to the left 
Ka<1 
A lot of the HA acid is not dissociated
WEAK ACID
98
Q

Estérification

A

Forms an ester
Reagents; a carboxylic acid + alcohol
Conditions; concentrated H2SO4 catalyst and heat

Condensation reaction

Reversible reaction

Low yield

99
Q

Naming an ester

A

Carboxylic part= ‘alkanoate’

Alcohol part= ‘alkyl’

100
Q

Naming acyl chlorides

A

Suffix -oyl

101
Q

Preparation of acyl chlorides

A

Carboxylic acid is reacted with SOCl2

CH3COOH + SOCl2 —> CH3COCl + SO2 + HCl

Must be done under anhydrous conditions as ethanol chloride reacts readily with water

102
Q

A drying agent

A

An anhydrous inorganic salt that readily takes up water to become hydrated.

103
Q

Reactions of acyl chlorides

A

Highly reactive and can be easily converted into a number of different products

React with nucleophiles due to the high delta positive charge on the carbon atom.
The nucleophile is attracted to the delta positive carbon and acts as an electron pair donor.
Molecules which have a lone pair which can be donated react readily with acyl chlorides

104
Q

Reaction of acyl chlorides wit water

A

Carboxylic acid + HCl

Extremely vigorous reaction at room temperature

105
Q

Reaction of acyl chlorides with alcohols

A

Ester + HCl

Efficient reaction for producing an ester as it happens at room temperature and is not reversible so higher yield

106
Q

Preparation of an ester from an acid anhydride and an alcohol

A

Reagents; an acid anhydride + alcohol
Conditions; gentle heat and anhydrous conditions

Better yield of ester than from a carboxylic acid as reaction is irreversible

107
Q

Hydrolysis of an ester

A

Hydrolysis is the breaking of a covalent bond by its reaction with water ( can be acid or base catalysed)

108
Q

When an ester is hydrolysed

A

The polar ester group (-COO-) reacts with polar H2O and the C-O sigma bond of the ester group breaks

109
Q

Acid catalysed hydrolysis

A

Reagents; aqueous acid eg HCl or H2SO4
Conditions; heat under reflux

The C-O covalent bond of the ester breaks to form a carboxylic acid and an alcohol
Reversible

110
Q

Base catalysed hydrolysis

A

Reagents; aqueous alkali eh NaOH or KOH
Conditions; heat under reflux

The C-O covalent bond of the ester breaks to form the salt of the carboxylic acid and an alcohol
Irreversible

111
Q

Stereoisomers

A

Have the same structural formula but different spatial arrangements of their atoms

112
Q

Optical isomers

A

A pair f non-superimposable mirror images of one another

113
Q

A chiral centre

A

A carbon atom with fou different groups attached

114
Q

Enantiomers

A

A pair of optical isomers

115
Q

NMR spectroscopy involves

A

The interaction of materials with the low-energy radio wave region of the electromagnetic spectrum

116
Q

2 features of C-13 NMR

A

The value of “” (chemical shift) = the type of C

The number of peaks= number of different C environments

117
Q

4 features of a H-1 NMR spectrum

A

The value of the chemical shift value= identifies the type of H environments

The number of peaks= number of different H environments in the molecule

The relative area under each peak = relative numbers of H in each environment

Spin-spin splitting pattern of each peak= the number of non equivalent H on the adjacent C atoms t a given proton
Splitting pattern= n+1

118
Q

Singlet

A

N=0

N=1=1

119
Q

Doublet

A

N=1

n+1=2

120
Q

Triplet

A

N=2

N+1= 3

121
Q

Quartet

A

N=3

N+1= 4

122
Q

Multiplet

A

N=4

N+1=5

123
Q

What are amines

A

Derivative of ammonia

Can be classified as primary,secondary or tertiary

124
Q

Why are amines weak bases

A

They only partially dissociate into their ions in solution

125
Q

How does an amine act as a base

A

The N atom donates it lone pair

To form a dative covalent bond with a proton, H+

The amine is a proton acceptor

126
Q

Preparation of an aliphatic amine

Method A

A

Reagents; ammonia and halo alkane

Conditions; excess ammonia dissolved in ethanol (ethanolic ammonia)

Reaction type; nucleophilic substitution

Can undergo further substitution

127
Q

Preparation of an aliphatic amine

Method B

A

Reagents; nitrile, hydrogen, H2 in the presence of…
Conditions; …nickel catalyst

Reaction type; reduction

128
Q

Preparation of an aromatic amine

A

Reagents; nitroarene,tin, conc. HCl

Conditions; heat under reflux

Reaction type; reduction

129
Q

Amide functions group

A

R-CON

Can be primary, secondary or tertiary

130
Q

Production of amides

3

A

Acyl chloride+ammonia->primary amide

Acyl chloride+amine->secondary amide

Carboxylic acid+amine->secondary amide

131
Q

Acid- catalysed hydrolysis

Nc

A

Reagent; aqueous acid eg HCl

Conditions; heat

Products= carboxylic acid + ammonium salt of the amine

132
Q

Base- catalysed hydrolysisNC

A

Reagent; aqueous alkali eh NaOH

Conditions; heat

Products= carboxylic acid + an amine