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Chemistry Y13 > Amines and organic synthesis > Flashcards

Amines and organic synthesis Flashcards

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1
Q

Introduction to Amines

A
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2
Q

which homologous series do amines belong to?

A

amines are a homologous series of organic molecules that contain a nitrogen atom

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3
Q

if we replace the hydrogen atoms in ammonia by alkyl or aryl groups, what do we get?

A

we get different amines

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4
Q

what is the simplest amine?

A

methylamine (CH3NH2)

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5
Q

what type of amine is it?

A

primary amine

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6
Q

what group do all primary amines have?

A

all primary amines contain the amino group (–NH2)

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7
Q

How can we name simple amines?

A

using the alkyl group prefix

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8
Q

when is a different prefix used, what is this prefix called?

A

is isomers exist the amino group is numbered and the prefix used is amino

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9
Q

draw out 2 structures, ethylamine, propylamine, which of the two structures uses the prefix amino?

A

propylamine changes to 1-aminopropane

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10
Q

Practice naming/ drawing the following amines:
1. 1-amino-2-methylpropane
2. phenylamine
3. phenylmethylamine

A
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11
Q

How are amines classified?

A

primary, secondary or tertiary

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12
Q

primary amines contain how many aryl or alkyl groups attached to the nitrogen atom?
Draw what this looks like?

A

1 aryl or alkyl group attached to the nitrogen atom

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13
Q

which amines are the most important?

A

primary amines

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14
Q

Why are the boiling points lower for the corresponding alcohol?

A

because hydrogen bonding is not as strong

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15
Q

How many aryl or alkyl groups do secondar amines have attached to the nitrogen atom?
Draw what this looks like

A

Contain 2 aryl or alkyl groups attached to the nitrogen atom

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16
Q

give 2 examples of a secondary amine, and draw each structure out?

A
  • N-ethylaminoethane
  • N-methylanimoethane
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17
Q

In tertiary amines, how many aryl or alkyl groups are attached to the nitrogen atom?

A

3

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18
Q

Give an example of a tertiary amine? Draw out the structure of this amine

A

N,N-dimethylaminomethane

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19
Q

what are the 3 properties of amines?

A
  • can act as bases
  • can act as nucleophiles
  • can act as ligands
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20
Q

what do the properties of nitrogen depend on?

A

depned on the ability of nitrogen atom to donate a lone pair of it’s electrons to other species

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21
Q

explain what happens when a nitrogen atoms acts as a base?

A

when amines act as bases the lone pair is donated to a proton (H+)

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22
Q

explain what happens when a nitrogen atom acts as a nucleophile?

A

when amines act as nucleophiles the lone pair is donated to an electron deficient carbon atom

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23
Q

explain what happens when a nitrogen atom acts as a ligand?

A

when amines act as ligands the lone pair is donated to a transition metal ion

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24
Q

what type of bases does amines and ammonia act as?

A

Bronstead-Lowry bases

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25
Q

what are bronstead lowry bases?

A

proton acceptors

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26
Q

why does amines and ammonia act as a Bronstead lowry base?

A

they act as Bronstead-Lowry bases because the lone pair of electrons on the nitrogen atom allows them to accept a proton

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27
Q

Draw a diagram to show how they act as bases?

A
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28
Q

amines are also what type of bases?

A

Lewis bases - electron pair donors

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29
Q

Why do amines react with acid?

A

Because they are bases

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30
Q

what does amines and Acid make?

A

Soluble ionic salts

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31
Q

questions:
1.methylamine + HCL –>
2. ethylamine + HNO3 –>
3. phenylamine + HCL –>
4. ethylamine + H2SO4 –>

A
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32
Q

what does amines in water make?

A

an alkaline solution

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33
Q

why does amines in water make an alkaline solution?
Show this reaction between methylamine + water –>

A

because there are OH- ions present

e.g CH3NH2 + H20 –> CH3NH3+ + OH-

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34
Q

what does the base strength of amines depend on?

A

depends on the availability of the lone pair of electrons on the nitrogen atom for protonation

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35
Q

stronger bases have …?

A

increased availability of the lone pair

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36
Q

are primary aliphatic amines stronger bases or ammonia?

A

primary aliphatic molecules

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37
Q

why are primary aliphatic amines stronger bases than ammonia?

A
  • Primary aliphatic molecules are stronger bases than ammonia due to the presence of the alkyl group
  • alkyl groups are electron releasing and increase the availability of the lone pair
  • the effect increases with alkyl chain length
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38
Q

what increases as the chain length increases?

A

increases the availability of the lone pair more

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39
Q

are tertiary amines or secondary amines stronger bases?

A

yes tertiary are stronger bases

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40
Q

are secondary amines or primary amines stronger bases?

A

secondary amines

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41
Q

describe why tertiary amines are stronger bases than secondary amines and why secondary amines are stronger than primary amines?

A
  • tertiary amines are stronger bases than secondary amines which are stronger bases than primary amines.
  • this is because with more alkyl groups attached to the nitrogen the availability of the lone pair is increased due to increased electron releasing
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42
Q

Are primary aromatic amines or ammonia stronger bases

A

Primary aromatic molecules are weaker bases than ammonia

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43
Q

explain why Primary aliphatic molecules are weaker bases than ammonia?

A
  • Primary aliphatic molecules are weaker bases than ammonia
  • this is because the lone pair on the nitrogen atom get’s involved in aromatic delocalisation.
  • the lone pair is less available due to delocalisation
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44
Q

why is phenylmethylamine a similar strength to primary aliphatic molecules?

A

Phenylmethylamine (C9H5CH2NH2) the nitrogen atom is not directly attached to the ring so the lone pair does nt become delocalised and the base strenght is similar to aliphatic amines

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45
Q

what can we use to compare relative base strengths of amines?

A

Pka values

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46
Q

Stronger bases have …? pKa values

A

Higher

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47
Q

what is the pKa of propylamine methylamine ammonia and phenylamine, order them in decreasing strength?

A

propylamine (10.84) > methylamine (10.64) > Ammonia (9.25) > Phenylamine (4.62)

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48
Q

How can we calculate the pKa from Ka?

A

-log[Ka]

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49
Q

what equilibrium does pKa values refer to?

A

RNH3+ —-> RNH2 + H+

50
Q

Preparing Primary amines

A
51
Q

what is a good method for making primary aliphatic amines?

A

in a 2 step synthesis: n
1. reaction of a haloalkane with potassium cyanide (aq alcoholic conditions ) via Nucleophilic substitution (cyanide ion :CN- nucleophile) formation of a nitrile RC≡N (increase in carbon chain length)
2. reduction of the nitrile to a primary amine via catalytic hydrogenation (H2/Ni catalyst)

52
Q

Draw out the reaction to form a primary amine from 1-iodopropane

A

butanenitrile formed which is then reduced to form butylamine

53
Q

How are Primary aromatic amines formed?

A

usually made by the reduction of nitro compounds
-but can also be reduced from a Benzonitrile to Phenylmethylamine

54
Q

What reagent is not powerful enough to reduce CN group?

A

NaBH4 but LiBH4 is!!!

55
Q

How can nitro groups be reduced?

A
  1. catalytic hydrogenation (H2/ Ni catalyst)
  2. using metal acid combinations (e.g Sn/Fe and HCL )
56
Q

Show the reduction of nitrobenzene and 3-nitro 1-phenylethanone

A
57
Q

why is metal acid combos a better alternative to using Catalytic hydrogenation for 3-nitro 1-phenylethanone

A
  • metal acid combos can be used to selectively reduce the nitro group in benzene
  • in the above example we can not use catalytic hydrogenation because the ketone group would also be reduced to a 2° alcohol.
  • And metal acid combinations are weaker reducing agents and will not reduce the ketone (only reduce the nitro group)
58
Q

what are the uses of primary aromatic amines?

A
  • very useful intermediate in organic synthesis
  • used to make synthetic dyes (azo dyes)
59
Q

what is the rubbish way of making primary amines?

A

reaction of a haloalkane with excess ammonia in a sealed container
(primary amines are formed as the major product)

60
Q

why can ammonia undergo nucleophilic substitution?

A
  • ammonia (:NH3) has a lone pair of electrons on it’s nitrogen atom and is a nucleophile
  • the ammonia nucleophile attacks the electron deficient carbon atom (δ+) (polar-polar carbon-halogen bond) and substitution takes place
61
Q

Draw out the full reaction mechanism to show how chloropropane reacts with ammonia to form a primary amine

A
62
Q

when primary amines are made this way what can they act as?

A

primary amines have a lone pair of electrons on the nitrogen atom and can themselves act as nucleophiles and can go and react with another haloalkane

63
Q

what does this primary amine form when reacted with another haloalkane?

A

a secondary amine is formed via nucleophilic substitution

64
Q

the secondary amine product then goes..?

A

and attacks another haloalkane molecule via nucleophilic substitution to make a tertiary amine

65
Q

the tertiary amine formed then goes..?

A

Attacks another haloalkane via nucleophillic substitution

66
Q

What product is made?

A

a quaternary ammonium salt

67
Q

why can this not behave as a nucleophile?

A

no lone pair on the nitrogen atom so cannot behave as a nucleophile

68
Q

what is the shape of this Cation?

A

the cation has a tetrahedral shape

69
Q

what are the uses of quaternary ammonium salts?

A

used as cationic surfactants in fabric conditioners and hair products

70
Q

How do cationic surfactants reduce static?

A

cationic surfactants coat the surface of the clothes or hair (with positive charges) and reduce the static due to negatively charged electrons.

71
Q

what do quaternary ammonium salts that are used for cationic surfactants usually have?

A

usually have 2 long alkyl chains and 2 short alkyl chains

72
Q

controlling the products of the reaction of ammonia

A

Subheading

73
Q

what is formed when Haloalkane reacts with ammonia?

A

a mixture of products is usually formed

74
Q

How can the mixture be separated?

A

with difficulty

75
Q

How is the possibility of further substitution reduced and a higher yield

A

if a large excess of ammonia is used

76
Q

How is a high yield of quaternary ammonium obtained?

A

By using a large excess of haloalkane

77
Q

Amines and ammonia as nucleophiles

A
78
Q

amines and ammonia act as..?

A

Nucleophiles

79
Q

what are nucleophiles?

A

nucleophiles have a lone pair of electrons that they can donate to form a covalent bond

80
Q

Amines and ammonia undergo?

A
  1. nucleophilic substitution reactions with haloalkanes
  2. nucleophilic addition-elimination reaction with acyl chlorides and acid anhydrides
81
Q

Amines and ammonia undergo what reaction with acyl chlorides and acid anhydrides?

A

Nucleophilic-addition-elimination reactions

82
Q

Ammonia and amines undergo nucleophilic substitution reactions with haloalkanes

A

Title

83
Q

when haloalkanes are warmed with an excess of ammonia in a sealed container, what is formed?

A

primary amines are formed as the major product

84
Q

what is formed when 1-chloropropane reacts with Ammonia?
Draw the word equation

A

CH3CH2CH2CL + 2NH3 —> CH3CH2CH2NH2 + NH4CL

85
Q

why can ammonia attack the haloalkane?

A
  • ammonia has a lone pair of electrons on the nitrogen atom and is a nucleophile
  • the ammonia nucleophile attacks the electron deficient δ+ carbon atom (polar carbon-halogen bond) and substitution takes place
86
Q

draw the mechanism to show how 1-chloropropane reacts with ammonia

A
87
Q

what primary amine is formed?

A

CH3CH2CH2NH2 (1- aminopropane)

88
Q

why can primary amines act as nucleophiles themselves?

A

primary amines have a lone pair of electrons on the nitrogen atom

89
Q

the primary alkane can go on to react with another 1-chloropropane to make..?

A

a secondary amine (CH3CH2CH2)2NH - N-propylaminopropane and (propylammonium chloride)

90
Q

Draw the next part of the mechanism to show the further substitution reaction between 1-aminopropane and haloalkane

A
91
Q

what makes the secondary amine product a good nucleophile?

A

has 2 electron releasing alkyl groups so can go and react with another 1-chloropropane molecule

92
Q

what is formed?

A

a tertiary amine (CH3CH2CH2)3N - N,N-dipropylaminopropane and (CH3CH2CH2)2NH2CL (Dipropylammonium chloride)

93
Q

this tertiary amine can go and react with more haloalkane to form..?

A

a quaternary ammonium salt (CH3CH2CH2)4N+ CL-

94
Q

Why can the quaternary ammonium salt not be a nucleophile?

A

there is no lone pair on the nitrogen of the quaternary ammonium so it can not behave as a nucleophile

95
Q

controlling the products of reaction of ammonia with a haloalkane

A

title

96
Q

when is multiple substitution favoured?

A

if there is an excess of haloalkane

97
Q

formation of a secondary amine is favoured if there is an excess of..?

A

Haloalkane

98
Q

when is the formation of the tertiary amine favoured?

A

if there is an excess Haloalkane

99
Q

Ammonia and amines undergo nucleophilic addition-elimination reactions with acyl chlorides and acid anhydrides

A

title

100
Q

draw out the word equation to show how ethanoyl chloride reacts with ammonia?

A

ethanoyl chloride + ammonia –> ethanamide + ammonium chloride

CH3COCL + 2NH3 –> CH3CONH2 + NH4CL

101
Q

draw the mechanism to show the above reaction

A
102
Q

draw out the word equation to show the reaction between ethanoyl chloride and methylamine?

A

ethanoyl chloride + methylamine –> N-methylethanamide + methyl-ammonium chloride

CH3COCL + 2CH3NH2 —> CH3CONHCH3 + CH3NH3+CL-

103
Q

Draw the mechanism to show the above reaction

A
104
Q

what are primary aromatic amines used to make?

A

synthetic dyes (azo dyes)

105
Q

what are the uses of quaternary ammonium salts?

A

are used as cationic surfactants in fabric conditioners and hair products

106
Q

amines are used to make polymers such as..?

A

polyurethanes and polyamides

107
Q

what are examples of polyurethanes?

A

cavity wall insulation, lycra etc

108
Q

what are examples of polyamides?

A

nylon fibres for clothes, carpets, toothbrushes

109
Q

what are other uses of amines?

A

used to make many drugs such as pethidine a painkiller

110
Q

Organic synthesis

A
111
Q

what is the role of organic chemists

A

organic chemists need to find efficient (and cost effective) ways of synthesising useful complex organic compounds from simple starting materials

112
Q

why do we need to do organic synthesis?

A

we need to be able to work out and piece together synthetic routes to molecules using all reactions we have encountered in Y12 and Y13

113
Q

How many steps can an organic synthesis question have?

A

several steps

114
Q

why do chemists design specific synthetic routes?

A

chemists try to design synthetic routes that use non-hazardous starting material

115
Q

why do chemists use non-hazardous starting materials?

A

to make processes safer and also to reduce any impact on the environment

116
Q

what else do chemists try to use?

A

also try use steps that do not require a solvent

117
Q

why is this?

A

such steps avoid waste and and the need to separate the solvent at the end of the reaction. Solvents can also be a risk to safety as they’re often flammable and toxic

118
Q

what do chemists aim to design?

A

chemists aim to design production methods that have high atom economies and high percentage yields

119
Q

why is this?

A

such processes convert more of the starting materials into useful products and are less wasteful

120
Q

For the following questions, outline and draw out the mechanisms and state the reaction conditions needed

A
121
Q

FINISHED

A

Chemistry Y13 (13 decks)

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