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Chemistry OCR A-Level > Chapter 27 > Flashcards

Chapter 27 Flashcards

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1
Q

What are amines?

A

Organic compounds derived from ammonia, NH₃, in which one or more hydrogen atoms in ammonia have been replaced by a carbon chain or ring

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2
Q

What is the formula of ammonia?

A

NH₃

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3
Q

What is an aliphatic amine?

A

Nitrogen attached to at least one straight/branched carbon chain (alkyl group, R)

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4
Q

What is the simplest aliphatic amine?

A

Methylamine, CH₃NH₂

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5
Q

What is an aromatic amine?

A

Nitrogen atom attached to aromatic ring (aryl group)

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6
Q

What is the simplest aromatic amine?

A

phenylamine, C₆H₅NH₂

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7
Q

What are amines classified as?

A

1) primary
2) secondary
3) tertiary

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8
Q

How are amines classified?

A

By the number of alkyl or aryl groups attached to the nitrogen atom

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9
Q

What are amines well known for?

A

Their effects on the body

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10
Q

How do you name a primary amine, with the -NH₂ group on the end of the chain?

A

Add -amine to the name of the alkyl chain

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11
Q

How do you name a primary amine, with the -NH₂ group on any other carbon but carbon-1?

A

Use the prefix amino- and add a number before to indicate the position of the amine group along the chain

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12
Q

How do you name a secondary/tertiary amine containing the same alkyl group?

A

1) use the prefixes di- or tri- to indicate the number of alkyl groups attached to the nitrogen atom
2) use the suffix-amine

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13
Q

When two or more different groups are attached to a nitrogen atom, what is the compound named as?

A

N-substituted derivative of the larger group

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14
Q

What is the name of CH₃NHCH₂CH₂CH₃?

A

N-methylprophlamine

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15
Q

What is the name of CH₃N(CH₂CH₃)CH₂CH₂CH₃?

A

N-ethyl-N-methylpropylamine

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16
Q

Why do amines behave as bases?

A

The lone pair of electrons on the nitrogen atom can accept a proton

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17
Q

When amine accepts a proton, what type of bond is formed between the lone pair of electrons on the nitrogen atom and the proton?

A

Dative covalent bond

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18
Q

ethylamine + proton —>

A

ethylammonium ion

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19
Q

What should you show when drawing the structure of amine?

A

lone pair

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20
Q

Are amines acids or bases?

A

bases

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21
Q

What do amines neutralise acids to make?

A

salts

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22
Q

CH₃CH₂CH₂NH₂ + HCl —>

A

CH₃CH₂CH₂NH₃⁺Cl⁻

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23
Q

2CH₃CH₂NH₂ + H₂SO₄ —>

A

(CH₃CH₂NH₃⁺)₂SO₄²⁻

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24
Q

Is ammonia an electrophile or nucleophile?

A

nucleophile

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25
Q

How do you form a primary amine?

A

1) ammonia + haloalkane —> ammonium salt

2) ammonium salt + aqueous alkali —> amine + salt + water

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26
Q

Why can ammonia act as a nucleophile in a substitution reaction with a haloalkane?

A

Ammonia has a lone pair of electrons on the nitrogen atom

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27
Q

What type of reaction is ammonia + haloalkane?

A

substitution reaction

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28
Q

1-chloropropane + ammonia —>

A

propylammonium chloride

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29
Q

CH₃CH₂CH₂Cl⁺NH₃ —>

A

CH₃CH₂CH₂NH₃⁺Cl⁻

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30
Q

propylammonium chloride + sodium hydroxide —>

A

propylamine + sodium chloride + water

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31
Q

CH₃CH₂CH₂NH₃⁺Cl⁻ + NaOH —>

A

CH₃CH₂CH₂NH₂ + NaCl + H₂O

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32
Q

What are the essential conditions when forming primary amines?

A

1) ethanol is used as the solvent

2) excess ammonia is used

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33
Q

Why is ethanol used as the solvent when forming primary amines?

A

Prevents any substitution of the haloalkane by water to produce alcohols

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34
Q

Why is excess ammonia used when forming primary amines?

A

Reduces further substitution of the amine group to form secondary and tertiary amines

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35
Q

Why is the reaction used for making primary amines not suitable for making a pure primary amine?

A

The product still contains a lone pair of electrons on the nitrogen atom that can react further with a haloalkane to form a secondary amine

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36
Q

primary amine + haloalkane —>

A

ammonium salt

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37
Q

CH₃CH₂CH₂Cl + CH₃CH₂CH₂NH₂ —>

A

(CH₃CH₂CH₂)₂NH⁺Cl⁻

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38
Q

How do you obtain a secondary amine from its salt?

A

By reacting the salt with sodium hydroxide

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39
Q

(CH₃CH₂CH₂)₂NH₃⁺Cl⁻ + NaOH —>

A

(CH₃CH₂CH₂)₂NH + NaCl +H₂O

40
Q

How do you form tertiary amines?

A

Further reaction of the secondary amine

41
Q

How do you form a secondary amine?

A

Further reaction of the primary amine

42
Q

How is phenylamine made?

A

By reducing nitrobenzene

1) nitrobenzene heated under reflux with tin + hydrochloric acid —> ammonium salt
2) ammonium salt reacted with excess sodium hydroxide —> aromatic amine + water

43
Q

What is an amino acid?

A

Organic compound containing both amine, NH₂, and carboxylic acid, COOH, functional groups

44
Q

How many common amino acids does the body have?

A

20

45
Q

What is an α-amino acid?

A

The amine group is attached to the α-carbon atom - the second carbon atom, next to the carboxyl group

46
Q

How do the 20 amino acids differ?

A

By the side chain, R, attached to the same alpha-carbon atom

47
Q

What is the general formula of an alpha-amino acid?

A

RCH(NH₂)COOH

48
Q

What is the β-carbon atom?

A

third carbon

49
Q

What is the γ-carbon atom?

A

fourth carbon

50
Q

What do amino acid react with acids to form?

A

salts

51
Q

What do carboxylic acids react with alkalis to form?

A

salts

52
Q

What do carboxylic acids react with alkalis to form?

A

esters

53
Q

What do amino acids react with alkalis to form?

A

salt + water

54
Q

What aqueous alkalis do amino acids react with?

A

1) sodium hydroxide

2) potassium hydroxide

55
Q

How are amino acids esterified?

A

By heating with an alcohol in the presence of concentrated sulfuric acid

56
Q

What is a zwitterion?

A

Amine group that accepts a proton from the carboxylic acid group to form an ion containing both a positive and negative charge

57
Q

What is the overall charge of a zwitterion?

A

Zwitterions have no overall charge

58
Q

Why do zwitterions have no overall charge?

A

The positive and negative charges cancel out

59
Q

What is the isoelectric point?

A

The pH at which the zwitterion is formed

60
Q

If an amino acid is added to a solution with a pH greater than its isoelectric point, what happens?

A

The amino acid behaves as an acid and loses a proton

61
Q

If an amino acid is added to a solution with a pH lower than its isoelectric point, what happens?

A

The amino acid behaves as a base and gains a proton

62
Q

What are amides?

A

The products of reactions of acyl chlorides with ammonia and amines

63
Q

Where are amide groups common?

A

In nature

64
Q

What are amides classified as?

A

1) primary
2) secondary
3) tertiary

65
Q

What is a primary amine?

A

One carbon atom bonded to N

66
Q

What is a secondary amine?

A

Two carbon atoms bonded to N

67
Q

What is a tertiary amine?

A

Three carbon atoms bonded to N

68
Q

What are stereoisomers?

A

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

69
Q

Where is optical isomerism found?

A

In molecules that contain a chiral centre

70
Q

What is the chiral centre?

A

A carbon atom that is attached to four different atoms or groups

71
Q

What does the presence of a chiral carbon atom mean?

A

The existence of two non-superimposable mirror image structures

72
Q

What are optical isomers/enantiomers?

A

two non-superimposable mirror image structures

73
Q

For each chiral carbon atom, how many pairs of optical isomers are there?

A

One

74
Q

How is a chiral carbon shown?

A

Labelled with an asterisk

75
Q

How are optical isomers drawn?

A

To show the 3D tetrahedral arrangement of 4 different groups around central chiral carbon atom

76
Q

How do alkenes form polymers?

A

Addition polymerisation

77
Q

What are the two important condensation polymers?

A

1) polyesters

2) polyamides

78
Q

What is condensation polymerisation?

A

The joining of monomers with loss of a small molecule, usually water/hydrogen chloride

79
Q

What can polyesters be made from?

A

1) 1 monomer - containing both carboxylic acid and alcohol groups
2) 2 monomers - 1 contaning 2 carboxylic acid groups, 1 containing 2 alcohol groups

80
Q

What are the monomers for the polyester formation where 2 monomers are involved?

A

1) diol

2) dicarboxylic acid

81
Q

What other acid can a polyester be made using?

A

diacyl chloride

82
Q

When a diacyl chloride is used to make a polyester, what is lost, instead of water?

A

hydrogen chloride

83
Q

What are polyamides

A

Condensation polymers formed when monomers are joined together by amide linkages in a long chain to form the polymer

84
Q

What can polyamides be made from?

A

1) 1 monomer - containing both carboxylic acid (or acyl chloride) and amine groups
2) 2 monomers - 1 containing 2 carboxylic acid (or acyl chloride) groups, 1 containing 2 amine groups

85
Q

What do amino acids undergo condensation polymerisation to form?

A

polypeptides/proteins

86
Q

What does a polypeptide/protein contain?

A

Many different amino acids all linked together by amide bonds

87
Q

What can polyesters + polyamides be hydrolysed using?

A

1) hot aqueous alkali (sodium hydroxide)

2) hot aqueous acid (hydrochloric acid)

88
Q

What shape are amines?

A

trigonal pyramidal

89
Q

What is the bond angle of amines?

A

107°

90
Q

What intermolecular forces do amines have?

A

1) hydrogen bonding
2) the N-H bond is polar
3) lone pair of electrons on the Nitrogen atom

91
Q

Are the intermolecular forces in amines stronger or weaker than alcohols?

A

Weaker because Nitrogen has a lower electronegativity value than Oxygen, which means the hydrogen bonding is weaker

92
Q

In order to be the strongest base, what must an amine have?

A

A greater electron density around the Nitrogen atom to make it a better electron pair donor

93
Q

What conditions are needed to form nitrobenzene from benzene?

A

1) concentrated sulfuric acid

2) nitric acid

94
Q

What is the equation for the production of phenylamine, C₆H₅NH₂ from nitrobenzene, C₆H₅NO₂?

A

C₆H₅NO₂ + 6[H] –> C₆H₅NH₂ + 2H₂O

95
Q

What is [H]?

A

reducing agent

Chemistry OCR A-Level (28 decks)

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