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Chemistry > Ch6.2 Nitrogen compounds, polymers and synthesis > Flashcards

Ch6.2 Nitrogen compounds, polymers and synthesis Flashcards

1
Q

What molecule are amines related to?

A

ammonia

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2
Q

What are amines essentially?

A

organic molecules in which one or more of the H atoms in ammonia have been replaced by an alkyl chain

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3
Q

What are primary amines?

A
  • only one H atom has been replaced by an alkyl chain
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4
Q

What are secondary amines?

A
  • 2 H atoms have been replaced by alkyl chains
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5
Q

What are tertiary amines?

A
  • all 3 H atoms have been replaced by alkyl chains
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6
Q

How are primary amines named?

A
  • the root is the longest carbon chain
  • the suffix is ‘amine’
  • any side groups are added alphabetically as prefixes
  • numbers for prefixes are determined by counting away from the N
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7
Q

How are secondary amines named?

A
  • name both alkyl chains
  • the longest chain is the root of the name
  • ‘amine’ is suffix
  • name side groups and add them as prefixes
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8
Q

How are tertiary amines named?

A
  • name all 3 alkyl chains
  • longest chain is the root
  • if there’s identical alkyl groups, use ‘di’ or ‘tri’
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9
Q

What can amines act as and why?

A
  • amines can act as bases (proton acceptors)
  • amines can act as nucleophiles (they can donate a lone pair of electrons to a region of positive charge)
  • amines can do both of these things due to the lone pair of electrons on the nitrogen atom
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10
Q

When amines react with acids as bases, what organic molecule is produced?

A
  • ammonium salt
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11
Q

How can amines be produced?

A
  • by reacting ammonia with haloalkanes
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12
Q

Describe the 2 stage reaction used to produce amines

A
  1. an ammonia molecule reacts with a haloalkane to make an ammonium salt
  2. a second ammonia molecule reacts with the ammonium salt produced in stage 1. This produces a primary amine and ammonium chloride

stage 2 is reversible

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13
Q

How is the equilibrium of the second stage of producing an amine driven to the product side?

A

add excess ammonia

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14
Q

Which 2 functional groups are amino acids guaranteed to have?

A
  • amine group
  • carboxylic acid group
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15
Q

What are polymers?

A
  • long-chain molecules made from smaller molecules (monomers) linked together
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16
Q

What are the 2 types of polymers?

A
  • addition: the monomers link together to make a single product
  • condensation: the monomers link together to make a polymer and one other product (usually water)
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17
Q

What must the monomers of addition polymers have?

A

C=C bond

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18
Q

What are the 2 types of condensation polymers?

A
  • polyesters
  • polyamides
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19
Q

What are the monomers of polyesters?

A
  • dicarboxylic acid
  • diol
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20
Q

What are the monomers of polyamides?

A
  • dicarboxylic acid
  • diamine
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21
Q

Give an example of a polyester

A

poly(lactic acid)

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22
Q

Give an example of a polyamide

A

nylon

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23
Q

What is the monomer and use of poly(ethene)?

A
  • ethene
  • carrier bags
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24
Q

What is the monomer and use of poly(chloroethene)? aka PVC

A
  • chloroethene
  • rulers, cling film, pipes, window frames
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25
Q

What is the monomer and use of poly(propene)?

A
  • propene
  • ropes, crates, storage boxes
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26
Q

What is the monomer and use of poly(ethylbenzene)? aka polystyrene

A
  • ethylbenzene
  • food packaging, cups
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27
Q

How are esters formed?

A
  • when an alcohol reacts with a carboxylic acid
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28
Q

What kind of reaction is simple esterificatio

A
  • reversible
  • condensation (water is eliminated)
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29
Q

How are esters named?

A
  • alcohol first (yl)
  • carboxylic acid last (oate)
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30
Q

How must you change the reactants for esterification to result in a polyester rather than an ester?

A
  • the monomers must be a diol and a dicarboxylic acid

(instead of an alcohol and a carboxylic acid)

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31
Q

How is poly(lactic acid) formed?

A
  • lactic acid is a natural monomer with both an alcohol group and a carboxylic acid group
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32
Q

What is the polymer of amino acid monomers?

A
  • proteins/polypeptides
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33
Q

When do amide linkages form?

A
  • when an amine group reacts with a carboxylic acid group
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34
Q

What are the monomers of a polyamide?

A
  • diamine
  • dicarboxylic acid
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35
Q

During polymerisation, when are 2n H2O molecules formed rather than just n?

A
  • when diamines, diols or dicarboxylic acids are used
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36
Q

How do proteins (formed from amino acids) and polyamides (formed from diamines and dicarboxylic acids) differ in their bonding?

A
  • in proteins, all amide links have the same orientation
  • ie. CONH, CONH, CONH
  • in polyamides, amide links have alternating orientations
  • ie. CONH, NHCO, CONH, NHCO
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37
Q

Describe ethene polymerisation

A

1- initiation.
H-O-O-H –> 2 ‘O-H (radicals)
(using UV light)

2- propagation.
H-O’ + C2H4 –> CH2OHCH2’

CH2OHCH2’ + C2H4 –> CH2OHCH2CH2CH2’

and so on…

3- termination.
CH2OHCH2’ + CH2OHCH2’ –> CH2OHCH2CH2CH2OH

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38
Q

What is a nylon?

A
  • a polyamide in which the monomers are straight chain
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39
Q

How are nylons named?

A
  • nylons are named uniquely
  • eg. Nylon- 3,4 is made of a diamine with 3 carbons and a dicarboxylic acid with 4 carbons
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40
Q

How are aliphatic amines formed?

A
  • heating a haloalkane and excess ammonia in ethanol (solvent)
  • this is done in a sealed container and not under reflux as ammonia is very volatile
  • this prep method will always produce a mixture of primary, secondary, tertiary and quaternary ammonium salts
41
Q

What type of reaction is the reaction between excess ammonia and haloalkanes to form aliphatic amines?

A
  • nucleophilic substitution
42
Q

How is production of the primary amine favoured in the production of aliphatic amines?

A
  • add excess ammonia
43
Q

How are aromatic amines produced?

A
  • by the reduction of nitroarenes
44
Q

What is the reducing agent for producing aromatic amines from nitroarenes?

A
  • it’s formed in situ using tin (source of electrons) and conc HCl under reflux at 100 degrees C
45
Q

What are the 2 stages of reaction for forming aromatic amines from nitroarenes?

A
  • the reaction initially forms the phnylammonium salt
  • this salt is then reacted with sodium hydroxide to remove the hydrogen ion and excess HCl
46
Q

After the reaction for the production of aromatic amines from nitroarenes, how is the amine separated?

A
  • steam distillation
  • solvent extraction
  • more distillation
47
Q

Why are amino acids amphoteric?

A
  • they have an acidic carboxyl group and a basic amine group
48
Q

What are the 2 types of stereoisomers?

A
  • optical isomers
  • E/Z isomers
49
Q

What is optical isomerism?

A
  • when 2 molecules are chemically identical but they cannot be super-imposed on top of one another
  • they’re mirror images
  • they react with polarised light differently
50
Q

What properties are similar and different in enantiomers?

A
  • similar physical properties
  • same chemical properties
  • different biological properties
51
Q

What is an example of a pair of enantiomers that have different biological properties?

A
  • limonene
  • a chiral hydrocarbon found in citrus fruit
  • one enantiomer smells strongly of oranges
  • the other enantiomer smells of pine
52
Q

What do the prefixes of + and - mean on enantiomers?

A
  • this is the effect the enantiomer has on a plane of polarised light
  • if the enantiomer rotates the plane of polarised light clockwise then its prefix is +
  • if it rotates the plane of polarised light anti-clockwise then its prefix is -
  • prefixes can only be deduced by experiment, not from the structures
53
Q

What is a 50:50 mixture of enantiomers known as?

A
  • a racemate
  • or a racemic mixture
54
Q

What effect will a racemic mixture have on polarised light?

A
  • no effect
  • the rotations of the two isomers cancel each other out
55
Q

What is the condition for optical isomers to be formed?

A
  • the molecule must have a chiral centre
56
Q

What is a chiral carbon or a chiral centre?

A
  • a carbon atom with 4 different groups attached
57
Q

What is hydrolysis?

A
  • hydrolysis is the chemical reaction in which water breaks bonds
58
Q

What is produced during hydrolysis of condensation polymers?

A
  • the monomers
59
Q

Why do condensation polymers, eg. nylon, not degrade when it rains?

A
  • hydrolysis of polyesters and polyamides has a very slow rate of reaction
60
Q

How can you hydrolyse condensation polymers faster than just using water?

A
  • in acidic or basic conditions
  • the rate can be increased even further by heating the reaction mixture
61
Q

Is acidic or basic hydrolysis of polyesters faster?

A
  • basic hydrolysis of polyesters is much faster
  • acidic hydrolysis has a slow rate of reaction
62
Q

Describe the process of acidic hydrolysis of polyesters?

A
  • polyester reacted with strong aqueous acid
  • reaction produces a diol and a dicarboxylic acid

SLOW RATE OF REACTION

63
Q

Describe the process of alkali hydrolysis of polyesters

A
  • polyester reacted with hot NaOH solution
  • produces diol and salt of the carboxylic acid

FAST RATE OF REACTION

64
Q

Is acidic or basic hydrolysis of polyamides faster?

A
  • acid hydrolysis of polyamides is much faster
65
Q

Describe the process of acid hydrolysis of polyamides

A
  • polyamide reacted with strong aqueous acid
  • produces a diammonium salt and a dicarboxylic acid
66
Q

Describe the process of alkali hydrolysis of polyamides

A
  • polyamide is reacted with hot NaOH solution
  • produces the diamine and the salt of the dicarboxylic acid
67
Q

What is the difference between cyanide and nitrile?

A
  • CN- ion is known as the cyanide ion
  • when the CN group is found in an organic chemical it becomes known as a nitrile functional group
68
Q

Is cyanide a nucleophile or an electrophile?

A
  • nucleophile
  • attracted to areas of positive charge in a molecule
69
Q

Which organic molecules are susceptible to attack by nucleophilic attack of a cyanide ion and why?

A
  • haloalkanes
  • C-X bond has a dipole due to difference in electronegativity between carbon and halogen
70
Q

What conditions and reagents are needed for nucleophilic substitution of a cyanide ion on a haloalkane?

A
  • haloalkane mixed with potassium cyanide
  • heated under reflux
  • ethanol used as a solvent to ensure the nucleophile is the cyanide ion
71
Q

Why is ethanol used as the solvent for extending carbon chain length using cyanide ions on haloalkanes and not water?

A
  • ethanol as a solvent ensures the nucleophile is the cyanide ion
  • if water is used, the hydroxide ion tends to be the nucleophile and the carbon chain length would not increase
72
Q

What is the mechanism for extending the carbon chain length using cyanide ions and haloalkanes?

A

nucleophilic substitution

  • cyanide takes the place of the halogen
73
Q

Other than haloalkanes, what kind of organic molecules are susceptible to nucleophilic attack?

A
  • carbonyls
  • in C=O bond, the carbon has a slight positive charge which nucleophiles can attack
74
Q

How does cyanide react with carbonyls?

A
  • hydrogen cyanide is used to generate the cyanide nucleophile
  • cyanide ion is attracted to the carbon of the carbonyl group and forms new covalent bond
75
Q

What does cyanide + carbonyl result in and why?

A
  • hydroxynitrile
  • the pi bond of the C=O opens and the oxygen accepts the pair of electrons
  • oxygen is then negatively charged and so accepts a proton and becomes an OH group
76
Q

How does cyanide + (some) carbonyls result in a racemic mixture?

A
  • the C=O bond is planar
  • equal chance of which side the nucleophile may attack from
77
Q

Which carbonyls will produce a racemic mixture when reacted with cyanide?

A
  • asymmetric ketones
  • any aldehyde other than methanal
78
Q

In labs, is HCN or KCN more commonly used and why?

A
  • HCN is a highly toxic gas in normal lab conditions
  • KCN is a cyanide salt and is much safer in labs
  • KCN is solid at room temp and is easier to handle
79
Q

How must KCN be used if it is used for the reaction of extending carbon chain length?

A
  • the salt must be in an acidified solution so both CN- and H+ ions are present
80
Q

What is formed when nitriles are reduced?

A
  • amines
81
Q

Can hydrogen gas react directly with a nitrile and if so what happens?

A
  • hydrogen gas can react directly with a nitrile to form a primary aliphatic amine in the presence of a nickel catalyst
  • 2 hydrogen atoms are added to the nitrogen atom of the nitrile group
82
Q

Does the reduction of a nitrile require a catalyst?

A
  • yes
  • nickel catalyst
83
Q

How is the rate of reaction increased when reducing nitriles?

A
  • nickel catalyst lowers activation energy to enable reaction to occur
  • mixture is heated to 150 degrees C at raised pressure
84
Q

What are the conditions and reagents for typical reduction of nitriles?

A
  • nickel catalyst
  • 150 degrees C
  • raised pressure
  • H2
85
Q

What is an alternative method of reducing nitriles other than using hydrogen gas?

A
  • using a reducing agent such as lithium tetrahydridoaluminate(III), LiAlH4
85
Q

What is formed when nitriles are hydrolysed?

A
  • initially forms an amide
  • then forms an ammonium salt
  • second reaction to form an ammonium salt is so slow that it isn’t significant
86
Q

How can the rate of reaction for the hydrolysis of nitriles be increased?

A
  • strong acid catalyst
  • heat under reflux
87
Q

How does normal hydrolysis and acid hydrolysis of nitriles differ?

A
  • normal hydrolysis produces an amide and then an ammonium salt (slow)
  • acid hydrolysis produces carboxylic acids
88
Q

If a nitrile undergoes acid hydrolysis, a carboxylic acid and an ammonium salt are formed. Why is an organic acid formed and not an organic ammonnium salt?

A
  • the strong acid ionises fully in solution forming H+ and Cl- ions
  • when the amide has formed, the C-N bond breaks, making a carboxylate ion
  • carboxylate ion reacts with proton from the strong acid to make a carboxylic acid
  • organic acids are weak and would only partially ionise in solution
89
Q

What is the mechanisms for substitution reactions of arenes and how are these reactions facilitated?

A
  • electrophilic substitution
  • catalyst needed such as AlCl3 or FeCl3
90
Q

What are the 2 types of substitution reaction in aromatic compounds?

A
  • alkylation
  • acylation
91
Q

What are the reagents for alkylation of an aromatic compound?

A
  • an aromatic compound
  • haloalkane
  • strong Lewis acid catalyst
92
Q

What are the conditions for benzene reacting with chloromethane and what organic compound is produced?

A
  • FeCl3 catalyst needed
  • methylbenzene produced
93
Q

What is the mechanism for alkylation of an aromatic compound?

A
  • electrophilic substitution
94
Q

What occurs during acylation?

A
  • RCO- is added to an organic compound (R is a hydrocarbon chain)
95
Q

What are the reagents and conditions for acylation of an organic compound?

A
  • an acyl chloride
  • a strong Lewis acid catalyst
  • heat under reflux
96
Q

How do benzene and ethanoyl chloride react?

A
  • heated under reflux
  • acylation
  • anhydrous AlCl3
  • electrophilic substitution
97
Q

What is the mechanism for acylation of an organic compound?

A
  • electrophilic substitution

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