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A-Level Organic Chemistry AQA (Paper 2) > Polymerisation > Flashcards

Polymerisation Flashcards

1
Q

What is a polymer?

A

•Long chain molecule made from lots of small molecules (repeating units) joined together.

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2
Q

What is a monomer?

A

•Small molecules that join together to make polymers.

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3
Q

What are the two types of polymers?

A

•Addition and condensation.

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4
Q

What are addition polymers? (2)

A
  • Formation of long chain molecules from lots of small molecules joining together with no other products.
  • All have a double bond - free radical mechanism, double bond breaks and monomers join together.
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5
Q

What are condensation polymers? (2)

A
  • Formation of long chain molecules from lots of small molecules together with another small molecule (e.g. water) produced as well.
  • Polyamides (amide) or polyester (ester linkage).
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6
Q

How do you draw a monomer?

A

•Around the double bond.

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7
Q

What is a condensation reaction?

A

•When two molecules react together and a small molecule e.g. water or hydrogen chloride is eliminated.

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8
Q

Describe the condensation reaction of the formation of esters. (2)

A
  • When carboxylic acids and alcohols react together.

* Water is eliminated, hydrogen from the alcohol and an -OH group from the carboxylic acid.

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9
Q

What are condensation polymers normally made up of? (2)

A
  • Two different monomers, each with two functional groups.

* Both functional groups can react, forming long-chain polymers.

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10
Q

Give some examples of condensation polymers. (3)

A
  • Polyesters.
  • Polyamides.
  • Polypeptides.
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11
Q

What are polyesters?

A

•They have the ester linkage -COO- repeated over and over again.

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12
Q

How are polyesters formed? (3)

A
  • Using diols - they have two -OH groups, and dicarboxylic acids, which have two carboxylic acid groups -COOH.
  • The functional groups of each ends of a diols and dicarboxylic acids react together to form a chain by eliminating molecules of water.
  • -OH from dicarboxylic acid and H from diol.
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13
Q

What are polyamides?

A

•They have the amide linkage -CONH- repeated over and over again.

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14
Q

How are polyamides formed?

A

•When dicarboxylic acids and diaminoalkanes react together in a condensation reaction, -OH from dicarboxylic acid and H from diamine.

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15
Q

What are the two common condensation polymers?

A

•Nylon and Kevlar.

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16
Q

How is nylon-6,6 made industrially?

A

•Condensation reaction of 1,6-diaminohexane and hexane-1,6-dicarboxylic acid.

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17
Q

How is nylon-6,10 made in the lab? (3)

A
  • When a diacid chloride is used instead of a dicarboxylic acid - hydrogen chloride is eliminated.
  • Nylon-6,10 made from 1,6-diaminohexane and decane-1,10-dicarboxylic acid.
  • Many other nylons are made each with slightly different properties.
18
Q

How is kevlar made? (2)

A
  • From benzene-1,4-diamine and benzene-1,4-dicarboxylic acid.
  • Amide groups are linking rigid benzene rings, making kevlar have different properties to nylon.
19
Q

Why is kevlar strong?

A

•Due to the rigid chains and the ability of the flat aromatic rings to pack together held by strong intermolecular forces.

20
Q

What is kevlar used for? (2)

A
  • Bulletproof vests and anti-stab clothing worn by police.

* Oven and gardening gloves.

21
Q

What are polypeptides?

A

•Polyamides made from a single amino acid monomer, or many different ones.

22
Q

What does a polypeptide consist of and its formation? (3)

A
  • Each amino acid has both an amine group and a carboxylic group.
  • The amine group of one amino acid can react with the carboxylic acid group of another to form an amide (peptide) linkage.
  • One molecule of water is eliminated and a condensation polymer can be formed.
23
Q

What are the differences between a polymer like nylon-6,6 and a polypeptide? (2)

A
  • Nylon-6,6 - two monomers (one diamine, H2N-X-NH2 and one a dicarboxylic acid, HOOC-Y-COOH).
  • Polypeptide - each amino acid monomer has one NH2 group and one -COOH group (H2NCHRCOOH).
24
Q

How many naturally occurring varieties of amino acids are there?

A

•20 amino acids.

25
Q

How do you identify the repeat unit of a condensation polymer?

A

•By starting at any point in the polymer and stopping when the same pattern of atoms begins again.

26
Q

How do you identify the monomer(s) of a condensation polymer? (4)

A
  • Try and recognise the links formed by familiar functional groups.
  • 1). Start with the repeat unit.
  • 2). Break the linkage (at the C-O for a polyester or C-N for a polyamide).
  • 3). Add back the components of water for each ester of amide linkage.
27
Q

Which polymers are not biodegradable?

A

•Polyalkanes and polesters.

28
Q

Which polymers are biodegradable?

A

•Polyamides - they can be hydrolysed.

29
Q

Why are poly(alkenes) such as poly(ethene) and poly(propene) not biodegradable? (3)

A
  • They are long-chain alkane molecules.
  • Alkanes are unreactive because they only have strong, non-polar C-H and C-C bonds.
  • There is nothing natural in the environment that will easily break them down and they persist for many years.
30
Q

How are polymers disposed of? (2)

A
  • In landfill sites, along with other rubbish or by incineration.
  • Some may be melted down and remoulded.
31
Q

What are the advantages of incineration of polymers? (2)

A
  • Poly(alkenes) can be burnt to carbon dioxide and water to produce energy at high temperatures in a furnace - heat energy can generate electricity.
  • Reduces the need for landfills.
32
Q

What are the disadvantages of incineration of polymers? (5)

A

•Poisonous carbon monoxide may be released into the atmosphere if combustion is incomplete (when there is a shortage of oxygen):
-[-CH2-]-n + 1 1/2nO2 —> nCO2 + nH2O
•Removing toxic gases e.g. NOx and chlorine adds to the cost.
•Unburnt carbon particulates (soot):
•Under certain conditions, the polymer may depolarise to produce toxic styrene vapour.

33
Q

What is an advantage of landfill disposal of polymers?

A

•Cheap and easy to deposit the waste.

34
Q

What are the disadvantages of landfill disposal of polymers? (3)

A
  • Nuisance to local people - attracts animals and bad smells.
  • Fuel cost to transport the waste to sites.
  • Costs to treat the waste before disposal.
35
Q

How can polyester materials be recycled? (3)

A
  • By being collected, sorted and then melted and reformed.
  • Fleece garments may be made from recycled soft drink bottles.
  • Costs and benefits must be balanced - melting and reforming of plastics can only be done a limited number of times, during the process the polymer chains tend to break and shorten, degrading the properties of the polymer.
36
Q

What are the advantages of recycling polymers? (2)

A
  • Almost all plastics are derived from crude oil - saves the expensive and diminishing resource, as well as the energy used in refining it.
  • Reduces polymers in landfill sites.
37
Q

What are the disadvantages of recycling polymers?

A

•Plastics need to be collected, transported and sorted, which uses energy and manpower = expensive.

38
Q

Why are condensation polymers like polyesters and polyamides biodegradable?

A

•They can be broken down by hydrolysis reactions, addition of a H2O molecule (opposite of a condensation reaction).

39
Q

Outline alternative methods for biodegradability in plastics. (6)

A
  • 1). Addition of a metal salt (transition metal) e.g. Mn, Fe, Co, Ni (heavy metal salts are poisonous).
  • Metal salt act as a catalyst for breaking down c-c bonds.
  • Plastic will become brittle and break down into small flakes and then they can be broken down by microorganisms.
  • 2). Producing plastics from natural resources (plant-based) e.g. corn starch or sugar cane by adding additives to produce the cyclic lactide monomer for polylactide.
  • 3). Poly(ethenyl ethanoate) reacted with methanol to remove the ester groups.
  • 4). Poly(ethenol) used to make plastic bags which dissolve in water e.g. in hospital laundry bags which avoids contact with the contents which may be infected.
40
Q

How are polyesters and polyamides broken down by hydrolysis? (5)

A
  • Reactivity is due to weak polar bonds in the polymer chain.
  • Nucleophiles e.g. H2O can break down the polyester or polyamide chains.
  • Hydrolysis reaction can be achieved in either base (OH-) or acid (H+).
  • Acidic hydrolysis produces the original monomers.
  • Basic hydrolysis produces the salt of the dicarboxylic acid monomer.
41
Q

Explain why the aqueous sodium hydroxide reacted with the polyester to make holes in the sleeve of a top.

A

•Polyester has delta positive carbon/electron deficient carbon which reacts with the hydroxide ion in base hydrolysis/saponification.

A-Level Organic Chemistry AQA (Paper 2) (17 decks)

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