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Chemistry > Production of Materials - POLYMERS > Flashcards

Production of Materials - POLYMERS Flashcards

1
Q

Functional groups

A

The group of atoms that determine the properties of the compound

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2
Q

Homologous series

A

A ‘family’ of chemicals that all have the same functional group e.g. alkanes, alkanols

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3
Q

Alkyl

A

Addition of alkane minus 1 H

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4
Q

Alkanol

A

Addition of hydroxyl group

  • primary alkanol: -OH is terminal [end of C chain] therefore the C-OH is only attached to one other C atom
  • secondary alkanol: the C-OH is attached to 2 other C atoms
  • tertiary alkanol: the C-OH is attached to 3 other C atoms
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5
Q

Alkanoic Acid

A

Addition of carboxylic acid group

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6
Q

Haloalkane

A

Addition of halogen

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7
Q

Alkanone [ketone]

A

Addition of oxygen

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8
Q

Alkanal [aldehyde]

A

addition of oxygen and hydrogen [separately]

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9
Q

Alkyl alkanoate [ester]

A

y is named first [alkyl]

x is followed by ‘oate’

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10
Q

Alkanoxyalkane [ether]

A
  • oxygen is in the middle of two alkyls [oxy]
  • shortest alkyl group named first
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11
Q

Aminoalkane [amine]

A

Addition of amino group [-NH2]

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12
Q

Alkyl alkanamide [amide]

A
  • y named first [alkyl]
  • x followed by ‘amide’
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13
Q

Ethene Production

A
  • dehydrating ethanol using a concentrated catalyst H2SO4 [formula seen in image below]
  • cracking of fractions produced in the refining process of crude oil
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14
Q

Cracking

A

decomposition involving the breakdown of organic molecules

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15
Q

Hydrocarbon cracking

A

Steam/thermal cracking [pyrolysis occurs at high temperatures of 700-900oC]

  • non-catalytic
  • mixtures of alkanes are passed through very hot metal tubes with steam to decompose into smaller alkenes
  • e.g. ethane → ethene

Catalytic Cracking

  • heavy crude oil is heated in the presense of a zeolite [Al silicate]
  • catalyst allows allows cracking to occur at lower temperature [approx. 500oC]
  • this process is carried out because of the high demand for short chain molecules e.g. ethene in petrochemical indutry
  • example equation:
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16
Q

Hydrocarbon Safety Issues [C1 - C4]

A

C1 - C4:

  • highly flammable [high autoignition temp therefore will not spontaneously ignite]
  • volatile gases [low flash point] therefore must be stored in high pressure cylinders
  • these cylinders must be checked for leaks regularly
  • simple asphyxiants - can cause death as a result of lack of oxygen
  • mild anaesthetics [except methane]
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17
Q

Hydrocarbon Safety Issues [liquid hydrocarbons]

A
  • volatile [vapourise readily] therefore stored in heavy metal containers
  • containers stored in well ventilated areas
  • low flash point therefore never handled near naked flames
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18
Q

Hydrocarbon Safety Issues [benzene]

A
  • volatile liquid
  • flammable
  • carcinogen
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19
Q

Hydrocarbon Safety Issues [C5 - C8]

A
  • can cause skin and eye irritation and narcosis [drowsiness or unconsciousness]
  • hexane also causes neuropathy therefore used in fume cupboard and with breating apparatus
20
Q

Combustion of ethene

A

C2H4 (g) + 3O2 (g) → 2CO2 (g) + 2H2O(g)

21
Q

Combustion of ethanol

A

Complete:

C2H5OH(l) + 3O2 (g) → 2CO2 (g) + 3H2O(g)

Incomplete:

2C2H5OH(l) + 5O2 (g) → 2CO2 (g) + 2CO(g) + 6H2O(g)

22
Q

Ethene

A
  • highly reactive across double bond
  • unsaturated
  • oily nature [alkene]
  • volatile gas therefore low b.p. and m.p.
  • flammable therefore good fuel
23
Q

Reactions of Alkenes [mainly ethene]

A
  • combustion
  • hydration
  • hydrogenation
  • halogenation
  • hydrohalogenation
  • oxidation
  • polymerisation
24
Q

Combustion of alkenes

A
  • addition of O2 (g)
  • burning [oxidation]
  • fuel + O2 → CO2 + H2O + energy
    • this is assuming complete combustion [plenty of O2]
25
Q

Hydration of alkenes

A
  • addition of H2O
  • often used to produce ethanol from ethene
  • requires acid catalyst [usually dilute H2SO4 solution]
  • used in industry to produce alcohols, cosmetics and medicines
    • to maximise yield, ethene is reacted with water at high temp. [approx 300°C] and high pressure and use phosphoric acid [H3PO4] as catalyst
    • ethanol is a fuel additive and used in thermometers
26
Q

Hydrogenation of alkenes

A
  • addition of H2 (g)
  • requires a metal catalyst [usually Pt or Ni - do not take part in the reaction} - this catalyst is heated to 150°C
  • the basis for producing margarine
    • from vegetable oils [from double to single bonds - saturates]
    • this causes oils to harden into soft solids
27
Q

Halogenation of alkenes

A
  • the addition of halogen
  • no need for catalyst as both alkene and halogen are reactive
  • example - 1,2 - dichloroethane [refrigerant and aerosol propellant]
28
Q

Hydrohalogenation of alkenes

A
  • addition of hydrogen and halogen
  • examples:
    • HF [strongest acid] → flouroalkane
    • HCl → chloroalkane
    • HBr → bromoalkane
  • bromoethane is an industrial solvent
29
Q

Oxidation of alkenes

A
  • addition of potassium permanganate [KMnO4 (aq)]
    • very strong oxidising agent and very reactive
  • oxidation of ethene equation is as follows:
30
Q

Polymerisation of alkenes

A
  • making polymers [plastics]
  • polymer: a long chain molecule made up of repeating units [monomers]
  • ethene is the starting point for many polymers
31
Q

Addition Polymerisation

A
  • initiation:
    • requires a catalyst [organic peroxide] to break the double bond in the monomer
    • forms free radicals [highly reactive due to the unpaired electrons]
  • propogation:
    • monomers attach to carbon chain at free radicals
  • termination:
    • no more monomers can be added to polymer chain
    • formation of polymer
32
Q

Initiation of ethene

A

shown with the following structural equation:

33
Q

Propogation of ethene free radicals

A

shown with the following structural equation:

34
Q

Termination of ethene

A

the final polymer product is shown as:

35
Q

Polyethene [polyethylene]

A
  • can be low or high density PE
  • produced using addition polymerisation
36
Q

LDPE

A
  • low density polyethylene
  • still use I.P.T. process
  • catalyst - organic peroxide
  • conditions:
    • 100-300°C
    • very high pressure [1500-3000 atmosphere]
    • this decreases volume and increases collision frequency of free radicals thereby increasing the yield of polymer
  • structure:
    • tends to have shorter polymer chains with lots of side branches [up to 5 C atoms]
    • side branches prevent close packing of chains therefore low density
  • same formula = [C2H4]n
  • properties:
    • tough
    • brittle
    • flexible
    • semi-crystalline [lots of spacing and low density areas]
    • transparent/transluscent
    • very pure compound
    • not heat resistant
  • uses:
    • gladwrap
    • plastic bags
    • tupperware
37
Q

HDPE

A
  • high density polyethylene
  • still use I.P.T.
  • catalyst - zeigler-natta [Al based oxide]
  • conditions:
    • optimum is 300°C
    • low pressure [1-2 atmosphere]
  • structure:
    • long, linear chains with very few or no side chains therefore when cooled, the molecules pack closer together therefore high density
  • same formula - [C2H4]n
  • properties:
    • very strong
    • less flexible
    • less transparent [often appears white]
    • does contain some impuities [zeigler-natta partially breaks down]
    • heat resistant [>100°C]
  • uses:
    • oven bags
    • kitchen electrical appliances
    • water pipes
    • buckets
    • wheelie bins
    • petrol tanks
38
Q

Polyvinyl chloride [PVC]

A
  • monomer: chloroethene [vinyl chloride]
  • undergoes addition polymerisation
39
Q

Polystyrene

A
  • monomer: ethenylbenzene [styrene]
  • undergoes addition polymerisation
40
Q

Polytetraflouroethene [teflon]

A
  • monomer: tetrafloroethene
  • undergoes addition polymerisation
  • polymer has an almost frictionless surface
    • used in non-stick fry pans, greaseless bearings etc.
41
Q

Condensation Polymerisation

A
  • usually requires two separate monomers
  • a condensation polymer forms by the elimination of a small molecule [usually H2O] when pairs of monomer molecules join together
  • cellulose is a naturally occurring condensation polymer which is formed from the monomer unit glucose
42
Q

Glucose

A
  • C6H12O6
  • carbohydrate in which the atoms are arranged in a ring [arranged as seen in image]
  • the presence of five hydroxyl groups allows the polymerisation of glucose to form cellulose, starch and glycogen
  • the ‘backbone’ of polymers is formed by the elimination of water [H2O] between C1 of one glucose molecule and C4 of another
43
Q

Cellulose

A
  • monomer: glucose [C6H12O6] - ring carbohydrate
  • undegoes condensation polymerisation
  • the elimination of water occurs between C1 of one glucose molecule and C4 of another
  • polymer contains 1800-3000 glucose units per molecule
  • fibre-like material - present as long chains packed close together
  • the polymer chains of cellulose lie parallel to the axis of the cellulose fibre
  • fibres are held together by strong H bonds [between H and OH groups
  • cotton fibres are 90% cellulose
  • rigid, strong, able to resist chemical attack and highly insoluble
44
Q

Starch

A
  • monomer: glucose [C6H12O6] - ring carbohydrate
  • undergoes condensation polymerisation
  • the elimination of water occurs between C1 of one glucose molecule and C4 of another
  • fluffy, powdery material with numerous side chains
  • isn’t as closely packed as cellulose
  • not very reactive [insoluble in cold water but soluble in hot water]
45
Q

Natural vs Synthetic

A

Natural:

  • starch
  • cellulose
  • rubber
  • cotton
  • silk

Synthetic:

  • made from fossil fuels
  • polyethylene [PE]
  • polyvinylchloride [PVC]
  • polystyrene [PS]
  • Teflon
  • Kevlar
  • nylon
46
Q

Fermentation of glucose

A
  • decomposition process of glucose into ethanol
  • chemical equation for fermentation: C6H12O6 (aq) → 2C2H5OH(l) + 2CO2 (g)
  • conditions necessary:
    • the substrate [glucose or succrose] being in solution
    • the presence of yeast [provides catalyst zymase]
    • an approx. temperature of 37°C [blood temp.]
    • the exclusion of air [anaerobic]
    • suitable pH
    • N.B. once the cocentration of ethanol reaches 14-15% the yeast can no longer survive therefore fermentation stops
47
Q

Biopolymers

A

Chemistry (2 decks)

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