PRODUCTION OF MATERIALS SAMPLE

Discuss the need for alternative sources of the compounds presently obtained from the
petrochemical industry
- Discuss = identify issues and provide points for and/or against
- The petrochemical industry is an industry that produces or uses compounds which come
from petroleum e.g. the production of fossil fuels and polymers.
- Some compounds presently obtained from the petrochemical industry include: petrol,
diesel, ethylene, polyethylene, kerosene, lubricating oils etc.
- Crude oil is the current source of fuels and petrochemicals e.g. plastic.
- The arguments FOR the need for alternative sources of petrochemicals include:
 The petroleum industry is based on the use of fossil fuels which are nonrenewable and likely to run out in the next few decades due to increasing
demand. If we can’t produce some of these petrochemicals, it would have a
devastating impact on our lives. Consequently, it is important that we look for
alternative sources of petrochemicals.
 There is also a need to find alternative sources of fuel, since the current use of
crude oil is environmentally damaging and causes large emissions of
greenhouse gases, contributing to global warming.
 Many of the polymers produced by the petrochemical industry from crude oil
are NOT biodegradable which can create pollution problems.
- The arguments AGAINST the need for alternative sources include:
 As oil supplies diminish, the cost of oil will increase and it will become too
expensive to use as a fuel. People will then look for alternative fuels. The
petrochemical industry won’t be affected by the price rises because the cost of
raw materials is a very small proportion of the cost of finished products. The oil
will become the exclusive domain of the petrochemical industry and will last for
many more decades.
 Alternative sources are currently uneconomical and until they become
financially feasible cannot effectively replace crude oil.
- The CONCLUDING JUDGEMENT is as follows:
 Regardless of which theory is correct, fossil fuels will run out sooner and later,
so there is a HUGE need to look for alternative sources e.g. ethanol and
cellulose to ensure intergenerational equity.
TALENT TIP: When answering this question, make as many points for both sides of the argument before
coming to a concluding judgement. Make sure you refer in detail to the need for alternative sources of
compounds and how they are presently obtained from crude oil. This shows a depth of understanding by
drawing on your knowledge of fractional distillation and cracking.

Explain what is meant by a condensation polymer
- Explain = relate cause and effect; make the relationships between things evident;
provide why and/or how
- Condensation polymers are polymers that form by the elimination of a small molecule
(e.g. H2O) when pairs of monomer molecules join together. Unlike addition
polymerisation, not all the atoms of the monomers are found in the final polymer. The
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reaction usually involves two different monomers, but can occur where a molecule
contains 2 different functional groups e.g. amino acids.
Cellulose is a naturally occurring condensation polymer. The monomer from which it
forms is beta glucose. To illustrate polymerisation let us write beta glucose, C6H12O6, as
HO-C6H10O4-OH. The polymerisation occurs by the elimination of water molecules from
between pairs of beta glucose molecules:
 HO-C6H10O4-OH HO-C6H10O4-OH HO-C6H10O4-OH HO-C6H10O4-OH
 The elimination of water molecules leaves us with:
 O-C6H10O4-O-C6H10O4-O-C6H10O4-O-C6H10O4-+xH2O
This is saying that n molecules of beta glucose combine to form one molecule of
cellulose (containing n glucose units) by eliminating (n-1) molecules of water.
Diagram:
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A synthetic condensation polymer is nylon-6. This is a particular type of nylon formed
from the monomer 6-aminohexanoic acid which has the structure:
 H2N-CH2-CH2-CH2-CH2-CH2-COOH
This can be written as H2N-(CH2)5-COOH. This molecule contains two functional groups,
the amine group – NH2 and the carboxylic acid group – COOH. Although written in these
ways for convenience, their full structures are:
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Carboxylic acids react with amines:
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Where Ra and Rb are the rest of the molecules (commonly alkyl groups). For convenience
this reaction is often written as:
 Ra-COOH + H2N-Rb  Ra-CO-NH-Rb + H2O
Molecules of a 6-aminohexanoic acid having both functional groups can react with one
another to form the polymer nylon-6. The polymerisation reaction is:
 H 2N-(CH2)5-COOH H 2N-(CH2)5-COOH H 2N-(CH2)5-COOH
 This leaves us with:
 -HN-(CH2)5-CO-HN-(CH2)5-CO-HN-(CH2)5-CO- +xH2O
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The chemical bond that has formed here is the same as occurs when proteins form: a
carboxylic acid group combines with an amine group to form an amide (peptide) link
(CO – NH). The generic name for nylon is polyamide.
Proteins are condensation polymers made from amino acids. Amino acids are
compounds with a –COOH group at one end and a –NH2 group at the other.
 Amino acids  protein + water
Describe the reaction involved when a condensation polymer is formed
- Describe = provides characteristics and features
- Condensation polymers are polymers that form by the elimination of a small molecule
(often water) when pairs of monomer molecules join together.
- Description (Dot Point): small monomer molecules each release one or more atoms and
the molecules join at that point. The released atoms combine to form a new compound.
For example, in the formation of cellulose, an H and an OH, released from adjoining
monomers, combine to form a molecule of water.
Comparing addition and condensation polymerisation
Similarities
Polymerisation definition – both reactions involve small monomers joining together to
form one long polymer chain (macromolecule)
Differences
AP (initiator/catalyst) CP (no general catalyst)
AP (monomers identical e.g. polyethylene + equation) CP (identical e.g. nylon
6-aminohexanoic acid OR different e.g. polyester, ethylene glycol)
AP (no other product) CP (small molecule e.g. H2O or NH3)
AP (double/triple bonds) CP (functional groups)
Sources of monomers AP (cracking petroleum) CP (degradation of polymers of b
biological origins e.g. cellulose or industrially synthesised)
Monomers/polymers/reactions (provide equations for polyethylene and
Cellulose)
Uses (for cellulose: major component of biomass, making ethanol etc.)
If a question asks you: compare addition polymers and condensation polymers (8 marks), define each
(2m), give one example of each e.g. cellulose/polyethylene (2m), give reactions of how each example is
produced (2m), different uses of the two examples (2m) (JRAHS 2006)
Condensation reactions
Addition reactions
Both involve monomers joining to form a long chain molecule
No double bonds necessary
Monomer has double bond which breaks
during polymerisation
Polymer forms and also a small molecule is
No small molecule produced
ejected e.g. water

Describe the structure of cellulose and identify it as an example of a condensation polymer
found as a major component of biomass
- Describe = provides characteristics and features
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Identify = recognise and name
Cellulose is a polymer of which the monomer units are beta glucose which are written as
HO-(C6H10O4)-OH. The structural formula (3D depiction) for glucose is:
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Glucose has 5 carbon atoms and an oxygen atom forming a puckered ring; there are OH
and H groups protruding above and below the C atoms. It also has a CH2 group out of the
ring. In solution the ring can open, forming a straight chain. The side of the ring (top or
bottom) on which each OH group is located is important. If you interchange an OH and H
on one of the C atoms, you get a different compound e.g. galactose or mannose. The 3D
structure can be abbreviated into:
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Cellulose is a very long polymer containing 2000-8000 beta glucose monomers. These
glucose molecules are strongly linked together by β -1, 4 glycosidic bonds. Hydrogen
bonding between the chains makes cellulose linear, strong and resistant to chemical
attack. When glucose molecules combine to form cellulose, the OH on the right hand C
atom of one molecule combines with the OH of the left-hand carbon atom of the next
glucose molecule, forming the following structure:
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The important points to note are:
 For bonding to occur, alternate glucose units must be inverted
 The bonding produces a very linear molecule because of the geometry of the CO-C bond angles.
Major Component of Biomass: A large proportion of the world’s biomass is in the form
of cellulose. In fact, it is the most abundant single polymer in the biosphere. Cellulose is
the main constituent of planet cell walls and the major structural component of woody
plants and natural fibres such as cotton, flax and hemp (wood is 50% cellulose, cotton
fibres are over 90% cellulose).
MAJOR TIPS
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Superior answers always have a correct diagram
Many people lose marks by not emphasising that it is the beta glucose monomer which
forms cellulose. The alpha glucose monomer forms starch.
Identify that cellulose contains the basic carbon-chain structures needed to build
petrochemicals and discuss its potential as a raw material
- Identify = recognise and name
- Discuss = identify issues and provide points for and/or against
- Starch is a useful alternative source for some chemicals we currently make from
petroleum e.g. ethylene and ethanol. Starch is a polymer of alpha glucose.
- Plants produce more cellulose than starch, so there would be greater benefits if we
could use cellulose as a source of materials we currently make from oil.
- Each glucose unit in cellulose has six carbon atoms joined together, so it has the basic
carbon-chain structure for making petrochemicals – molecules such as ethylene (2 C
atoms), propylene (3 C atoms) and butene (4 C atoms).
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It is more difficult to break cellulose into glucose than starch. This is because the long
near-linear chains of cellulose hydrogen bond to one another to form very compact
fibres, making it hard for chemicals to break the glycosidic bonds. However, there are
two processes to break cellulose into glucose:
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Digestion by cellulase enzymes: these exist in bacteria and certain fungi. The
process can be performed industrially by treating finely ground cellulosecontaining materials (e.g. old newspapers) with sodium hydroxide solution to
swell (open up) the cellulose fibres, then digesting with cellulase enzymes to
produce a solution of glucose.
 Digestion with strong acid: This involves heating a suspension of cellulosecontaining materials with concentrated sulfuric acid, which breaks cellulose into
glucose. Insoluble matter is filtered off, impurities removed, and the acid is
neutralised to produce a solution of glucose.
In both cases the solution of glucose is treated with yeast to form ethanol and if
required this can be dehydrated to ethylene.
The conversion of cellulose to ethanol and then ethylene requires high energy inputs (to
maintain the hot temperatures and operate machinery) which come from oil. Thus,
more oil would be used in making ethylene this way then is used by the direct cracking
of petroleum fractions.
Making ethanol from cellulose is more expensive than making it from starch or sugars,
despite the lower cost of the starting cellulose-containing material.
Explain why cellulose is a suitable raw material for the production of petrochemicals
Petrochemicals are carbon-based compounds, so substances used to manufacture petrochemicals must
also be carbon-based. Also, being a major component of biomass, cellulose is a readily available
renewable raw material for the production of petrochemicals.
Discuss the potential of cellulose as a raw material in the manufacture of petrochemicals
ADVANTAGES: Arguments put forward for the use of cellulose as a raw material include:
- Each beta glucose unit within cellulose has a basic 5 carbon atoms joined together which
can be used as the basic starting structure for petrochemicals.
 INCLUDE DIAGRAM OF BETA GLUCOSE
- Cellulose is a major component of biomass and is very abundant.
- Since cellulose is produced by living organisms it can be said to be renewable.
- Cellulose is biodegradable, and can be used to produce polymers such as rayon that are
mostly biocompatible and have a range of applications.
DISADVANTAGES: Arguments against the use of cellulose include:
- The use of food crops to make polymers presents ethical problems as there are people
starving in many parts of the world.
- Though cellulose is cheap, the conversion of cellulose to glucose using cellulase enzymes
or acid digestion is very costly and inefficient.
- The process requires an energy input that would be sourced from fossil fuels.
- Cellulose would require the growing of specific crops resulting in the loss of arable land
for crops; leaching and salinity may also result.
Therefore, cellulose has an ENORMOUS potential in the manufacture of petrochemicals as it is readily
available in huge amounts and can be converted to petrochemicals thus reducing our reliance of nonrenewable petroleum. This is important as petroleum supplies are running out.
ACIDIC ENVIRONMENT SAMPLE

Identify esterification as the reaction between an acid and an alkanol and describe, using
equations, examples of esterification
- Identify = name and recognise
- Esters are often sweet-smelling carbon compounds formed by the reaction between an
alkanoic acid and an alkanol. Esters include vegetable and animal oils and fats, natural
waxes, natural flavours and fragrances.
- Identifying: Esterification is the reaction between alkanoic acids and alcohols to produce
esters. This is achieved by the acid-catalysed reaction between an alkanoic acid (RCOOH)
and an alkanol (R’OH). As the two combine, a water molecule is ejected. In esterification,
the H atom of the alkanol joins with the OH group of the acid to form water. The
remaining OR’ group from the alkanol bonds to the carbon atom of the alkanoic acid
group to form the ester:
OR more simply (Conquering Chemistry),
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Describing Examples of Esterification (including equations)
Acetic (ethanoic) acid reacts with methanol to produce the ester methyl ethanoate and
water:
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Similarly, benzoic acid (C6H5COOH) reacts with ethanol to produce the ester ethyl
benzoate and water:
TALENT TIP: If asked for the products of the reaction take care not to forget water. Also be sure to
include the H2SO4 catalyst.
The flow chart shows a series of steps involved in the production of ethyl butanoate:
Glucose  ethanol mixture  pure ethanol  ethyl butanoate
Describe the chemistry and procedure involved in each of these steps, using diagrams where
appropriate (7 marks)
Glucose is fermented to produce an ethanol mixture. Yeast is added to the glucose solution under
anaerobic conditions as it provides the zymase enzyme which catalyses the process. Maximum yield is
achieved at 37OC and pH of 4-5 to prevent bacterial growth. This produces a 10% ethanol mixture:
C6H12O6 (aq) –(yeast zymase enzyme/37OC) 2CO2 (g) + 2C2H5OH (aq).
The ethanol is purified by distillation to 92% concentration. The process of distillation involves heating
the mixture until the ethanol boils at 78OC. The ethanol vapour is cooled and condenses and is separated.
Equipment setup:
To produce the purity of ethanol needed for esterification (98%), the alcohol is mixed with a dehydrating
agent, which is later recovered and reused. Pure ethanol is mixed with pure butanoic acid and heated
under reflux to produce the ester, ethyl butanoate.
The mixture is heated in a water bath so that the reactants reach their activation energy. To speed up the
process, concentrated sulfuric acid is added which acts as a catalyst and assists in the dehydration
process. Hydrogen is removed from the alkanol and hydroxyl from the acid so that they can link together
forming the ester. Water is the other product:
C2H5OH (l) + CH3(CH2)2COOH (l) (H2SO4/heat) CH3COO(CH2)3CH3 (l) + H2O (l)
The mixture is heated but this must occur without the loss of volatile reactants. The reaction is therefore
carried out by refluxing where the volatile substances are condensed in an upright condenser and are
returned to the reaction flask for further heating. Any excess acid can be neutralised using sodium
carbonate and the ester can be purified by distillation.

Describe the purpose of using acid in esterification for catalysis
- Catalysis = the use of a catalyst to change the reaction rate.
- Esterification is a slow process at room temperature and it doesn’t go to completion; it is
an equilibrium reaction (see examples above)
- Concentrated sulfuric acid (H2SO4) is used as a catalyst because:
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It increases the rate of the reaction by lowering the activation energy and
allowing equilibrium to be reached faster.
 It absorbs the water (acts as a dehydrating agent) as it is formed, shifting the
equilibrium to the right to minimise the disturbance (by Le Chatelier’s Principle).
This will increase the yield of ester.
Justification: Therefore, it can be seen that concentrated sulfuric acid has an important
role in esterification by acting as a catalyst and dehydrating agent.
Explain the need for refluxing during esterification
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Refluxing is the process of heating a reaction mixture in a vessel with a cooling
condenser attached in order to prevent loss of any volatile reactant or product.
Because the reactants and ester may be volatile (evaporate), esterification is carried out
using a refluxing apparatus. This prevents the volatile reactants and products from
escaping while being heated before the reaction has reached equilibrium. As the volatile
substances enter the condenser they cool, condense and fall into the reaction flask. This
allows esterification to occur at higher temperatures, increasing the rate of reaction. An
indirect heat source e.g. water bath is used to prevent flammable reactants and
products from catching alight.
An indirect heat source e.g. water bath is used to prevent flammable reactants or products catching
alight, and boiling chips (porous pot) are used to promote even boiling.
Explain the purpose of refluxing (2 marks) – TALENT 100
The esterification reaction is usually performed by “heating under reflux” because it:
1. Allows a reaction to occur rapidly at a high temperature. This increases the reaction rate as the
reactant molecules have more energy to overcome the activation energy of the reaction. (Many
reactions are extremely slow at room temp.)
2. Prevents volatile compounds from escaping from the reaction mixture (by returning them back
to the solution) while the reaction occurs
CONDITIONS FOR ESTERIFICATION: conc. H2SO4 and heat under reflux for 1+ hours