Chemistry

• (B) Increase in the rate of reaction
• Catalysts increase the rate of reaction by lowering the activation energy of the reaction.

• (A) Water
• Condensation of polymers consist of monomers with two electronegative substitutes, such as OH^- or Cl^-. Of the possible answers to this question, the only molecule that can be made from these substituent groups is water (H-O-H). The by product must contain at least one of these electronegative substituents - hydrogen and methane do not, and ethanoic acid is too large a molecule to be formed this way.

• (C) Chloroethene
• The monomer vinyl chloride has the structure CH₂=CClH. Its systematic name must contain the prefix 'eth', as there are two carbons, the root word 'ene', as there is a double bond between the carbons and the prefix 'chloro', as there is a chlorine substitute present. thus the name is Chloroethene. It is not necessary to add any numbers to designate the position of the chlorine, as there is only one substituent and only two carbons.

• (C) 2
• The reaction for the fermentation of glucose is
• C₆H₁₂O₆(l) --> 2C₂H₆O(l) + 2CO₂(g)
• Therefore, according to the stoichiometric coefficients, for each mole of glucose present at the beginning of the reaction, 2 moles of ethanol are produced.

• (B) Glucose
• Glucose is the monomer of cellulose. Both cellulose and glucose occur naturally. the polymer made from A (Ethylene) is polyethylene and no polymers are made from either benzene or ethanol (answers C and D).

(D) Lower nett levels of greenhouse gas emissions than petrol

This is the best answer, as it is most important to society that ethanol would have lower greenhouse gas emissions than petrol

• (C) The oxidation state of the iodine has gone from -I to 0 so the iodine has been oxidised.
• The student began with KI, in which the iodide has an oxidation state of -I, iodine crystals were formed in which iodine has the oxidation state of 0 (an element in its standard state). This reduction in oxidation number is evidence of reduction of the iodide to iodine. An increase in oxidation number would be evidence of oxidation.

• (D) The copper is a stronger oxidant than the iron hence copper ions gain electrons from the iron nail.
• The copper ions are being converted to copper metal. The observation that gives rise to this conclusion is that the iron nail is being covered in reddish brown coating and the blue of the copper sulfate solution is disappearing. if the copper is being reduced (going from oxidation state +II to 0), then the iron must be undergoing oxidation (going from an oxidation state 0 to +II). As the copper is being reduced, it must be an oxidant and the iron a reductant, as it is being oxidised and causing the copper to be reduced. When the iron is oxidised, it loses electrons and these are gained by the copper ions in the solution. In terms of strength of oxidant, the species that is reduced is the stronger oxidant.

• (C) The neutron to proton ration is too great.
• Many stable isotopes have a greater number of neutrons compared to protons. It is the ratio that is critical. However the ration for small atoms like carbon is very close to 1.0.

• (A) Neutron
• Uranium-238 has 92 protons while neptunium has 93. However, uranium is not bombarded with a proton. it is bombarded with a neutron and the nucleus then emits a beta particle.

• (C) Nickel
• The only metal in the answers that has a reduction potential smaller then that of iron (i.e. that is less reactive then iron) is nickel. The redox reaction of these two metals results in a positive voltage, which means a spontaneous reaction.

• (A) Glucose
• Glucose is the monomer of cellulose. Answer B is incorrect, as amino acids are the monomers of proteins.

• (D) Concentrated sulfuric acid
• The catalyst require for the dehydration of ethanol (and many other dehydration reactions) is concentrated sulfuric acid, The formation of the water as a product dilutes the sulfuric acid. Dilute sulfuric acid (C) is used as a catalyst in the hydration of ethylene to ethanol.

• (C) Cracking of long hydro carbons
• Ethylene can also be produced by the dehydration of ethanol but not by its hydration.

• (C) Interferometer
• An interferometer is used to detect the interference pattern from light beams.

• (A) Lanthanum-139
• When radioactive decay occurs, the sum of the atomic numbers on the left and right hand side of the equation must be equal, and the same is true of the mass numbers. The equation is
• ₀¹n + ₉₂²³⁵U --> X + ₃₅⁹⁴Br + 3₀¹n
• The main source of error in this question is that the student may fail to multiply the mass number of the neutron by three on the right hand side of the equation, thus getting answer B.

• (A) Propane and ethylene
• Propane and ethylene are significant byproducts of the catalytic cracking of petroleum. The fractions of petroleum are hydrocarbons and are broken into smaller hydrocarbons when cracked.

• (C) Poly(ethenylbenzene)
• The systematic name for polystyrene is poly(ethenylbenzene). The name of the monomer ethenylbenzene due to the presence of the ethenyl group (-CH=CH₂) on the bensene ring. The polymer is named by adding 'poly' before the name of the monomer and brackets around the monomer name, making only one word. Answer D also look correct because benzene is often drawn in the format of 1,2,3-cyclohexatriene but this is not correct.

• (B) The manganese gains electrons
• When permanganate is reduced to Mn²⁺ there is a reduction in oxidation number of the manganese from +VII to +II. This is a result of the manganese gaining 5 electrons.

• (C) Electrons travel from the anode to the cathode
• In a galvanic cell, oxidation (loss of electrons)occurs at the anode and reduction (gain of electrons) t the cathode. Therefore, electrons must travel from the anode (loss) to the cathode (gain).

• (C) Hydrogen-3
• At low atomic numbers, the relationship between the number of protons and the number of neutrons is closest to 1:1. The least stable of these isotopes is hydrogen-3, as there are 3 times as many neutrons as protons present in the nucleus, which is a very large difference.

• (D) Polymerisation
• Ethene (ethylene) is the monomer used in the production of the polymer poly(ethene) (polyethylene). No molecules are lost in the process.

• (A) Cellulose
• Biomass is largely composed of plant matter. Plant matter is largely composed of cellulose and lignin.

• (A) Low oxygen concentration and a temperature between 25^oC and 35^oC
• The presence of oxygen will allow decomposing bacteria to colonise in the mixture.

• (B) H₂SO₄
• Concentrated H₂SO₄ is the catalyst used to dehydrate ethanol, and dilute H₂SO₄ is used to hydrate ethylene.

• (A) Oxidation occurs in the anode.
• The anode is defined as the electrode where oxidation occurs no matter what the type of cell.

• (D) Curium
• Curium has an atomic number (96) beyond that of uranium (92). The others are not transuranic because they come before uranium in atomic number.

(B) Geiger counter

• (A) +1.1V
• In order to determine which electrode is the anode (oxidation) and which is the cathode (reduction) one must consult a table of reduction potentials. The combination that gives the highest positive voltage is the spontaneous reaction (recalling that the sign of the voltage must be changed when the equation becomes an oxidation, rather than a reduction, half equation). in this case the equation for the oxidation of zinc is;

Zn --> Zn²⁺ + 2e^- E⁰ = +0.76V

and the equation for the reduction of copper is;

Cu²⁺ + 2e^- --> Cu E⁰ = +0.34V

The overall voltage of the cell would be the sum of the oxidation and reduction half equation voltages, in this case E⁰_cell = +1.1V

• (C) Copper metal
• The anode is the site of oxidation. In this galvanic cell the copper is being oxidised and the silver ions reduced, as copper is a more reactive metal than silver. Thus, the copper metal electrode is the anode.

• (C) Propanol
• MM (propanol) = 60 g mol^-1, therefore = 60 x 33.6 = 2016 kJ mol^-1.

• (B)
• Cellulose is a polymer made up of beta-D glucose monomers. When linked together, every second monomer must be inverted.

• (D) Z > X > Y
• A more active metal will displace another metal's ions in solution. Z is the most active because it displaces Y²⁺ and is not displaced by X. Y is the least active because it is displaced by X and Z.

• (B)
• The double bond opens up and carbons link up to form a long chain. Every second carbon atom will contain a -CH₃ branch and a -COOCH₃ branch.

Crude oil is pre-heated before entering the fractionating tower. In the fractionating tower there are hundreds of bubble caps located on large trays that allow the separation.

More volatile components in petroleum bubble through these caps, rising higher up the tower or column where it is cooler. The compounds are separated as they go up the column because of their different boiling point ranges.

These compounds, or fractions, are drawn off at different levels in the tower.

Cracking is the process where high molecular weight saturated hydrocarbons are broken down into lower molecular weight hydrocarbons. These smaller hydrocarbons are often unsaturated. It is important because it can turn less useful fractions into more widely used shorter chain compounds. It can produce unsaturated hydrocarbons such as ethene. Ethene is the starting point for many important manufactured substances.

Thermal cracking achieves the process of breaking down long chain hydrocarbons by using very high temperatures. This is costly in terms of energy. By using suitable catalysts (catalytic cracking) the same effect can be obtained at lower temperatures.

(A) CH₃CHCH₂ or C₃H₆

(B) Propylene has an extra carbon and two extra hydrogen atoms. Its boiling point should be greater then that of ethylene as its molecule is larger.

(C) Both are unsaturated hydrocarbons, each with just one double bond and the ratio C:H is 1:2.

• C₁₅H₃₂ --> 2C₂H₄ + C₃H₆ + C₈H₁₈

Its double bond has a high electron density making it very reactive to many chemicals, It is also small enough to act as the basic building block from which to 'grow' new compounds.

CH₂CH₂ + H₂O --> C₂H₅OH

CH₂CH₂ + HCl --> C₂H₅Cl

H₂SO₄

H₂O

4Na + Pb + 4C₅H₅Cl --> Pb(C₂H₅)₄ + 4NaCl

Unsaturated hydrocarbons will rapidly decolourise bromine water. They also fade the colour of acidified permanganate solution.

1,2-dibromoethane

As bromine is toxic, using in it reactions should occur in the fume cupboard and you should wear gloves and goggles to prevent getting any of it on you. Hydrocarbons are flammable and should be kept away from naked flames and should not be disposed of down the drain when the experiment is concluded.

• (A) 1,2-ethandiol OR ethan-1,2-diol
• (B) Saturated
• (C) The Mn²⁺ ion in solution is colourless, as is ethan-1,2-diol.

Weak forces of attraction between uncharged molecules with full electron shells. The strengths of the force increases as that total number of electrons in the molecule becomes larger.

As the length of the molecule increases there are more sites for these weak dispersion forces. Consequently, a greater force needs to be overcome before the substance will melt.

• (A) 2,2-dimethylpropane
• (B) No. The molecular shape influences melting and boiling points. Depending in its packing, the strength of the dispersion forces will be affected.

It is a small molecule and its double bond can easily be opened to produce 'sticky' ends that can join with a whole host of compounds to form polymers.

• (A) Polymerisation that requires two or more functional groups joined together by simple addition.
• (B) In condensation polymerisation a small molecule, usually water, splits out when two monomers join together. No such substance splits out with addition polymerisation.

Five drops of cyclohexane was added to 2 mL bromine water in a test tube and shaken. Decolourisation would indicate the presence of the double bond and identify the chemical as alkene. The investigation was repeated with cyclohexane and all variables such as volume and temperature were held constant so that a comparison could be made. This was carried out in a fume cabinet because bromine is volatile and poisonous. Cyclohexene and cyclohexane were used because the are liquids and as such are easier to handle than gases and they vary only by a double bond so that either variables will not influence the results. Bromine is used because it will readily react with a double bond but not single bonds.

• (A) Chloroethene
• (B) It can be used as a packing material around electrical appliances when they are transported because it absorbs shock.
• It can be used to make foam cups for hot tea and coffee because its a good heat insulator.

• (A) Addition
• (B) Flor low density poly(ethylene), the reaction is initiated with an organic peroxide catalyst. The ethylene is subjected to extremes of temperature and pressure. Pressures of about 2600 atmospheres liquify the gas. The reaction container must be kept cool because the reaction releases large amounts of heat.The final product is extruded and formed into pellets which can be melted and moulded into products.

(A) A condensation polymer is a long chain molecule produced from smaller molecules (monomers) via the removal of a small molecule (often water)

(B) polypeptides are condensation polymers produced by the formation of successive peptide bonds between amino acids.

(A) The substance which dissolved in ethanol were mainly polar substances.

(B) Ethanol is a polar substances and since like dissolves like, ethanol dissolved the polar substances studied.

• (C)
• i) Ethanol has a good octane rating. it produces far less nett greenhouse gases than petrol when combusted and it i a renewable source of energy. Countries that have no oil reserves may be able to grow sugar to make ethanol for fuel, thus saving on foreign currency.

ii) Ethanol is still in its developing/testing stage. It has shown good promise so far, with some local petrol stations blending it with their petrol, e.g Biogas. It has been phased in as an alternative fuel source in Brazil where it is proving efficient. Its high costs of production are a drawback at present and this has contributed to its lack of development in Australia.

(A) We collected a sample of the following alkanes in test tubes: hexane and cyclohexane. We also collected a sample of the following alkenes in test tubes: cyclohexene and hexene. We add some bromine water to each set of test tubes. We recorded any colour changes we could see in any of the test tubes.

(B) The alkanes did not react with the bromine water. The alkenes reacted with the bromine. We could tell because of the decolourising of the solutions. The halogens ass across the double bond of the alkenes hence the solutions decolourise as colourless 1,2-diobromo-alkane.

(C) We selected hexane and cyclohexane because they are both alkane s that are liquid at room temperature. It was necessary to select liquids in order to observe the colour changes upon addition of bromine water.

Vinyl chloride (chloroethylene)

Addition

Toxic fumes and poisonous HCl gas is liberated.

By selectively using additives in the manufacturing process.

Polyethylene is produces when two ethylene monomers combine but no extra atoms are needed. In polystyrene a benzene ring, minus one hydrogen, (a phenyl group) replaces a hydrogen atom on the ethylene monomer.

It is light and it a thermal insulator for the hot liquids it is meant to hold. As Styrofoam is inexpensive to make, the cups are disposable and suitable for common use.

• An ALKANE is a hydrocarbon with
• ONLY single bonds between the carbons.

• An ALKENE is a hydrocarbon with 1
• or MORE double bonds between carbons.

• Also recall:

• Petroleum (crude oil) is a complex mixture
• of hydrocarbons consisting mainly of alkanes and smaller quantities of other hydrocarbons such as alkenes.
• - When petroleum undergoes fractional distillation, some fractions, particularly petrol, are in demand and of high economic value.
• - Other fractions, consisting of larger molecules than in petrol and of low value, can be passed over a heated catalyst that cracks the larger molecules into smaller molecules.
• -- A major by-product of this catalytic cracking is ethylene.

• Ethylene (systematic name: ethene), C2H4,
• is one of the most useful substances in the petrochemical industry, and is in extremely high demand.
• - Ethene is the most widely used raw material for the production of synthetic organic products such as
• plastics, pharmaceuticals, insecticides and industrial chemicals.

• Cracking is the process of ‘breaking’
• large hydrocarbon molecules into smaller length chains, using heat (Δ).
• - Cracking always produces an alkane and an alkene
• - i.e. the cracking of pentane into ethylene and propane:

Reason for Cracking:

• - In refineries, the output of products DOES NOT match the economic demand; ETHYLENE is in very high demand, but it only makes up a very small
• percentage of crude oil.
• - To match the demand for ethylene, low-demand, long-chain hydrocarbons are ‘cracked’ and ethylene is produced.
• - There are two forms of cracking:
• - Catalytic cracking
• - Thermal cracking

• Catalytic Cracking:
• - In this process, carried out in a ‘cat-cracker’, long alkane molecules (C15 - C25) are broken into just two molecules, an alkane and an alkene.
• - This form of cracking uses a
• CATALYST to break the alkanes.
• - The catalyst used are zeolite crystals:
• - Zeolites are aluminosilicates (compounds made of aluminium, silicon and oxygen), with small amounts of metal ions attached. They are highly porous heterogeneous catalysts with a massive surface area
• - The reaction is carried out at 500°C, in the absence of air, with pressure just above atmospheric pressure.
• - This process uses less heat than THERMAL cracking, but it cannot decompose large molecules completely into ethylene, so it is insufficient in meeting the demands of the industry.

• Thermal Cracking:
• - Also called ‘steam’ cracking.
• - This process does not use a catalyst, only very high temperatures.
• - The long-chain alkanes are passed through metal tubes at temperatures of 700°C to 1000°C, at pressure above atmospheric.
• - The alkanes are decomposed completely into ethylene and other short chains.
• - The use of steam is that is allows for easy flow of hydrocarbon gases, it dilutes the mixture to create smooth reactions, and it removes carbon deposits in the metal tubes.

• - Ethylene has a highly reactive
• double-bond; It is a site of very HIGH ELECTRON DENSITY.

• - The presence of a double bond
• allows atoms to be added to the ethylene molecule.

o This is very useful as it means that a variety of substances can be produced from ethylene.

• o In this process, the double bonds between carbon atoms are broken and additional atoms or functional groups are added to either side of the double bond, resulting in the formation of a saturated hydrocarbon:
• These reactions that ethylene undergoes are known as ADDITION reactions, where one bond in the double bond is broken, and the two atoms in a diatomic molecule are ‘added’ on.

• There are many types of addition
• reactions:

• o Hydrogenation: Hydrogen is reacted with ethylene, using a platinum catalyst at
• 150°C. The product is ethane.

• o Hydration: Ethylene is reacted with water, using phosphoric acid as a catalyst, to produce ethanol. This is an industrially important reaction.

o Halogenation: Reactive molecules from the halogen group (Fl2, Cl2 and Br2) can all react with ethylene. EG: Chlorine molecule reacting with ethylene forms 1,2-dichloroethane.

• o Hydrohalogenation: In this reaction, a hydrohalogen (such as HCl or HFl) and
• ethylene react to form a halo-ethane. EG:
• HFl reacting with ethylene forms fluoroethane.

The MAIN advantage of the double bond is that ethylene can undergo polymerisation, a very important reaction that will be discussed later.

There is a distinct difference between the chemistry of alkanes and that of alkenes. Alkanes react slowly, by the process of substitution; while alkenes act readily, by the process of addition. This difference in reactivity is used as the chemical basis for this experiment.

• Aim: to distinguish between an alkene
• and an alkane, based on its reactivity to bromine water.

Method:

- Accurately measure 1mL of cyclohexane and cyclohexene

- Pour each solution into two separate test tubes

• - Using a dropper, drop 3 drops of bromine water into each test
• tube.

- Observe, record results

RESULT:

• - It was observed that cyclohexene turned the bromine water
• colourless, whereas the cyclohexane solution remained yellow.

• - Thus ONLY cyclohexene reacted with the bromine water, and thus the
• alkene was said to be more reactive than its corresponding alkane; this is due
• to the double bond of the alkene.

• Reaction:

JUSTIFY the method:

- Cyclohexene and cyclohexane were used, instead of ethylene or propene because C1 to C4 are gases at room temperature, and would be hard to manage; cyclohexene is liquid at room temperature.

- Also cyclohexene/ane was used instead of hexene/ane because cyclic hydrocarbons are more stable than their linear counterparts.

LIMITATIONS of the method:

• - The alkane reacted slightly, as UV radiation caused slow
• substitution reactions.

SAFETY precautions:

• - Bromine water is highly toxic if ingested, and is slightly
• corrosive.

• - Cyclohexene and cyclohexane are both poisonous if ingested, and
• both give off fumes, as they are highly volatile and highly flammable.

• - Polymerisation is the chemical reaction in which many identical small molecules combine to form one
• very large molecule.

- A monomer is a simple molecule that can be bond to other monomers to form a polymer.

- A polymer is a macromolecule containing repeating subunits, monomers, joined together with covalent bonds.

- Because of its reactive double bond, ethylene is able to undergo polymerisation; ethylene, a monomer, forms the polymer poly(ethylene).

• - In an addition polymerisation reaction, no additional molecules (e.g. water) are produced – there is no gain or loss of atoms, the double bond
• simply ‘opens’ and monomers attach.

• - Polyethylene is an addition polymer, as the ethylene molecules combine with each other in the following way:

• - As can be seen, no extra molecules are produced. A more realistic representation of the polyethylene
• polymer (with nine repeating units) is:

- In this experiment, molecular modelling kits were used to show how polyethylene is produced through the polymerisation of ethylene.

- The class was divided into groups, and each group was provided with a kit.

- 3 ethylene monomers were created by each group, with black balls representing carbons and smaller, white balls representing hydrogen.

- Then the monomers were ‘polymerised’: each group combined their monomers with every other group until a large chain was created – a section of polyethylene.

JUSTIFY the method:

o The models created a 3D representation of the chemical process, which led to greater understanding of polymerisation.

o The use of ball-and-stick models, depicting the double-bond with flexible rubber rods, greater increased understanding of the process.

LIMITATIONS of the method:

• o The model only provided a very limited section of a polyethylene
• molecule, as there were limited numbers of kits.

• o The use of catalysts (such as Zeigler-Natta catalysts) was not shown in
• the process, and thus it was not completely accurate.

- Ethylene is a commercially and industrially important polymer.

- There are two methods for its production:

• o High Pressure Method: In this process, ethylene is subjected to pressures of 100-300 MPa, with temperature in excess of 300°C. A molecule, called the initiator, is introduced, usually a peroxide. The initiator starts off a chain-reaction, creating the polyethylene macromolecule.
• - This process creates BRANCHED chains of polyethylene that cannot be packed together tightly. Thus branched polyethylene is called low-density polyethylene (LDPE).

• o Ziegler-Natta Process: This process uses only a few atmospheres of pressure and temperatures of about 60°C. A catalyst is used: it is a mixture of
• titanium (III) chloride and a trialkylaluminium compound.

• - This process creates UNBRANCHED
• chains of polyethylene that can be packed together very densely. Thus unbranched polyethylene is called high-density polyethylene (HDPE).

- The steps taken to produce the polymer are the same in both methods, but the initiator molecule is different:

• o INITIATION: The initiator molecule is added to the ethylene container; in the diagram below, it is shown as a peroxide radical (an oxygen compound with a free electron). The initiator reacts with
• one ethylene molecule, breaking its double bond, and attaches to only ONE bonding site, creating an ethylene-initiator RADICAL. The “dot” represents a free, highly reactive, electron.

• o PROPAGATION: Another ethylene monomer
• attaches to this radical, opening another bonding site, then another attaches, and so on, rapidly increasing the length of the chain. One of these reactions:

• - Repeating this reaction many times gives a general formula:

• o TERMINATION: The reaction stops (terminates) when two such chains collide and the two radicals react, forming a longer chain. This is a random process, so the length of polyethylene chains can vary greatly. (The peroxide initiator is eventually engulfed by the reaction, and so is no longer present at termination):

Low-Density Polyethylene (LDPE):

• o Plastic cling wrap/food packaging; because it is tough, flexible, transparent, non-toxic. As LDPE
• is permeable to O2 and CO2 but not to water these films keep foods fresh and prevent them from drying out.

o Disposable shopping bags; because it is cheap and relatively strong

o Milk bottles; as it is non-toxic, cheap, un-reactive and recyclable

o Insulation of wire and cables: non-conductor, reasonably strong

High-Density Polyethylene (HDPE):

o Kitchen utensils and containers; as it is strong and non-toxic

o Containers for petrol, oil, detergents, acids and solvents: chemical resistance, strong

o Rubbish bins; it is rigid, only slightly flexible and hard

o Pipes and other building materials; it is rigid, hard, and un-reactive

o Children’s toys, plastic buckets, lunch boxes and playground equipment: durable and tough

o Can be made into tough films, i.e. freezer bags.

Polyvinyl Chloride (PVC):

o Pure PVE is not a useful plastic as it is hard and very brittle and tends to decompose when heated; however, the inclusion of other additives to improve its flexibility and thermal stability greatly extended its range of uses.

o Garden hoses; it can contain UV inhibitors; it is relatively un-reactive, flexible, and durable. Can be softened with plasticisers.

o Pipes and guttering; it is very rigid and hard, and un-reactive. It is also easily shaped.

o Building industry for external cladding, guttering and down pipes, electrical conduit, waste water pipes, rigid panels and floor tiles: ridgid, hard, un-reactive, easily shaped

o Kitchen utensils, credit cards: strong, non-toxic

o Upholstery coverings for cars and furnishings, electrical insulation and garden hoses: can be made flexible

• o Bottles: impervious to oils and most
• organic materials

Crystal Polystyrene:

o CD cases, cassette tapes; used because polystyrene is transparent, brittle, hard, rigid, easily shaped, and is a good insulator.

o Screw driver handles and kitchen cupboard handles; very durable and strong, hard and inflexible.

o Using different production techniques can be used to produce products including computer and TV cabinets, wall tiles and study furniture.

Expanded Polystyrene:

o Packaging, and disposable cups; it is light (full of air), cheap, and it is a thermal insulator

o Boogie boards and the cores of surfboards: lightweight, cheap, low density

o Sound-proofing; it is a shock absorbent material, light, easily shaped, excellent insulator

RECALL:

• - Addition polymers form NO extra molecules when their monomers join
• together.

• - This type of polymerisation reaction occurs due to a double-bond
• opening, creating 2 new bonding sites.

- There is an overwhelming need for alternative sources of compounds that are presently derived from the petrochemical industry (i.e. crude oil).

- This is because crude oil is a fossil fuel, and is hence a non-renewable resource.

- Based on current usage statistics, crude oil reserves could be completely used up within a few decades.

• - Compounds obtained from the
• petrochemical industry have two uses:

- The production of energy: 84% of crude oil is used to produce energy. This includes petrol and diesel for cars, heating oil, jet-engine oil and LPG.

- The production of materials: The other 16% is used to produce polymers, pharmaceuticals, and other extremely important chemicals.

- Some of the materials created from crude oil cannot be derived by any other ways (or would be much too expensive to synthesise), so once crude oil is exhausted, there will be no way to produce them.

• - It has been argued that alternative fuels be created so that crude-oil can be reserved for use by the
• petrochemical industry to create materials.

- The increasing cost of crude oil in this current day and age is another factor.

- Also, many countries that contribute a significant portion of the world’s crude oil are very economically and politically unstable, with fragile infrastructure, and supply from these countries can be very erratic.

- One of the most appealing replacements for crude-oil derived compounds is cellulose; this is because it contains all the carbon-chain structures needed for the production of materials, and it is so remarkably abundant on Earth.

- A condensation polymer is a polymer that produces EXTRA molecules (usually water) when its monomers combine.

- Examples include natural polymers such as cellulose, starch, protein, DNA, and manufactured polymer fabrics such as silk, polyester and nylon.

- In condensation, the monomers react differently than in addition reactions.

- There is no double-bond that opens (as in addition); the FUNCTIONAL GROUPS of the two monomers react together, forming a new bond and water.

- i.e. Cellulose:

o Cellulose is a natural polymer formed through the polymerisation of glucose

• o Glucose, C6H12O6, is the monomer in this
• polymer.

• o The reaction occurs between 2 hydroxyl groups, forming a glycosidic bond

o As can be seen, the reaction sites are the hydroxyl (OH^-) groups on the first and fourth carbons (C1 and C4).

o Each glucose molecule has 2 reaction sites; that is why it can polymerise.

o One C-OH bonds to another C-OH, forming a C-O-C bond (glycosidic bond).

o The left over H+ and OH- combine, forming water.

- Cellulose is a naturally occurring condensation polymer (a biopolymer)

- It is the single most abundant polymer on Earth, making up about 50% of the total biomass of the planet (biomass is the mass of all organisms in a given area).

• - It is long polymer chain made of
• repeating glucose monomer units, which FLIP for every alternate glucose,
• as can be seen in the above diagram.

• - Above, the structure of glucose is quite cluttered. To demonstrate a section of a cellulose chain, a simplified form of glucose will be used.

- Glucose; in short-form:

o It is assumed that at every corner, there is a carbon atom.

o Hydrogen atoms are not shown, but are also assumed to be there, and are deduced by knowing that carbon makes 4 bonds.

• o Hence, the structure of cellulose can be shown as:

- As can be seen, it is a very linear molecule, due to its straight chains.

- The close packing of its beta linkage ribbons and the strong hydrogen bonds between them gives cellulose its great strength and rigid structure.

- The attraction between the hydroxyl (-OH) and hydrogen (-H) groups of the adjacent cellulose molecules result in the formation of hydrogen bonds which bind the molecules in a regular crystal-like lattice.

- The BASIC carbon-chain structures that are used to make petrochemicals are short-chained alkenes such as ethylene (2C), propene (3C) and butene (4C)

- Glucose, the basic structure in cellulose, is a 6C molecule.

• - Hence it has to potential to be
• transformed into the above compounds.

- The Potential of Cellulose as a Raw Material:

o Although theoretically, cellulose can provide limitless amounts of renewable raw materials, this is currently too expensive and impractical.

o This is because in order to derive ethylene, etc., from cellulose, firstly, cellulose must be broken into glucose (using either bacterial digestion or acidic decomposition), then fermented (with yeast) into ethanol and then dehydrated (using H2SO4) into ethene; this is a lengthy and expensive process.

o Hence, cellulose has great potential, but is currently not economical.

• - Name of Biopolymer: Biopol™
• o It is made of polyhydroxybutyrate
• (PHB) and polyhydroxyvalerate (PHV).

• - Organism Used:
• o Alcaligenes eutrophus (a bacterium).

• - Production:
• o In industrial production, A. Eutrophus is grown in an environment favourable to its growth to create a very large population of bacteria (such as high nitrates, phosphates and other nutrients).

o When a sufficiently large population has been produced, the environment is changed to one that is high in glucose, high in valeric acid and low in nitrogen.

o This unnatural environment induces the production of the polymer by the bacterium; the polymer is actually a natural fat storage material, created by the A Eutrophus in adverse conditions.

o Large amounts of a chlorinated hydrocarbon, such as trichloromethane are added to the bacteria/polymer mix; this dissolves the polymer.

o The mixture is then filtered to remove the bacteria.

o The polymer is extracted from the hydrocarbon solvent as a powder, which is then melted or treated further to create a usable polymer.

• - Properties:
• o It is BIODEGRADABLE and BIOCOMPATIBLE

o It is non-toxic, insoluble in water, permeable to oxygen, resistant to UV light, acids and bases, high melting point, high tensile strength

• - Uses in Relation to Properties:
• o It has many medical applications (e.g. biocompatible stiches that dissolve or are absorbed by the body)

o Disposable containers for shampoo, cosmetics, milk bottles, etc., as it only takes 2 years to decompose back into natural components

o Disposable razors, cutlery, rubbish bags, plastic plates, etc.

• - Advantages:
• o It is biodegradable, unlike polyethylene and other petroleum derived plastics, and so will help to reduce levels of rubbish in land fills

o It is compatible with organisms (biocompatible); it is not rejected by the body’s immune system and so can be used safely

o It is a renewable resource

• - Disadvantages:
• o It is currently very expensive, and currently the demand is not high enough for it to be economically viable

• - Future Developments:
• o Recently, the gene for producing Biopol polymer strands from the Alcaligenes Eutrophus bacteria was extracted and implanted into E. coli using genetic engineering techniques. E. coli bacteria are much easier to grow than other bacteria, and thus are cheaper.

• o Nutrient sources are starting to be derived from waste materials, such
• as molasses and other agricultural wastes. This greatly reduces costs.