Chemistry – Production of Materials Fossil fuels provide both energy and raw materials such as ethylene, for the production of other substances.

Construct word and balanced formulae equations of chemical reactions as they are encountered

Complete Combustions:Wood + oxygen water + carbon dioxide

Methane + oxygen carbon dioxide + waterCH4(g) + 2O2(g) CO2(g) + 2H2O(l)

Cellulose + oxygen water + carbon dioxide (C6H10O5)n + O2 H20 + CO2

Identify the industrial source of ethylene from the cracking of some of the fractions from the refining of petroleum

Ethylene = ethene, C2H4, the lightest alkene (ethene is the systematic name for the more familiar “ethylene”);Petroleum = crude oil and natural gas; mixtures of hydrocarbons formed from the anaerobic decay of the remains of ancient unicellular marine organisms;Refining = making pure, removing contaminants (in the case of petroleum, separating pure substances from the mixture by fractional distillation);Fractions = components of the mixture;Cracking = the breaking of large hydrocarbon molecules (eg. decane C10H22) into smaller ones.

Ethylene originates from crude oil which is obtained from the biomass. Crude oil is taken to a fractional distillatory and distilled to separate large hydrocarbons from small one and these large hydrocarbons are processed into cracking which involves breakdowns of the hydrocarbon into smaller ones through heating the alkane to high temperatures in presence of a catalyst (catalytic cracking) which is zeolite. - This cracking process increases the rate of producing today’s petroleum.- It is used because of it is more efficient costly and economically. - The cracking of large hydrocarbons results in the production of ethylene.

Cracking is the name given to the chemical process of breaking large hydrocarbon molecules into smaller ones; e.g. dodecane breaking into octane and further into butane. - There are two types of cracking: catalytic and thermal cracking.

Thermal cracking:- Steam cracking/thermal cracking is a non-catalytic process in which a mixture of alkanes with steam is passed through very hot metal tubes reaching to temperatures from 700-1000⁰C- At just above atmospheric pressure to decompose the alkanes completely into small alkenes such as

ethylene, propene, butene. Hydrogen is also produced. - It involves heating alkanes to high temperatures in the absence of air as oxygen in the air will cause alkanes to combust breaking the covalent bond between the compounds and would form two new molecules.

Incomplete Combustion:Propane + oxygen Carbon monoxide + water2C3H8 + 7O2 6CO + 8H2O

Propane + oxygen carbon monoxide + soot + waterC3H8 + O2 2CO + C + 4H20

Fritz Haber’s equation for ammonia:N2 + 3 H2 →(reversible) 2 NH3 (ΔH = −92.4 kJ·mol−1) ~3% product in 21 days - with iron catalyst and 300-500⁰C medium temperature, 30% product in 1-2 hrs.

Sulfur dioxide + oxygen (reversible) sulfur trioxide Catalyst: vanadium pent oxide into 1 atmospheric pressure.

Steps in thermal cracking:1. Initiation **Ra(radical) + CH2=CH2 -> RaCH2CH2 (radical)

2. Propagation **RaCH2CH2 (radical) + nCH2=CH2 -> Ra(CH2=CH2)n(radical)

3. Termination **Ra(CH2=CH2)n(radical) + Ra(CH2=CH2)n(radical) -> Ra(CH2-CH2)nRa

Catalytic cracking:- The process in which high molecular weight (high boiling point) fractions from crude oil are broken into lower molecular weight(lower boiling point) substances in order to increase the output of high-demand products. - Same as thermal cracking however it involves a catalyst such as zeolite – an aluminium silicate which has a large surface area which reduces the amount of heat needed to crack molecules.

Identify that ethylene, because of the high reactivity of its double bond, is readily transformed into many useful products.

Property Alkanes AlkenesGeneral formula C2H2n+2 C2H2nCommon Name Paraffin OlefinsType of molecules Saturated (max no. of

hydrogen)Unsaturated

Isomers Yes YesDissolve in Non-polar solvents Non-polar solventsHow obtained Fractional distillation Fractional distillation

Alkenes, as shown has similar physical properties of boiling points, densities, and solubilities to its corresponding alkanes. This is because alkenes, like alkanes are non-polar molecules with weak dispersion forces being the only intermolecular forces involved. E.g. ethylene, propene and the butenes are gases at room temperature as are the corresponding alkanes and the higher alkenes are liquids, like the alkanes.

But, alkenes and alkanes differ in their chemical reactivity. ..- Alkenes are double carbon-carbon bonds, and ethylene is a form of this and hence is very reactive.- Alkenes are more reactive than alkane’s s as alkenes have two extra free electrons that allow a more reactive form of its double bond. - All reactions in alkenes take place at the double bond, whereas alkanes can have the reaction taking place anywhere as they undergo only a substitution reaction. . - Alkenes reacting with many substances are called addition reactions where an alkene and a molecule react to form single bonds. This is done with a catalyst.

In terms of the ethylene’s intramolecular bond, the two bonds of ethylene are not identical. The second bond is weaker than the first bond and this, only a small amount of energy is required to enter the system in order to convert the double bond into a single bond, resulting in ethylene’s/ ethene’s high reactivity.

Identify that ethylene serves as a monomer from which polymers are made.

Polymers refer to the double bonds – (-enes). They are referred to as macromolecules with over 50 carbon bonds. They are built from the common monomers- ethene and propene. A monomer is a micro-molecule with small carbon chains approximately 1-5.

Ethylene is a monomer of polyethylene as shown.

Polyethylene can be produced by high pressure and low pressure methods. (Note: Polyethylene is a common name for polyethene). When ethylene has been converted to polyethylene it is often made into plastics. There are two types of polyethylene which is industriously used.

LDPE: - Branched chains - they are moved further apart and have a low density, - Soft and flexible- Have a weak dispersion force because of the branched chains

HDPE : - Dense, hard and rigid. - Consist of unbranched chains and are straight- they can be closely packed together because of this - High density and in turn creates a stronger dispersion forces. - They can be used for toys, bins, boats, canoes, and buoys.

Low Density Polyethylene High Density PolyethyleneProperty Low density High densityMolecular weights Low (1million g/mol) High (3 million g/mol)MPs ~80⁰C ~135⁰CColour Transparent Translucent; whiteCrystalline regions Low HighUses Glad wrap, flexible plastic bags,

squeeze bottlesBowls, buckets, wheely bins.

Identify polyethylene as an addition polymer and explain the meaning of this term.

Polymers are made by adding double bonded molecules to each other resulting in no other product under the presence of a catalyst however; the double bond is broken into a single chain. Addition polymerisation is the process of this in which identical small molecules combine to form one large molecule, with no by-products.

Outline the steps in the production of polyethylene as an example of a commercially and industrially important polymer.

The steps taken to produce polyethylene from ethylene: Initiation:- Under extreme heat and the presence of a catalyst, the double bonds in ethylene break down and become reactive with the help of organic peroxide. - Radicals are compounds with free ends. - E.g. C10H22 CH3(CH2)4 • (pentyl free radicals)

Propagation:- The free radicals decompose to produce smaller free radicals and release alkenes such as ethene and propene. This mimics a group of reactive ethylene’s joining together in a head to tail like arrangement.- (from previous example) CH3(CH2)4 • CH3(CH2)2 • + C2H4 (ethene and propyl radical)

Termination of the free radicals:- When sufficient monomers are linked, the process ends by allowing two hydrogen molecules to join at each ends of the polymers hence eliminating the radicals. - Free radicals may react with other free radicals to form hydrocarbons - CH3(CH2)2 • + CH3(CH2)2 • C6H14 (two propyl radicals make hexane).

Another cracking process is done through heating ethane. Ethane can be cracked to form ethene and 9% of this gas coming from South Australia is done in this manner being purified and cracked into this form.- C2H6 (g) C2H4(g) + H2 (g)

Identify the following as commercially significant monomers: vinyl chloride and styrene by both their systematic and common names.

Describe the uses of the polymers made from the above monomers in terms of their properties.

PVC: - An unsaturated monomer (vinyl chloride) combined to form its polymer - It is thermoplastic, since it is branchedo One that can be heated and moulded. Thermoplastics can be set and remoulded many times.

- The chlorine group attached to every second atom o The chlorine group adds an extreme amount of molecular weight and hence makes its MP and BP more resistant to heat compared to a polyethylene. - It is used in piping, gutters and credit cards. It is also good for electrical insulation, garden hoses, and packaging material- PVC is moderately resistant to chemicals and is very useful for food packaging. - It is a good electricalor heat insulator - Stiff and rigid due to the Chloro-side group - By adding different chemicals, PVC can change and increase its properties drastically.o Plasticiser softens the plastico Heat stabiliser doesn’t break down as readily to heat and so becomes heat resistant and shock absorbento Flame retardant which lowers flammability o UV absorber which prevents UV decomposition

Polystyrene: - An unsaturated monomer (styrene) which combines to form its monomer. - The benzene group is attached to every second carbon atom o The benzene ring is a very heavy attachment and contributes a major part of the molecular weight. o This is why it has a firm and stiff structure as a polymer as when the molecular weight increases the MP and BP increases, hence it is more resistant to heat to change its state. - Polystyrene is often turned into Styrofoam by blowing gas through it while it is at high temperatures and whilst in liquid form - Styrofoam is used in packaging, container, cups, insulation and beam bags. - It is a good electrical and heat insulator since it has no free electrons to conduct electricity. - It is very stiff and strong due to the large benzene side group and therefore is used to make screwdriver handles, etc. - It can be turned to low density Styrofoam by blowing air molecules through it.

Gather and present information from first hand or secondary sources to write equations to represent all chemical reactions encountered in the HSC course.

Alkane

Thermal Cracking:

Cracking of Decane

Chemical Equations

C10H22-> 2C5H11 (radicals)

C5H11 (radical) -> C3H7 (radical) + C2H4

2C3H7 (radical) -> C6H14

** example of the thermal cracking (in the previous dot point)

Word Equations

Decane -> Pentyl radicalsPentyl radicals -> Propyl radical + EthenePropyl radical -> Hexane

Cracking of ethane

Chemical Equations

C2H6 (g) -> C2H4 (g) + H2 (g)

Δ  H = +138 kJ/mol

Word EquationsEthane -> Ethene + Hydrogen + 138 kJ/mol Energy

Catalytic cracking

Catalytic cracking of Decane

Chemical Equations

C10H22 (l) -(zeolite)1> C2H4 (g) + C8H18 (l)

Word Equations

Decane -(zeolite)> Ethene + Octane

Addition Reactions2

Hydrogenation

Chemical EquationsC2H4 (g) + H2 (g) -(nickel)> C2H6 (g)

Word EquationsEthene + Hydrogen -(nickel)> Ethane

Hydrohalogenation

Chemical EquationsCH2CH2 (aq) + HCl(aq) -> CH3CH2Cl(aq)

Word EquationsEthene + Hydrochloric Acid -> Chloroethane

Production of Ethanol (also hydration reaction)

Chemical EquationsCH2CH2 (aq) +H2O(l) -(H2SO4)> CH3CH2OH(aq)

Word EquationsEthene + Water -> Ethanol

Oxidation

Production of Vinyl Chloride

Chemical Equation

4CH2CH2 (g) + 2Cl2 (g) + O2 (g) -> 4CH2CHCl(g) + 2H2O(g)

Word EquationEthene + Chlorine + Oxygen -> Vinyl chloride + Water

Alkylation

Production of Styrene

Chemical EquationsC6H6 + CH2CH2 -> C6H5(C2H5)C6H5(C2H5) + S _> C6H5(CHCH2) + H2SFootnotes1. Zeolite is an aluminium silicate that provides a high surface area for reaction note that although it is advantageous because cracking can occur at lower temperatures of 500oC, only small molecule products such as ethene or propene can be obtained.2. note equations all relating to substitution and addition reactions must be known

Reactions breaking the double bond:- Oxidation – addition of oxygen across the double bond (no specific catalyst but are used often when alkenes are oxidized – Ag and CuCl2)o E.g. ethylene to ethylene oxide- Halogenation – addition of one of the halogens (fluorine, etc.) (catalyst is used for substitution reactions – UV light)o E.g. conversion of ethylene to 1,2-dichloroethane- Hydration – addition of water across the double bond (catalyst of dilute sulphuric acid)o E.g. Ethylene to ethanol- Dehydration – extraction of an alcohol to form an –ene and a water molecule (catalyst of concentrated sulphuric acid). - Polymerisation – joining up of lots of molecules to form a long chain like molecule. - Alkylation (addition of a carbon chain to the double bond)o E.g. the synthesis of ethylbenzene from ethylene and benzene

Substitution Reactions:For alkanes, the reactions are a lot slower often needing a catalyst which is often UV light. Reactions with alkanes are called substitution reactions as they substitute for a hydrogen on a molecule.

For e.g.: the chlorination of hexane where a hexane combines with bromine water to form bromcyclohexane and HBr.C6H12 + Br2 C6H11Br + HBr.

Summary of the equations (structural form):

Identify data, plan and perform a first-hand investigation to compare the reactivity’s of appropriate alkenes with the corresponding alkanes in bromine water.

To compare the reactivity’s of an alkane and an alkene, a bromine test needs to be completed. The alkane and alkene used should be a cyclohexane and cyclohexene because they exist both as liquids at a room temperature of 25⁰C and hence is easier to be handled rather than a gas. They also only vary by a double bond so other variables wouldn’t influence the results.

The chemical used should be bromine water and should only react with a double bond, not the single bonds. Around 2ml of bromine water should be added to a test tube each containing cyclohexane and cyclohexene and should be gently shaken. All variables such as volume and temperature should be kept constant.

The two test tubes both contained two layers; one a lower aqueous state layer and the other, an upper organic layer. However the hexane had its aqueous later as yellow-orange where-as the cyclohexene layer turned fully colourless. This compared the reactivity of the alkenes with its corresponding alkane as the change of colour was almost instantaneous with the hexane but the hexane turned orange-brown as the experiment didn’t occur with its UV ray catalyst. Hence, the decolourisation of either chemical indicated the presence of unsaturated hydrocarbons and hence, the chemical was identified as either an alkene or alkane.

Background information:

- Bromine water has a distinctive brown colour - Alkenes react spontaneously with bromine water due to their unsaturated natureo It breaks open the alkenes’ double bond and includes bromine in its structure (addition reaction) forming an alkane o Therefore, the alkene coming in contact with the bromine water causes it to decolourise and hence becomes colourless- Alkanes don’t react spontaneously with bromine water due to their saturated nature. o Bromine is a non-polar molecule and therefore dissolves more readily in a non-polar alkane than in polar water. o Hence, when alkanes come into contact with bromine water, there are two visible separate layers having no reaction o If placed in UV light, a substitution reaction can occur where the colour of the alkane becomes colourless over a period of time while the bromine substance keeps a great part of its original colour.

Write the equations of each chemical change:

Analyse information from secondary sources such as computer simulations, molecular model kits or multimedia resources to model the polymerisation process.

The use of secondary sources such as computer simulations and molecular modelling kits is appropriate in the study of polymerisation.

Computer simulation allows one to see the relationship between…- Structure of monomer- Structure of the polymer- Where bonds are broken and formed- Showing spatial relationships of various atoms and bonds- Allow bond angles to be accurately portrayed and the molecules to be rotated and altered quickly

Molecule models…- Allow a 3D understanding of the shapes of the molecules, which cannot be gained from drawings.

- Allow rotation about the bonds- It is important to understand these relationships by using models, as it is not possible to view the molecules directly, and bonding is its integral to many properties of the molecules

Models can be used to show how monomers form a polymer. It simulates the movement of the electrons during bond breakage and formations as well as the movement of protons during neutralisation reactions. This is distinguished between the ionisation of strong and weak acids. Models give an indication of which atoms are joined to which and the general shape of the molecule is understood in helping in the understanding of isomers. They are used to visualise what is happening in the atomic and subatomic levels.

Models however aren’t to scale and so they are used for only the general idea, not accurately measured information.

Some scientists research the extraction of materials from biomass to reduce our dependence on fossil fuels.

Discuss the need for alternative sources of the compounds presently obtained from the petrochemical industry.

Petrochemicals like ethylene come from crude oils. Currently, there is plenty of petroleum to meet the needs for production sources of plastic production but it might only last a couple of decades if simultaneously burnt and used for plastic production. - Petrochemicals/crude oils are chemicals made from compounds in petroleum or natural gas. Currently, Australia has petroleum reserves that will last about ten years and natural gas reserves that will last about 100 years. Fossil fuels take billions of years to accumulate, in comparison.- 95% of fossil fuels are burnt as a source of energy and once burnt; it is no longer available – non-renewable source. - Less than 5% of the fuels are used for plastic production and only a small percentage of this plastic is recycled. - If energy and material needs are to be met in future, or kept consistent, alternative sources will be needed as fossil fuels are most likely to run out- Using fossil fuels does have a disadvantage despite its great use for a source of energy. o An increase in carbon dioxide levels in the atmosphere leading to global warming. – Greenhouse Effecto This impacts the sustainability of agriculture, and the survival of many species of plants and animals. - Fossil fuels coming from underground and dug out has caused a permanent damage to the environment because of its practise for millions of years.

Many scientists have tried different approaches to solving these problems. The complexity and expense of the alternatives has made them uneconomical and have failed to become widely adopted. Though, rising world oil prices are slowly changing the economics of the situation, and soon these alternatives may become not only viable but mainstream!

Monomer Polymer

Explain what is meant by a condensation polymer.

Polymers occurring in nature are starch, cellulose, glycogen, proteins, DNA, RNA, etc. These are examples of biopolymers – a naturally occurring polymer generated using natural resources. The processes by which these are formed are called condensation polymerisations. It is a polymer that is formed by the joining of monomers that eliminate small molecules such a water (through the formation of monomers and eliminates two hydrogen atoms and an oxygen atom). Hence, condensation polymers do not contain all the atoms initially present in the monomer, therefore different to the additional polymers.

Condensation polymerisation:The process involves:- Requires two different monomers- Each monomer has two identical groups/functional groups- Involves reaction between functional groups of each monomer- Releases a small molecule, e.g. water. This has now been extended to a small molecule. They require two different monomers.

Describe the reaction involved when a condensation polymer is formed.

Condensation polymerisations are used to make polyesters, nylon and polyurethane. Key features of condensation polymerisation are that any two molecular species can react, chains start short and steadily grow, most monomers go early in the reaction, and reactions are relatively slow and generate little heat. Nylon is used for fishing lines, toothbrushes, stockings, and raincoats.

The most important condensation polymer, PET participates in this reaction. PET’s are used for plastics, Dacron’s and other fabrics.

**Draw the PET polymer showing the ester linkage**

Describe the structure of cellulose and identify it as an example of a condensation polymer found as a major component of biomass.

All organic materials produced by living organisms such as plants, etc., have been compressed through time and used to create crude oils. Cellulose and Starch are biopolymers formed by condensation polymerisation. They are used in nature as starch is used as food storage in plants and cellulose is used as protective fibres in the cell wall. Cellulose is more recently converted into celluloid (films).

A biomass is the mass of living things in an environment. It is created by photosynthesis and is essential for biomass. This is because photosynthesis provides glucose for plants – the producers in a food chain. Using biomass as a fuel has many current problems.- It is too costly to make fuels out of living things in comparison to fossil fuels- Biomass fuels costs more than fossil fuels - There isn’t enough arable, fertile land to grow enough crops.

Cellulose is a major component of a plant and is the most abundant molecule in living tissues making around 50% of total organic carbon in biosphere. Cellulose is a flat, straight, and rigid molecule.

- Most dry plant material consists of up to 50% cellulose. Approximately, 5x1011 tonnes of cellulose are produced each year by land plants. - Cellulose is made up of many units of the sugar glucose covalently bound together – i.e. it is a polymer of glucose units. - Glucose is the same monomer that goes to make up starch and glycogen – the energy storage material we have in our livers. Though the monomers are the same, the way they are arranged is different – this is why they have different functions in a cell.

Formation of cellulose:- The formula for glucose is HO-C6H12O6 – OH. The HO-OH group eliminates two hydrogen and one oxygen atoms and hence eliminates a water molecule with one oxygen remaining. - Cellulose contains β-glucose monomers with two hydroxide groups with one pointing downwards and the other upwards. These monomers join to form a condensing polymer of cellulose. - The β-glucose aligns themselves that form a linear structure. As the glucose condense, the hydroxyl group on one side of the monomer is removed and the hydrogen from the other hydroxyl group is removed to form the eliminated molecule – water.

Formation of Starch:- α-glucose has both hydroxyl groups (OH) pointing downwards and these monomers form a condensation polymer which we know as starch.

**Draw the formation of Cellulose and its components and the formation of Starch and its components:**

Identify that cellulose contains the basic carbon-chain structures needed to build petrochemicals and discuss its potential as a raw material.