IGCSE Chemistry CIE Organic Chemistry PDF

Head to savemyexams.co.uk for more awesome resources YOUR NOTES IGCSE Chemistry CIE...

Head to savemyexams.co.uk for more awesome resources YOUR NOTES IGCSE Chemistry CIE  11. Organic Chemistry CONTENTS 11.1 Formulae, Functional Groups & Terminology 11.1.1 Organic Formulae 11.1.2 Homologous Series 11.1.3 Saturated & Unsaturated Compounds 11.1.4 Naming Organic Compounds 11.2 Organic Families 11.2.1 Fossil Fuels 11.2.2 Alkanes 11.2.3 Alkenes 11.2.4 Addition Reactions 11.2.5 Alcohols 11.2.6 Carboxylic Acids 11.2.7 Ethanoic Acid & Esterification Reactions 11.3 Polymers 11.3.1 Polymers 11.3.2 Addition & Condensation Polymers 11.3.3 Plastics & their Disposal 11.3.4 Proteins Page 1 of 48 © 2015-2021 Save My Exams, Ltd. · Revision Notes, Topic Questions, Past Papers  Head to savemyexams.co.uk for more awesome resources 11.1 Formulae, Functional Groups & Terminology YOUR NOTES  11.1.1 Organic Formulae Displayed Formulae Organic Chemistry is the scientific study of the structure, properties, and reactions of organic compounds. Organic compounds are those which contain carbon For conventional reasons metal carbonates, carbon dioxide and carbon monoxide are not included in organic compounds Many of the structures you will be drawing are hydrocarbons A hydrocarbon is a compound that contains only hydrogen and carbon atoms Organic compounds can be represented in a number of ways: Displayed Formulae General Formulae Structural Formulae The displayed formula shows the spatial arrangement of all the atoms and bonds in a molecule For example: This displayed formula tells us several things about the compound It has 5 carbon atoms It has 12 hydrogen atoms It has only single bonds Page 2 of 48 © 2015-2021 Save My Exams, Ltd. · Revision Notes, Topic Questions, Past Papers  Head to savemyexams.co.uk for more awesome resources Structural Formulae YOUR NOTES EXTENDED  In structural formulae, enough information is shown to make the structure clear, but most of the actual covalent bonds are omitted Only important bonds are always shown, such as double and triple bonds Identical groups can be bracketed together Side groups are also shown using brackets Straight chain alkanes are shown as follows: Structural Isomers Structural isomers are compounds that have the same molecular formula but different structural formulae The molecular formula is the actual number of atoms of each element in a compound Compounds with the same molecular formula can have different structural formulae due to the different arrangement of their atoms in space Two examples of structural isomers are shown below Table showing Structural Isomerism in C 4H10 Table showing Structural Isomerism in C 4H8 Page 3 of 48 © 2015-2021 Save My Exams, Ltd. · Revision Notes, Topic Questions, Past Papers  Head to savemyexams.co.uk for more awesome resources YOUR NOTES   Exam Tip Remember: Only double and triple bonds are shown in structural formulae. Page 4 of 48 © 2015-2021 Save My Exams, Ltd. · Revision Notes, Topic Questions, Past Papers  Head to savemyexams.co.uk for more awesome resources 11.1.2 Homologous Series YOUR NOTES  Homologous Series This is a series or family of organic compounds that have similar features and chemical properties due to them having the same functional group The functional group is a group of atoms which are bonded in a specific arrangement that is responsible for the characteristic reactions of each member of a homologous series Table of Compounds & their Functional Groups  Exam Tip Make sure you can identify the functional group for each homologous series. Page 5 of 48 © 2015-2021 Save My Exams, Ltd. · Revision Notes, Topic Questions, Past Papers  Head to savemyexams.co.uk for more awesome resources General Formulae YOUR NOTES General Formulae  This type of formula tells you the composition of any member of a whole homologous series of organic compound For example, all of the alkanes have the general formula CnH2n+2, where n represents the number of carbon atoms This tells you that however many carbon atoms there are in the alkane, doubling this number and adding two will give you the number of hydrogen atoms present in the alkane General formulae can be used to work out the formula of a compound from different homologous series if the number of carbon atoms present is known General Formula of Common Homologous Series Homologous Series General Formula Alkanes CnH2n+2 Alkenes CnH2n Alcohols CnH2n+1OH Carboxylic Acids CnH2n+1COOH  Worked Example What is the formula of an alcohol that contains 5 carbon atoms? Answer Number of carbons = 5 Number of hydrogens (excluding in the functional group) = 2 x 5 + 1 = 11 Formula = C5H11OH  Worked Example A compound has the formula C 12H24. To which homologous series does this compound belong to? Answer There are 12 carbon atoms, so n = 12 There are twice the number of hydrogen atoms than carbon atoms = 2n Therefore the general formula of the compound is CnH2n which means this compound is an alkene Page 6 of 48 © 2015-2021 Save My Exams, Ltd. · Revision Notes, Topic Questions, Past Papers  Head to savemyexams.co.uk for more awesome resources General Characteristic of Homologous Series YOUR NOTES EXTENDED  Characteristics of a Homologous Series All members of a homologous series have: The same general formula Same functional group Similar chemical properties Gradation in their physical properties, such as melting and boiling point The difference in the molecular formula between one member and the next is CH2 These characteristics are shown below for ethanol and propanol, which belong to homologous series, alcohols Table of Characteristics of Ethanol and Propanol  Exam Tip Make sure you learn the general formula for each homologous series. Page 7 of 48 © 2015-2021 Save My Exams, Ltd. · Revision Notes, Topic Questions, Past Papers  Head to savemyexams.co.uk for more awesome resources 11.1.3 Saturated & Unsaturated Compounds YOUR NOTES  Saturated & Unsaturated Compounds Saturated compounds have molecules in which all carbon-carbon bonds are single bonds Examples of compounds that are saturated are alkanes Alkanes are saturated hydrocarbons with the general formula CnH2n+2 Alkanes contain only carbon-carbon single bonds so are saturated Unsaturated compounds consist of molecules in which one or more carbon- carbon bonds are not single bonds They contain carbon-carbon double bonds (C=C) Examples of compounds that are unsaturated are alkenes. Alkenes are unsaturated hydrocarbons with the general formula is C nH2n The presence of the double bond, C=C, means they can make more bonds with other atoms by opening up the C=C bond and allowing incoming atoms to form another single bond with each carbon atom of the functional group Each of these carbon atoms now forms 4 single bonds instead of 1 double and 2 single bonds Alkenes contain one carbon-carbon double bond so are unsaturated  Exam Tip Remember: Saturated compounds have Single bonds only. Unsaturated compounds have doUble bonds Page 8 of 48 © 2015-2021 Save My Exams, Ltd. · Revision Notes, Topic Questions, Past Papers  Head to savemyexams.co.uk for more awesome resources 11.1.4 Naming Organic Compounds YOUR NOTES  Naming Organic Compounds The names of organic compounds have two parts: the prefix (or stem) and the end part (or suffix) The prefix tells you how many carbon atoms are present in the longest continuous chain in the compound The suffix tells you what functional group is on the compound Structures of organic compounds Page 9 of 48 © 2015-2021 Save My Exams, Ltd. · Revision Notes, Topic Questions, Past Papers  Head to savemyexams.co.uk for more awesome resources YOUR NOTES  Exam Tip Make sure you can draw and name the structures given above.  Page 10 of 48 © 2015-2021 Save My Exams, Ltd. · Revision Notes, Topic Questions, Past Papers  Head to savemyexams.co.uk for more awesome resources Further Naming of Organic Compounds YOUR NOTES EXTENDED  Further Rules for Naming Compounds When there is more than one carbon atom where a functional group can be located it is important to distinguish exactly which carbon the functional group is on Each carbon is numbered and these numbers are used to describe where the functional group is For example: Propan-1-ol is alcohol with an -OH functional group The 2 in the name indicates that the -OH group is located on the second carbon atom In propan-1-ol the -OH group is located on the first carbon atom Alkanes Alkenes Page 11 of 48 © 2015-2021 Save My Exams, Ltd. · Revision Notes, Topic Questions, Past Papers  Head to savemyexams.co.uk for more awesome resources YOUR NOTES  Alcohols Page 12 of 48 © 2015-2021 Save My Exams, Ltd. · Revision Notes, Topic Questions, Past Papers  Head to savemyexams.co.uk for more awesome resources YOUR NOTES  Carboxylic acids Page 13 of 48 © 2015-2021 Save My Exams, Ltd. · Revision Notes, Topic Questions, Past Papers  Head to savemyexams.co.uk for more awesome resources YOUR NOTES  Esters Page 14 of 48 © 2015-2021 Save My Exams, Ltd. · Revision Notes, Topic Questions, Past Papers  Head to savemyexams.co.uk for more awesome resources YOUR NOTES  Page 15 of 48 © 2015-2021 Save My Exams, Ltd. · Revision Notes, Topic Questions, Past Papers  Head to savemyexams.co.uk for more awesome resources 11.2 Organic Families YOUR NOTES  11.2.1 Fossil Fuels Common Fossil Fuels A fuel is a substance which when burned, releases heat energy This heat can be transferred into electricity, which we use in our daily lives Most common fossil fuels include coal, natural gas and hydrocarbons such as methane and propane which are obtained from crude oil Hydrocarbons are made from hydrogen and carbon atoms only The main constituent of natural gas is methane, CH4 Page 16 of 48 © 2015-2021 Save My Exams, Ltd. · Revision Notes, Topic Questions, Past Papers  Head to savemyexams.co.uk for more awesome resources Petroleum & Fractional Distillation YOUR NOTES Petroleum  Petroleum is also called crude oil and is a complex mixture of hydrocarbons which also contains natural gas It is a thick, sticky, black liquid that is found under porous rock (under the ground and under the sea) Diagram showing crude oil under the sea Petroleum itself as a mixture isn't very useful but each component part of the mixture, called a fraction, is useful and each fraction has different applications The fractions in petroleum are separated from each other in a process called fractional distillation The molecules in each fraction have similar properties and boiling points, which depend on the number of carbon atoms in the chain Page 17 of 48 © 2015-2021 Save My Exams, Ltd. · Revision Notes, Topic Questions, Past Papers  Head to savemyexams.co.uk for more awesome resources The boiling point and viscosity of each fraction increase as the carbon chain gets YOUR NOTES longer  Fractional Distillation Diagram showing the process of fractional distillation Fractional distillation is carried out in a fractionating column The fractionating column is hot at the bottom and cools at the top Crude oil enters the fractionating column and is heated so vapours rise Vapours of hydrocarbons with very high boiling points will immediately turn into liquid and are tapped off at the bottom of the column Vapours of hydrocarbons with low boiling points will rise up the column and condense at the top to be tapped off The different fractions condense at different heights according to their boiling points and are tapped off as liquids. The fractions containing smaller hydrocarbons are collected at the top of the fractionating column as gases The fractions containing bigger hydrocarbons are collected at the lower sections of the fractionating column Properties of Fractions Page 18 of 48 © 2015-2021 Save My Exams, Ltd. · Revision Notes, Topic Questions, Past Papers  Head to savemyexams.co.uk for more awesome resources Viscosity YOUR NOTES This refers to the ease of flow of a liquid.  High viscosity liquids are thick and flow less easily. If the number of carbon atoms increases, the attraction between the hydrocarbon molecules also increases which results in the liquid becoming more viscous with the increasing length of the hydrocarbon chain. The liquid flows less easily with increasing molecular mass Colour As carbon chain length increases the colour of the liquid gets darker as it gets thicker and more viscous Melting point/boiling point As the molecules get larger, the intermolecular attraction becomes greater. More heat is needed to separate the molecules. With increasing molecular size there is an increase in boiling point Volatility Volatility refers to the tendency of a substance to vaporise. With increasing molecular size hydrocarbon liquids become less volatile. This is because the attraction between the molecules increases with increasing molecular size Uses of Fractions Refinery gas: heating and cooking Gasoline: fuel for cars (petrol) Naphtha: raw product for producing chemicals Kerosene: for making jet fuel (paraffin) Diesel: fuel for diesel engines (gas oil) Fuel oil: fuel for ships and for home heating Lubricating oil: for lubricants, polishes, waxes Bitumen: for surfacing roads Trends in Properties Page 19 of 48 © 2015-2021 Save My Exams, Ltd. · Revision Notes, Topic Questions, Past Papers  Head to savemyexams.co.uk for more awesome resources YOUR NOTES   Exam Tip When defining a hydrocarbon, ensure you say that it has hydrogen and carbon atoms only. Page 20 of 48 © 2015-2021 Save My Exams, Ltd. · Revision Notes, Topic Questions, Past Papers  Head to savemyexams.co.uk for more awesome resources 11.2.2 Alkanes YOUR NOTES  Alkanes: Properties & Bonding Alkanes are a group of saturated hydrocarbons The term saturated means that they only have single carbon-carbon bonds, there are no double bonds The general formula of the alkanes is CnH2n+2 They are colourless compounds which have a gradual change in their physical properties as the number of carbon atoms in the chain increases Alkanes are generally unreactive compounds but they do undergo combustion reactions, can be cracked into smaller molecules and can react with halogens in the presence of light in substitution reactions Methane is an alkane and is the major component of natural gas Methane undergoes complete combustion forming carbon dioxide and water: CH4 (g) + 2O2 (g) → CO2 (g) + 2H2O (l) This Table shows the Displayed Formula of the First Four Members of the Alkane Homologous Series Page 21 of 48 © 2015-2021 Save My Exams, Ltd. · Revision Notes, Topic Questions, Past Papers  Head to savemyexams.co.uk for more awesome resources Substitution Reaction of Alkanes with Halogens YOUR NOTES Extended  In a substitution reaction, one atom (or group of atoms) is swapped with another atom (or group of atoms) Alkanes undergo a substitution reaction with halogens in the presence of ultraviolet radiation (sunlight is a source of UV radiation) This is called a photochemical reaction The UV light provides the activation energy, Ea, for the reaction A hydrogen atom is replaced with the halogen atom More than one hydrogen atom can be substituted depending on the amount of ultraviolet radiation there is In the presence of ultraviolet (UV) radiation, methane reacts with chlorine to form chloromethane and hydrogen chloride  Exam Tip You need to be able to draw the displayed and structural formulae of the products formed when one halogen atom replaces a hydrogen (also known as monosubstitution) Page 22 of 48 © 2015-2021 Save My Exams, Ltd. · Revision Notes, Topic Questions, Past Papers  Head to savemyexams.co.uk for more awesome resources 11.2.3 Alkenes YOUR NOTES  Catalytic Cracking Alkenes are unsaturated hydrocarbons with carbon-carbon double bonds (C=C) Their general formula is CnH2n The presence of the double bond, C=C, means they can make more bonds with other atoms by opening up the C=C bond and allowing incoming atoms to form another single bond with each carbon atom of the functional group Each of these carbon atoms now forms 4 single bonds instead of 1 double and 2 single bonds This makes them much more reactive than alkanes The displayed formula of the first three alkenes Manufacture of Alkenes Although there is use for each fraction obtained from the fractional distillation of crude oil, the amount of longer chain hydrocarbons produced is far greater than needed These long chain hydrocarbon molecules are further processed to produce other products A process called catalytic cracking is used to convert longer-chain molecules into short-chain and more useful hydrocarbons Shorter chain alkanes, alkenes and hydrogen are produced from the cracking of longer chain alkanes Alkenes can be used to make polymers and the hydrogen used to make ammonia Kerosene and diesel oil are often cracked to produce petrol, other alkenes and hydrogen Cracking involves heating the hydrocarbon molecules to around 600 – 700°C to vaporise them The vapours then pass over a hot powdered catalyst of alumina or silica This process breaks covalent bonds in the molecules as they come into contact with the surface of the catalyst, causing thermal decomposition reactions The molecules are broken up in a random way which produces a mixture of smaller alkanes and alkenes Hydrogen and a higher proportion of alkenes are formed at higher temperatures and higher pressure Page 23 of 48 © 2015-2021 Save My Exams, Ltd. · Revision Notes, Topic Questions, Past Papers  Head to savemyexams.co.uk for more awesome resources YOUR NOTES  The 10 carbon molecule decane is catalytically cracked to produce octane for petrol and ethene for ethanol  Exam Tip When describing what happens to bromine water in an alkene ensure you say colourless, and not clear. Page 24 of 48 © 2015-2021 Save My Exams, Ltd. · Revision Notes, Topic Questions, Past Papers  Head to savemyexams.co.uk for more awesome resources Distinguishing from Alkanes YOUR NOTES Distinguishing Between Alkanes & Alkenes  Alkanes and alkenes have different molecular structures All alkanes are saturated and alkenes are unsaturated The presence of the C=C double bond allows alkenes to react in ways that alkanes cannot This allows us to tell alkenes apart from alkanes using a simple chemical test using bromine water Bromine water is an orange coloured solution of bromine When bromine water is shaken with an alkane, it will remain as an orange solution as alkanes do not have double carbon bonds (C=C) so the bromine remains in solution When bromine water is shaken with an alkene, the alkene will decolourise the bromine water and turn colourless as alkenes do have double carbon bonds (C=C) The bromine atoms add across the C=C double bond hence the solution no longer contains the orange coloured bromine This reaction between alkenes and bromine is called an addition reaction Page 25 of 48 © 2015-2021 Save My Exams, Ltd. · Revision Notes, Topic Questions, Past Papers  Head to savemyexams.co.uk for more awesome resources YOUR NOTES  Each carbon atom of the double bond accepts a bromine atom, causing the bromine solution to lose its colour  Exam Tip When describing what happens to bromine water in an alkene ensure you say colourless, and not clear. Page 26 of 48 © 2015-2021 Save My Exams, Ltd. · Revision Notes, Topic Questions, Past Papers  Head to savemyexams.co.uk for more awesome resources 11.2.4 Addition Reactions YOUR NOTES  Addition Reactions EXTENDED Alkenes undergo addition reactions in which atoms of a simple molecule add across the C=C double bond The reaction between bromine and ethene is an example of an addition reaction Bromine atoms add across the C=C in the addition reaction of ethene and bromine Alkenes also undergo addition reactions with hydrogen in which an alkane is formed These are hydrogenation reactions and occur at 150ºC using a nickel catalyst Hydrogenation reactions are used to manufacture margarine from vegetable oils Vegetable oils are polyunsaturated molecules which are partially hydrogenated to increase the Mr and turn the oils into solid fats Hydrogen atoms add across the C=C in the hydrogenation of ethene to produce an alkane Alkenes also undergo addition reactions with steam in which an alcohol is formed. Page 27 of 48 © 2015-2021 Save My Exams, Ltd. · Revision Notes, Topic Questions, Past Papers  Head to savemyexams.co.uk for more awesome resources Since water is being added to the molecule it is also called a hydration reaction YOUR NOTES The reaction is very important industrially for the production of alcohols and it  occurs using the following conditions: Temperature of around 300ºC Pressure of 60 - 70 atm Concentrated phosphoric acid catalyst A water molecule adds across the C=C in the hydration of ethene to produce ethanol  Exam Tip You need to be able to draw the displayed formulae of the products of alkenes with water, hydrogen and bromine. Page 28 of 48 © 2015-2021 Save My Exams, Ltd. · Revision Notes, Topic Questions, Past Papers  Head to savemyexams.co.uk for more awesome resources 11.2.5 Alcohols YOUR NOTES  Alcohols All alcohols contain the hydroxyl (-OH) functional group which is the part of alcohol molecules that is responsible for their characteristic reactions Alcohols are a homologous series of compounds that have the general formula C nH2n+1OH They differ by one -CH2 in the molecular formulae from one member to the next Diagram showing the first three alcohols Ethanol (C2H5OH) is one of the most important alcohols It is the type of alcohol found in alcoholic drinks such as wine and beer It is also used as fuel for cars and as a solvent Alcohols burn in excess oxygen and produce CO2 and H2O Ethanol undergoes complete combustion: CH3CH2OH (l) + 3O2 (g) → 2CO2 (g) + 3H20 (l) The Manufacture of Ethanol There are two methods used to manufacture ethanol: The hydration of ethene with steam The fermentation of glucose Both methods have advantages and disadvantages which are considered Hydration of ethene A mixture of ethene and steam is passed over a hot catalyst of phosphoric acid at a temperature of approximately 300 °C The pressure used is 60 atmospheres (6000kPa) The gaseous ethanol is then condensed into a liquid for use Page 29 of 48 © 2015-2021 Save My Exams, Ltd. · Revision Notes, Topic Questions, Past Papers  Head to savemyexams.co.uk for more awesome resources YOUR NOTES  A water molecule adds across the C=C in the hydration of ethene to produce ethanol Fermentation of glucose Sugar or starch is dissolved in water and yeast is added The mixture is then fermented between 25 and 35 °C with the absence of oxygen for a few days Yeast contains enzymes that catalyse the break down of starch or sugar to glucose If the temperature is too low the reaction rate will be too slow and if it is too high the enzymes will become denatured The yeast respire anaerobically using the glucose to form ethanol and carbon dioxide: C6H12O6 → 2CO2 + 2C2H5OH The yeast are killed off once the concentration of alcohol reaches around 15%, hence the reaction vessel is emptied and the process is started again This is the reason that ethanol production by fermentation is a batch process  Exam Tip Make sure you learn the conditions for both hydration and fermentation. Page 30 of 48 © 2015-2021 Save My Exams, Ltd. · Revision Notes, Topic Questions, Past Papers  Head to savemyexams.co.uk for more awesome resources Comparing Methods of Ethanol Production YOUR NOTES Extended  Page 31 of 48 © 2015-2021 Save My Exams, Ltd. · Revision Notes, Topic Questions, Past Papers  Head to savemyexams.co.uk for more awesome resources 11.2.6 Carboxylic Acids YOUR NOTES  Carboxylic Acids The carboxylic acids behave like other acids They react with: metals to form a salt and hydrogen carbonates to form a salt, water and carbon dioxide gas They also take part in neutralisation reactions to produce salt and water Ethanoic acid (also called acetic acid ) is the acid used to make vinegar, which contains around 5% by volume ethanoic acid The salts formed by the reaction of carboxylic acids all end –anoate So methanoic acid forms a salt called methanoate, ethanoic a salt called ethanoate etc. In the reaction with metals, a metal salt and hydrogen gas are produced Example reactions of carboxylic acids The reaction of ethanoic acid with magnesium, forms the salt magnesium ethanoate , and hydrogen gas: 2CH3COOH + Mg → (CH3COO)2Mg + H2 In the reaction with hydroxides a salt and water are formed in a neutralisation reaction For example the reaction between potassium hydroxide and propanoic acid forms the salt potassium propanoate, and water: CH3CH2COOH + KOH → CH3CH2COOK + H2O In the reaction with carbonates a metal salt, water and carbon dioxide gas are produced For example the reaction between potassium carbonate and butanoic acid, the salt potassium butanoic acid is formed, with water and carbon dioxide 2CH3CH2CH2COOH + K2CO3 → 2CH3CH2CH2COOK + H2O + CO2  Exam Tip You need to be able to name and give the formulae of the salts produced in these reactions. Page 32 of 48 © 2015-2021 Save My Exams, Ltd. · Revision Notes, Topic Questions, Past Papers  Head to savemyexams.co.uk for more awesome resources 11.2.7 Ethanoic Acid & Esterification Reactions YOUR NOTES  Formation of Ethanoic Acid EXTENDED Making Carboxylic Acids Two methods used to make carboxylic acids are: Oxidation by fermentation Using oxidising agents The microbial oxidation (fermentation) of ethanol will produce a weak solution of vinegar (ethanoic acid) This occurs when a bottle of wine is opened as bacteria in the air (acetobacter) will use atmospheric oxygen from air to oxidise the ethanol in the wine C2H5OH (aq) + O2 (g) → CH3COOH (aq)+ H2O (l) The acidic, vinegary taste of wine which has been left open for several days is due to the presence of ethanoic acid Alternatively, oxidising agent potassium manganate(VII) can be used This involves heating ethanol with acidified potassium manganate(VII) in the presence of an acid The heating is performed under reflux which involves heating the reaction mixture in a vessel with a condenser attached to the top The condenser prevents the volatile alcohol from escaping the reaction vessel as alcohols have low boiling points The equation for the reaction is: CH3CH2OH (aq) + [O] → CH3COOH (aq) + H2O (l) The solution will change from purple to colourless Page 33 of 48 © 2015-2021 Save My Exams, Ltd. · Revision Notes, Topic Questions, Past Papers  Head to savemyexams.co.uk for more awesome resources The oxidising agent is represented by the symbol for oxygen in square brackets YOUR NOTES  Diagram showing the experimental setup for the oxidation with KMnO4 using reflux apparatus Page 34 of 48 © 2015-2021 Save My Exams, Ltd. · Revision Notes, Topic Questions, Past Papers  Head to savemyexams.co.uk for more awesome resources Esterification YOUR NOTES EXTENDED  Alcohols and carboxylic acids react to make esters in esterification reactions Esters are compounds with the functional group R-COO-R Esters are sweet-smelling oily liquids used in food flavourings and perfumes Ethanoic acid will react with ethanol in the presence of concentrated sulfuric acid (catalyst) to form ethyl ethanoate: CH3COOH (aq) + C2H5OH (aq) ⇌ CH3COOC2H5 (aq) + H2O (l) Diagram showing the formation of ethyl ethanoate Naming Esters An ester is made from an alcohol and carboxylic acid The first part of the name indicates the length of the carbon chain in the alcohol, and it ends with the letters ‘- yl’ Page 35 of 48 © 2015-2021 Save My Exams, Ltd. · Revision Notes, Topic Questions, Past Papers  Head to savemyexams.co.uk for more awesome resources The second part of the name indicates the length of the carbon chain in the YOUR NOTES carboxylic acid, and it ends with the letters ‘- oate’  E.g. the ester formed from pentanol and butanoic acid is called pentyl butanoate Diagram showing the origin of each carbon chain in ester; this ester is ethyl butanoate Table showing the Formation of Esters Page 36 of 48 © 2015-2021 Save My Exams, Ltd. · Revision Notes, Topic Questions, Past Papers  Head to savemyexams.co.uk for more awesome resources YOUR NOTES  Page 37 of 48 © 2015-2021 Save My Exams, Ltd. · Revision Notes, Topic Questions, Past Papers  Head to savemyexams.co.uk for more awesome resources 11.3 Polymers YOUR NOTES  11.3.1 Polymers Polymers: The Basics Polymers are large molecules built by linking 50 or more smaller molecules called monomers Each repeat unit is connected to the adjacent units via covalent bonds Some polymers contain just one type of unit Examples include poly(ethene) and poly(chloroethene), commonly known as PVC Others contain two or more different types of monomer units and which are called copolymers Examples include nylon and biological proteins Different linkages also exist, depending on the monomers and the type of polymerisation Examples of linkages are covalent bonds, amide links and ester links Diagram showing how lots of monomers bond together to form a polymer Page 38 of 48 © 2015-2021 Save My Exams, Ltd. · Revision Notes, Topic Questions, Past Papers  Head to savemyexams.co.uk for more awesome resources Poly(ethene) is formed by the addition polymerisation of ethene monomers YOUR NOTES Addition polymerisation involves the addition of many monomers to make a long  chained polymer In this case, many ethene monomers join together due to the carbon carbon double bond breaking Poly(ethene) is formed by addition polymerisation using ethene monomers Page 39 of 48 © 2015-2021 Save My Exams, Ltd. · Revision Notes, Topic Questions, Past Papers  Head to savemyexams.co.uk for more awesome resources 11.3.2 Addition & Condensation Polymers YOUR NOTES  Addition Polymers EXTENDED Addition polymers are formed by the joining up of many monomers and only occur in monomers that contain C=C bonds One of the bonds in each C=C bond breaks and forms a bond with the adjacent monomer with the polymer being formed containing single bonds only Many polymers can be made by the addition of alkene monomers Others are made from alkene monomers with different atoms attached to the monomer such as chlorine or a hydroxyl group The name of the polymer is deduced by putting the name of the monomer in brackets and adding poly- as the prefix For example if propene is the alkene monomer used, then the name is poly(propene) Poly(ethene) is formed by the addition polymerisation of ethene monomers Deducing the polymer from the monomer Polymer molecules are very large compared with most other molecule Repeat units are used when displaying the formula To draw a repeat unit, change the double bond in the monomer to a single bond in the repeat unit Add a bond to each end of the repeat unit The bonds on either side of the polymer must extend outside the brackets (these are called extension or continuation bonds) A small subscript n is written on the bottom right hand side to indicate a large number of repeat units Add on the rest of the groups in the same order that they surrounded the double bond in the monomer Page 40 of 48 © 2015-2021 Save My Exams, Ltd. · Revision Notes, Topic Questions, Past Papers  Head to savemyexams.co.uk for more awesome resources YOUR NOTES  Examples of addition polymerisation: polythene and PVC Deducing the monomer from the polymer Identify the repeating unit in the polymer Change the single bond in the repeat unit to a double bond in the monomer Remove the bond from each end of the repeat unit Diagram showing the monomer from the repeat unit of an addition polymer (polychloroethene)  Exam Tip You should be able to draw the box diagrams representing polymers where each box represents a part of the repeating hydrocarbon chain. The functional groups on the monomers and the link formed in the polymers are the important parts and must be clearly drawn. Page 41 of 48 © 2015-2021 Save My Exams, Ltd. · Revision Notes, Topic Questions, Past Papers  Head to savemyexams.co.uk for more awesome resources Condensation Polymers YOUR NOTES EXTENDED  Condensation polymers are formed when two different monomers are linked together with the removal of a small molecule, usually water This is a key difference between condensation polymers and addition polymers: Addition polymerisation forms the polymer molecule only Condensation polymerisation forms the polymer molecule and one water molecule per linkage The monomers have two functional groups present, one on each end The functional groups at the ends of one monomer react with the functional group on the end of the other monomer, in so doing creating long chains of alternating monomers, forming the polymer Hydrolysing (adding water) to the compound in acidic conditions usually reverses the reaction and produces the monomers by rupturing the peptide link Forming Nylon Nylon is a polyamide made from dicarboxylic acid monomers (a carboxylic with a -COOH group at either end) and diamines (an amine with an -NH2 group at either end) Each -COOH group reacts with another -NH2 group on another monomer An amide linkage is formed with the subsequent loss of one water molecule per link The condensation reaction in which the polyamide, nylon is produced The structure of nylon can be represented by drawing out the polymer using boxes to represent the carbon chains Page 42 of 48 © 2015-2021 Save My Exams, Ltd. · Revision Notes, Topic Questions, Past Papers  Head to savemyexams.co.uk for more awesome resources YOUR NOTES  Diagram showing a section of nylon Forming Polyesters PET or polyethylene terephthalate to give its full name, is a polyester made from dicarboxylic acid monomers (a carboxylic with a -COOH group at either end) and diols (alcohol with an -OH group at either end) Each -COOH group reacts with another -OH group on another monomer An ester linkage is formed with the subsequent loss of one water molecule per link For every ester linkage formed in condensation polymerisation, one molecule of water is formed from the combination of a proton (H+) and a hydroxyl ion (OH–) PET is also used in synthetic fibres as is sold under the trade name of terylene The condensation reaction in which PET is produced The structure of PET can be represented by drawing out the polymer using boxes to represent the carbon chains This can be done for all polyesters Diagram showing a section of PET Page 43 of 48 © 2015-2021 Save My Exams, Ltd. · Revision Notes, Topic Questions, Past Papers  Head to savemyexams.co.uk for more awesome resources YOUR NOTES  Exam Tip You don't need to know the detailed chemical structure of PET, just the  symbolic drawing showing the alternating blocks and the linking ester group. Be careful not to exactly repeat the linking group in nylon or PET; the link alternates by reversing the order of the atoms, rather like a mirror image. Page 44 of 48 © 2015-2021 Save My Exams, Ltd. · Revision Notes, Topic Questions, Past Papers  Head to savemyexams.co.uk for more awesome resources 11.3.3 Plastics & their Disposal YOUR NOTES  Plastics & their Disposal Synthetic polymers are ones made in a factory, for example nylon, terylene and lycra Nylon is a polyamide used to produce clothing, fabrics, nets and ropes PET, also known as Terylene, is a polyester made from monomers which are joined together by ester links PET is used extensively in the textile industry and is often mixed with cotton to produce clothing Table showing Uses of Plastics Non-biodegradable plastics These are plastics which do not degrade over time or take a very long time to degrade, and cause significant pollution problems In particular plastic waste has been spilling over into the seas and oceans and is causing huge disruptions to marine life In landfills waste polymers take up valuable space as they are non-biodegradable so microorganisms cannot break them down. This causes the landfill sites to quickly fill up Polymers release a lot of heat energy when incinerated and produce carbon dioxide which is a greenhouse gas that contributes to climate change If incinerated by incomplete combustion, carbon monoxide will be produced which is a toxic gas that reduces the capacity of the blood to carry oxygen Polymers can be recycled but different polymers must be separated from each other which is a difficult and expensive process Page 45 of 48 © 2015-2021 Save My Exams, Ltd. · Revision Notes, Topic Questions, Past Papers  Head to savemyexams.co.uk for more awesome resources PET Re-polymerisation YOUR NOTES PET stands for polyethylene terephthalate, a common polymer used to make things  like plastic bottles It is a condensation polymer consisting of repeating ester units, so it is type of polyester, like terylene One of the problems with recycling polymers is that the condition needed to break them down, which are usually high temperatures and pressures, can degrade the monomers making them unusable for re-polymerisation PET is relatively easy to convert back into the monomers It can be depolymerised either using enzymes or by chemical methods Enzymes present in microbes breakdown the PET into the original monomers The same can be achieved using solvents a catalyst and mild heating The breakdown of PET into its two monomers takes place using enzymes or chemical catalysts and mild conditions The monomers are recovered and be be polymerised into new PET This saves on resources and energy, reducing the carbon footprint of the production process Page 46 of 48 © 2015-2021 Save My Exams, Ltd. · Revision Notes, Topic Questions, Past Papers  Head to savemyexams.co.uk for more awesome resources 11.3.4 Proteins YOUR NOTES  Proteins Extended Proteins are condensation polymers which are formed from amino acid monomers joined together by amide links (in proteins also known as a peptide link) similar to the structure in nylon The units in proteins are different however, consisting of amino acids Amino acids are small molecules containing NH2 and COOH functional groups General structure of an amino acid There are twenty common amino acids, each differing by their side chain, represented by R Proteins can contain between 60 and 600 of these amino acids in different orders These are the monomers which polymerise to form the protein Page 47 of 48 © 2015-2021 Save My Exams, Ltd. · Revision Notes, Topic Questions, Past Papers  Head to savemyexams.co.uk for more awesome resources YOUR NOTES  Diagram showing condensation polymerisation to produce a protein The structure of proteins can be represented using the following diagram whereby the boxes represent the carbon chains Diagram showing a section of protein Page 48 of 48 © 2015-2021 Save My Exams, Ltd. · Revision Notes, Topic Questions, Past Papers