C10 Organic Reactions Student Booklet.pdf, Lecture notes of Chemistry

Download C10 Organic Reactions Student Booklet.pdf and more Lecture notes Chemistry in PDF only on Docsity! ™ Student Booklet C10 Organic Reactions Science Mastery Ark Curriculum+  You will know from previous units that there are many different types of molecules and the different structures of these molecules results in them having different properties. In the previous topic you learnt that hydrocarbons are organic compounds which contain only carbon and hydrogen atoms and how their structure allowed them to be used as fuels. In this unit you will be looking at more organic compounds and understanding how their functional group affects their characteristic reactions and properties. As you saw in the previous topic, organic chemistry is about carbon compounds (that’s compounds that contain carbon atoms). It is so important it forms its separate branch in chemistry. A great variety of carbon compounds are possible because carbon atoms can form chain and rings linked by C-C (carbon – carbon) bonds, sometimes hundreds of units long! There are different homologous series of organic compounds with different functional groups. The functional group gives these organic compounds their characteristic reactions. Chemists are able to take organic molecules and modify them in many ways to make new useful materials such as polymers, pharmaceuticals, perfumes, flavourings, dyes and detergents. It is important you can remember all about atomic structure (the structure of atoms). This is summarised here for you in case you don’t remember. https://www.bbc.co.uk/bitesize/guides/z3sg2nb/revision/3 You should know that there are different types of bonding, and what happens in each of these. You’ll find more information here: https://www.bbc.co.uk/bitesize/articles/z4yk8xs It is useful to know the typical properties for acids which can be found here: https://www.bbc.co.uk/bitesize/guides/zcjjfcw/revision/1 It is very important to remember all about hydrocarbons from the previous topic as this will be revisited along with other organic compounds in this topic. You’ll find some useful information here: https://www.bbc.co.uk/bitesize/guides/zshvw6f/revision/1 Structure determines properties C5, C9, C11, If you answered A, you have identified that the bond is between carbon and hydrogen atoms but have not identified the correct the type of bonding. If you answered B you have identified that it is a covalent bond but have not correctly identified which atoms this bond is between. If you answered A or B you should revise bonding here and complete the test at the end: https://www.bbc.co.uk/bitesize/guides/z6k6pbk/revision/2 If you answered A or B you have not understood the definition of a hydrocarbon. You should revise hydrocarbons here and complete the quiz at the end: https://www.bbc.co.uk/bitesize/guides/zdvqtfr/revision/1 If you answered B or C you have not correctly identified the molecular formulae of an alkane. In this topic it is important you can identify an organic compound from its molecular formula. You should revise alkanes using this link: https://www.bbc.co.uk/bitesize/guides/zvvwxnb/revision/2 If you answered B or C you have mistaken the correct functional groups, Alkenes have a functional group comprising a C=C bond and carboxylic acids have a functional group of - COOH. Read the following on alcohols (https://www.bbc.co.uk/bitesize/guides/z3v4xfr/revision/3) and draw a molecule of ethene, ethanol and ethanoic acid. Alkenes are saturated hydrocarbons, if you answered you have confused this with the definition of saturated hydrocarbons. A saturated hydrocarbon has all carbon-carbon bonds as single covalent bonds, this means they contain as many hydrogen atoms as possible per molecule. If you answered B or C draw one saturated molecule and one unsaturated molecule of any homologous series. If you chose A, you are confused about the homologous series – these are families of hydrocarbons which contain the same functional group. If you chose C, you have forgotten the prefixes which denote how many carbon atoms in a hydrocarbon. Read the following (https://www.mnemonic-device.com/chemistry/maggie-enjoys-pacifiers-bottles/) and come up with your own mnemonic device to remember the first 4 alkanes If you answered A or C, you have not understood how to represent the molecular formula of alkenes. To fix this, write the molecular formulae of the first three alkenes: ethene, propene and butene If you have answered A or B, you need to revisit Chemical changes, In this topic it is important you can predict reactions of acids with metals . You should revise this topic using this link: https://www.bbc.co.uk/bitesize/guides/zcjjfcw/revision/3 If you answered B or C this shows you have not understood what ‘structural formula’ means. You should revise the different ways of representing compound formulae and write the structural formulae of the first four alkanes: methane, ethane, propane and butane. If you answered A or C this shows you have not understood covalent bonding. You should revise the periodic table and covalent bonding and practice drawing the covalent structures CO2 and CH4. C B C A A A C C A B Reactions of alkenes Alkenes have the functional group (C=C). This characteristic enables them to take part in addition reactions. Reaction with halogens- a group 7 halogen is added to an alkene across the C=C bond for example; When chlorine is reacted with ethene this produces dichloroethane. Reaction with hydrogen – the addition of a hydrogen molecule across the alkenes double bond will form a saturated hydrocarbon. The reaction takes place at 60°C and in the presence of a nickel catalyst. For example, when hydrogen is reacted with propene, propane is formed. Reaction with water (steam) – the addition of steam to an alkene will produce an alcohol and is used in the production of ethanol for industrial use as a fuel or solvent. These hydration reactions require a temperature of 300°C and a catalyst. Alcohols Alcohols have the functional group -OH the first four members of the alcohols are: Methanol, ethanol, propanol and butanol. Carboxylic acids All carboxylic acids contain the functional group -COOH. The first four members of the carboxylic acids are methanoic acid, ethanoic acid, propanoic acid and butanoic acid. Knowledge Organiser Carboxylic acids have the typical properties for acids: • Dissolve in water to form an acidic solution with pH values less than 7 • React with metals to form a salt and hydrogen • React with bases to form a salt and water • React with carbonates to form a salt, water and carbon dioxide Esters Carboxylic acids react with alcohols to form esters. Esters are organic compounds with the functional group (- COO-). This reaction is reversible, and water is also formed. An acid catalyst (usually sulfuric acid) is used as well. The general formula is: alcohol + carboxylic acid → ester + water For example: ethanol + ethanoic acid → ethyl ethanote + water The esters formed have distinctive smells (many are sweet and fruity) this makes them ideal for perfumes and food colourings. Uses of the first four alcohols • Methanol is used as a chemical feedstock and it is toxic. • Ethanol is the alcohol present in alcoholic drinks. It is also used as a fuel and a solvent. • Propanol and butanol are both also used as solvents and fuels. Reactions of alcohols Combustion – alcohols undergo complete combustion to form carbon dioxide and water. However, when less oxygen is present incomplete combustion will occur to form water and either carbon monoxide or carbon. For example, ethanol used as a fuel ethanol + oxygen → carbon dioxide + water C2H5OH + 3O2 → 2CO2 + 3H2O Reaction with sodium – when sodium metal is added the ethanol, bubbles of hydrogen gas are produced, and the liquid contains sodium ethoxide. Methanol, propanol and butanol all undergo similar reactions. sodium + ethanol → sodium ethoxide + hydrogen 2Na + 2C2H5OH → 2C2H5ONa + H2 Oxidation – alcohols can be oxidised without combustion to produce carboxylic acids, using oxidising agents such as potassium dichromate (VI). For example: ethanol + oxidising agent → ethanoic acid + water HT: Carboxylic acids are weak acids compared to the strong acids shydrochloric acid and sulfuric acid. Acids show their acidic properties when dissolved in water, where they ionise to form H+ and the corresponding negative ions e.g. (HCl ionises to form H+ and Cl- ions). Carboxylic acids are weak acids because they do not completely ionise. For example: when ethanoic acid (CH3COOH is dissolved in water most molecules will stay as CH3COOH with only a few ionising. Therefore, the equilibrium is far to the left. The equation is shown below: CH3COOH(aq) ⇋ CH3COO-(aq) + H+(aq) 2. What is the molecular formula for butene? £ A. C4H8 £ B. C4H10 £ C. C4H6 3. Why are alkenes more reactive than alkanes? £ A. The double bond can open very easily. £ B. They are always smaller molecules. £ C. The bonds between the atoms are weaker in alkenes 1. What is produced when bromine reacts with ethene? £ A. Dibromoethene £ B. Dibromoethane £ C. Bromoethane If you answered A, you said that bromine and ethene react together to form dibromoethene. You should know that in this reaction bromine has been added across the double carbon bond in ethene, therefore it has been saturated and there will be no C=C bond. To fix it, draw the structure of ethane and ethene and explain how they different. If you answered B, you said that bromine and ethene react to form dibromoethane. This is indeed the compound produced. Well done! To further improve, explain why this is an example of an addition reaction and why alkenes can take part in addition reactions, but alkanes do not. If you answered C, you said that bromine and ethene react together to form bromoethane. You should know that bromine and other group 7 elements are diatomic meaning they exist as two atoms covalently bonded together, therefore during this reaction two bromine atoms would have reacted with ethene to form dibromoethane. To fix it, draw the displayed formula of the reaction between bromine and ethene to form dibromoethane. 1. Complete the table below by adding either the number of hydrogens, molecular formula or name of the alkenes. Complete the following questions. 2. Why does methene not exist? _______________________________________________________________________________________ _______________________________________________________________________________________ 3. Draw the two possible displayed formulae of butene. 4. Draw the displayed formula of the compound formed when propene reacts with hydrogen. 5. Explain why alkenes can take part in addition reactions but alkanes do not. _______________________________________________________________________________________ _______________________________________________________________________________________ _______________________________________________________________________________________ 6. Explain how you can test for the presence of an alkene? _______________________________________________________________________________________ _______________________________________________________________________________________ Lesson 2: Functional groups Starter 1. State the general formula of alkenes. 2. Draw the displayed formula of pentene which has 5 carbon atoms in its chain. 3. Explain why alkenes are not used as fuels but alkanes are. Foundation: Write the structural formula of butene. Stretch: Explain why alkenes can take part in addition reactions but alkanes cannot. Both alkanes and alkenes are made of only hydrogen and carbon atoms, however there are more homologous series of organic compounds which contain other types of atoms. Alcohols, carboxylic acids and esters all contain hydrogen, carbon and oxygen atoms. Alcohols Alcohols contain the functional group (-OH). The general formula for alcohols is CnH2n+1OH. The displayed formula of the first four alcohols methanol, ethanol, propanol and butanol is shown below. Carboxylic acids Carboxylic acids are another group of organic compounds with the most common being ethanoic acid which is the main acid in vinegar. They have the functional group (-COOH). Carboxylic acids are weak acids and have typical properties for an acid. The displayed formula of the first four carboxylic acids are shown below. Esters Esters contain the functional group (-COO-). They are closely related to carboxylic with the H atom from the -COOH functional being replaced with an alkyl group e.g. -CH3. They are formed when a carboxylic acid reacts with an alcohol. The structure of the ester ethyl ethanoate is shown on the right. Here you can find more information on functional groups: https://www.youtube.com/watch?v=nMTQKBn2Iss Lesson 3: Reactions and uses of alcohols Starter 1. State the general formula of alcohols 2. Describe how alcohols are formed 3. Describe uses of the first four alcohols Foundation: Write the structural formula of ethanol Stretch: Explain why alcohols are useful fuels Alcohols Alcohols contain the functional group (-OH). The general formula for alcohols is CnH2n+1OH. The displayed formula of the first four alcohols methanol, ethanol, propanol and butanol is shown below. Formation of alcohols 1. At high pressures, ethene gas reacts with steam to produce ethanol. Ethene is produced from the cracking of crude oil (finite resource) 2. Sugars found in plant material are fermented using yeast at 37°C, in anaerobic condition. • Plants are renewable Here you can find more information on Alcohols- 1. https://www.youtube.com/watch?v=LuicIvV3PjQ 2. https://www.youtube.com/watch?v=NzNlZZ1fKyM 3. https://www.youtube.com/watch?v=vVwLa1fRsVY 4. https://www.youtube.com/watch?v=TllSV8KNMzU 1. Which of the following is an alcohol? £ A. CH3COOH £ B. CH3CHO £ C. CH3CH2OH 3. What is the word equation for fermentation to produce ethanol? £ A. Glucose → ethanol + carbon dioxide £ B. Glucose + oxygen → ethanol + water £ C. Glucose + oxygen → ethanol + carbon dioxide 2. Identify the false statement £ A. Alcohols react with alkali metals £ B. Alcohols can be produced from plants £ C. Alcohols cannot be used as solvents If you answered A, you have incorrectly identified a carboxylic acid as an alcohol. Both compounds re organic compounds however carboxylic acids have the functional group -COOH. Alcohols have the – OH group. To fix it draw the displayed formula of the first 3 carboxylic acid compounds. If you answered B, you have incorrectly identified an aldehyde as an alcohol. Aldehydes and Alcohols are both organic compounds that differ in the functional group. To fix it refer to the section about functional groups on the knowledge organizer, revise and practice drawing structures of alcohols here: https://www.bbc.co.uk/bitesize/guides/z3v4xfr/revision/3 If you answered C, you said that compound C is an alcohol, this is correct, well done! To further improve read through the section here: https://www.bbc.co.uk/bitesize/guides/z3v4xfr/revision/3 and read further about how alcohols react. Here you can find more information on Alcohols- 1. https://www.youtube.com/watch?v=LuicIvV3PjQ 2. https://www.youtube.com/watch?v=NzNlZZ1fKyM 3. https://www.youtube.com/watch?v=TllSV8KNMzU https://www.youtube.com/watch?v=vVwLa1fRsVY Complete the table below Combustion of Alcohols Alcohols are flammable, they burn with a clean blue flame. The alcohols undergo complete combustion to form carbon dioxide and water. For example, ethanol is used as a fuel: ethanol + oxygen → carbon dioxide + water C2H5OH + 3O2 → 2CO2 + 3H2O Reaction with Sodium– Alcohols react with sodium to form (salts) sodium alkoxides and hydrogen For example: ethanol + sodium → sodium ethoxide + hydrogen. 2Na + 2C2H5OH → 2C2H5ONa + H2 Reaction with an oxidizing agent - Oxidising agents oxidise alcohols into carboxylic acids. Microbes found in the air would also have the same effect. For example: ethanol + oxidising agent → ethanoic acid + water. CH3CH2OH + 2[O] → CH3COOH + H2O Reaction with water (steam) - When the alcohols with the shortest hydrocarbon chains, e.g. methanol, ethanol or propanol, are added to water, they mix easily to produce a solution. However, the solubility decreases as the length of the alcohol molecule gets longer, so butanol is less soluble than propanol. It may not mix easily, and two distinct layers might be left in the container. For example: ethene + steam → ethanol. Reaction Methanol Ethanol Combustion (Does it burn easily with a clean flame?) Addition of water (Does it dissolve?) Reaction with sodium (What do you see?) Reaction with acidified potassium dichromate. (What do you see?) Lesson 4: Carboxylic acids and Esters Starter 1. State the functional group of carboxylic acids and esters. 2. Draw the displayed formula of ethanoic and propanoic acid 3. What gas would be formed when ethanoic acid reacts with magnesium. Foundation: Write the structural formula of ethanoic acid Stretch: Explain why carboxylic acids are weak acids Acid properties - The carboxylic acids have the typical properties of acids. For example, they: • dissolve in water to form acidic solutions with pH values less than 7 • react with metals to form a salt and hydrogen • react with bases to form a salt and water • react with carbonates to form a salt, water and carbon dioxide These properties are due to the –COOH functional group. : Weak and Strong acids - Carboxylic acids are weak acids: CH 3 COOH ⇌ CH 3 COO - + H + This means that their solutions do not contain many hydrogen ions compared with a solution of a strong acid with the same concentration. In a solution of a strong acid, the molecules are fully ionised, but in a weak acid, very few of the molecules are ionised. Esterification- Carboxylic acids can react with alcohols to make esters. Esters are organic compounds which all contain the functional group -COO-. Esters have fruity smells and can be used as solvents. For example: ethanol + ethanoic acid → ethyl ethanoate + water Here you can find more information on Carboxylic acids and esters: https://www.youtube.com/watch?v=ED9EU3FfzyU https://www.youtube.com/watch?v=cYgRd4rXY6I 3. What will be seen if propanoic acid is added to a solution of sodium carbonate? £ A. A colour change from orange to colourless £ B. Fizzing £ C. White precipitate 2. Which carboxylic acid is produced when butanol is oxidised? £ A. Butene £ B. Methanoic acid £ C. Butanoic acid 1. Which statement about carboxylic acids is true? £ A. They are organic compounds because they are hydrocarbons. £ B. They have a pH value which is more than 7. £ C. They react with alcohols to form esters If you answered A, you have correctly identified that carboxylic acids are organic compounds however they are not hydrocarbons. You should know that hydrocarbons only contain carbon and hydrogen atoms, whereas carboxylic acids have the functional group -COOH. To fix it write the definition of organic compounds. If you answered B, you said that carboxylic acids have a pH more than 7. You should know that carboxylic acids are weak acids and therefore have characteristics of other acids. The pH of all acids is below 7. To fix it revise the properties of acids here: https://www.bbc.co.uk/bbcbitesize/guides/zcjjfcw/revision/1 If you answered C, you said that esters are formed when a carboxylic acid reacts with an alcohol, this is correct, well done! To further improve read through 1-3 for naming esters here: https://www.bbc.co.uk/bbcbitesize/guides/zp8wwmn/revision/1 and look in more detail about how they are formed then complete the test at the end. Colour with universal indicator Reaction with Magnesium Reaction with potassium carbonate Conductivity 2. Use the reaction map below to draw the displayed reactions including conditions for the following reactions 1. Pentane to form pentene 2. Pentene to form pentanol 3. Pentanol to form pentatonic acid. 1. Complete the table below with observations about the reactions of carboxylic acids.