Higher Chemistry Unit 2

1. Higher ChemistryUnit 2 Nature’s Chemistry

2. What you should know… • That molecular structure and physical properties of hydrocarbons are related. • The names, molecular and structural formula of straight and branched chain alkanes, alkenes and cycloalkanes. • How to identify isomers and draw their structural formulae. • What is meant by saturated and unsaturated carbon compounds and how they can be distinguished. • Addition reactions

3. The name of the functional group present in alcohols and the properties of alcohols • The names, molecular and structural formula of straight and branched chain alcohols • The name of the functional group present in carboxylic acids and the properties of carboxylic acids • The names, molecular and structural formula of straight and branched chain carboxylic acids

4. Organic Chemistry Originally, chemical compounds were divided into 2 classes: Inorganic or Organic Organic compounds were derived from living things. It was believed that they contained a ‘vital force’ and could not be made from inorganic compounds (non-living sources). Organic chemistry is the study of carbon compounds

5. HO • Organic molecules may be as simple as methane, CH4 or as complicated as cholesterol

6. L.I. To learn about esters Section 1 (a) S.C. By the end of this lesson you should be able to… • State the name ending present in all esters. • State the name of the functional group present in an ester. • Draw the functional group present in an ester. • State the two types of molecules which contribute to the name of an ester. • Draw the structural formula for an ester when given its name. • Draw the structural formula for an ester when given the name of the parent alcohol and carboxylic acid. • Describe the characteristic smell of an ester.

7. Fruit Flavours (a) Esters An ester can be identified by the name endings ‘-yl –oate’. Esters contain the carboxylate functional group (–COO-)… Carboxylate group

8. Naming Esters An ester can be named given the name of the parent alcohol and carboxylic acid or from shortened and full structural formulae. The parent alkanol gives the start of the name ending in -yl. The parent acid gives the second part of the name ending in -oate. So the ester formed by reacting ethanol with propanoic acid would be ethylpropanoate…

9. Workbook activities

11. 1. Methanol + Ethanoic acid Methyl ethanoate + 2. Butan-1-ol + Ethanoic acid Butyl ethanoate +

12. L.I. To learn about making esters (b) S.C. By the end of this lesson you should be able to… • State the name of the reaction in which esters are formed from carboxylic acids and alcohols. • State the definition of a condensation reaction. • State how an ester linkage can be formed by the condensation reaction between a hydroxyl group and a carboxyl group, using full structural formulae.

13. (b) Making Esters • In condensation reactions small molecules join together to form a bigger molecule by the elimination of water. • Esters are formed by the reaction of a carboxylic acid and an alcohol • Carboxylic acids contain the functional group carboxyl (-COOH) • Alcohols contain the functional group hydroxyl (-OH) Acids and carboxylic acids can react by condensationreactions to form esters.

14. Alcohol + Acid ⇌ Ester + Water The ester link is formed by the reaction of a hydroxyl group with a carboxyl group. The reaction is reversible - an equilibrium is set up. If the water is removed the equilibrium is shifted to the side of the products . Concentrated sulphuric acid has a high affinity for water and is used to remove it and shift the equilibrium to the right. Carry out the experiment to make an ester in the lab (Workcard 1) …

15. Workbook activity… • What is the purpose of the wet paper towel? • Why is the reaction mixture heated in a water bath? • Why is the reaction mixture poured onto sodium hydrogen carbonate solution? • Observation: The paper towel acts as a condenser to prevent volatile gases escaping (it cools them down). To increase the temperature of the reaction and make the reaction happen faster. A Bunsen cannot be used as the reactants are flammable. It was added to the products to neutralise the sulphuric acid and any excess carboxylic acid. The product had a strong smell and formed a layer over the water since esters are immicible in water.

17. L.I. To learn about the uses of esters (c) S.C. By the end of this lesson you should be able to… • Describe the three main uses of esters.

18. (c) Uses of esters Esters are oily liquids with generally very pleasant fruity smells and have a range of uses. Many esters are used as flavourings, in perfumes and as solvents. Workbook activity

21. Uses of esters as solvents Some of the smaller esters are quite volatile and are used as solvents in adhesives, inks and paints – pentyl ethanoate is used in nail varnish for example. Ethyl ethanoate is one of a number of solvents used to extract caffeine from coffee and tea. De-caffeinated products produced with ethyl ethanoate are often described on the packaging as "naturally decaffeinated" because ethyl ethanoate is a chemical found naturally in many fruits. Caffeine (C8H10N4O2) is an example of a class of compounds called alkaloids which are produced by plants. The name alkaloid means “alkali-like”, where alkali is a base and hence refers to these basic properties.

22. Caffeine is more soluble in the organic solvent ethyl ethanoate than in water, so we will extract caffeine into the organic solvent to separate it from glucose, tannins, and other water soluble compounds using a separating funnel. The ethyl ethanoate portions can be combined and the ethyl ethanoate removed by evaporation to leave the caffeine

23. VOC stands for ‘Volatile Organic Compounds’. Workbook activity Legislation aims to prevent or reduce the direct and indirect effects of emissions of volatile organic compounds (VOCs) on the environment and human health, by setting emission limits for such compounds and laying down operating conditions for installations using organic solvents. Why? The emissions of volatile organic compounds * (VOCs) in the atmosphere contribute to the formation of the tropospheric ozone (ozone in the lower atmosphere). Large quantities of this ozone may be harmful to people, vegetation, forests and crops. Sensitive people may suffer irritation of the throat and eyes, as well as respiratory difficulties. Tropospheric ozone is also a greenhouse gas.

24. L.I. To learn about the hydrolysis of esters (d) S.C. By the end of this lesson you should be able to… • Describe how an ester can be hydrolysed using full structural formulae. • State the definition of a hydrolysis reaction. • State the name of the products formed by the hydrolysis of an ester.

25. In hydrolysis reactions large molecules are broken down into smaller molecules by water. Esters can be hydrolysed to produce the parent ................... .......... and the parent .................... . ESTER + WATER ⇌ ACID + ALCOHOL An alkali is often used to catalyse the reaction and the mixture heated under reflux. If sodium hydroxide is used a sodium salt of the acid is formed. If this is reacted with a strong acid (eg. Hydrochloric acid) the acid can be displaced from the salt HCOO- Na+ + HCl HCOOH + NaCl Sodium + hydrochloric methanoic + sodium methanoate acid acid chloride

26. Carry out the experiment to hydrolyse ethyl benzoate (Workcard 2) Use the equation below to calculate the theoretical mass of benzoic acid expected when 0.033 moles (5g) of ethyl benzoate is hydrolysed. C6H5COOC2H5 + H2O ⇌ C6H5COOH + C2H5OH

27. Calculate the % Yield using the following equation… % yield = actual mass x 100 theoretical mass

28. L.I. To learn about edible fats and oils Section 2 (a) S.C. By the end of this lesson you should be able to… • State why fats and oils are an essential part of a healthy diet. • Describe the formation and structure of fats and oils. • Explain using full structural formulae how fats and oils are formed. • State the main difference between the structure of saturated and unsaturated fatty acids.

29. Natural oils have vegetable and marine (fish) origins Natural fats have ………………………, …………………… or ………………………… origins Workbook Activity

30. Fats and oils are an essential part of the diet. They provide the body with energy. Fats and oils are a more concentrated source of energy than .................................

31. Carry out the experiment to test the unsaturation of fats and oils (Workcard 3) • What does unsaturated mean? • Which sample is the most saturated and which is the most unsaturated? • This comparison is only approximate. How could the method be improved? Solids fats tend to be saturated Liquid oils tend to be unsaturated

32. Fats and oils are naturally occurring esters of the alcohol glycerol and long chain carboxylic acids. Long chain carboxylic acids are often called ‘fatty acids’ R1, R2, R3 are long carbon chains which can be the same or different glycerol

33. Propan-1,2,3-triol Glycerol is a trihydric alcohol – it has three alcohol groups the correct name is .................................... Fats and Oils are formed by combination of ..... moles of fatty acids to .......... mole of glycerol - a triglyceride. There are .................. ester linkages in the one molecule. 1 3 3

34. L.I. To learn about the melting points of fats and oils Section 2 (b) S.C. By the end of this lesson you should be able to… • State and explain the difference in melting points of fats and oils, in terms of structure, close packing and strength of intermolecular bonds.

35. solid liquid • Fats are .................... at room temperature while oils are ...................... . • The properties of a fat or an oil depend on the fatty acids which are combined with the • glycerol in each triglyceride. • Most fats and oils in nature are mixtures of triglycerides in which the fatty acid • molecules may or may not be identical. • Fatty acids are saturated or unsaturated straight chain carboxylic acids. They contain an • even number of carbon atoms and range in size from C4 to C24 carbon atoms, but mainly C16 • and C18.

36. Workbook activity Complete the table below…

38. Fat and oil molecules are roughly ‘tunning fork’ in shape with three limbs being hydrocarbon chains. If the chains are saturated, the molecules pack neatly together even at quite high temperature Fat – higher melting point Oil – lower melting point • If the chains contain one or more double bonds the zig-zag chains become more distorted and the • close packing of the molecules is less easy. • How will the close packing of fat molecules affect the strength of the Van der Waal’s (intermolecular) bonds? • What effect will this have on the melting point? The more closely the molecules can pack together, the stronger the van der Waals forces. The stronger the van der Waals forces, the more energy is needed to break them and the melting point will be higher.

39. L.I. To learn about the function of proteins Section 3 (a) S.C. By the end of this lesson you should be able to… • Describe the role of proteins in the body.

40. growth repair We need protein for ................. and ............... . Foods such as meat and fish are rich in protein. Proteins are the major structural materials of animal tissues. Proteins are also involved in the maintenance and regulation of life processes. Proteins can be classified as fibrous or globular.

41. Fibrous proteins are long and thin and are the major structural materials of animal tissue. Workbook activity… Give examples of fibrous proteins… Keratin found in hair and nails Collagen and elastin found in connective tissue in the body. Globular proteins have the spiral chains folded into compact units.Globular proteins are involved in the maintenance and regulation of life processes and include enzymes and many hormones. Workbook activity… Give examples of globular proteins Albumin found in blood plasma Haemoglobin found in blood which carries oxygen around the body

42. Proteins are chemicals containing the element nitrogen. Carry out the experiment to heat proteins with soda lime (Workcard 4) When a protein is heated strongly in the presence of soda lime (a mixture of calcium and sodium hydroxide) an unpleasant smelling alkaline gas is produced which turns moist pH paper blue. These gases are amines or ammonia - chemicals which contain nitrogen.

43. Enzymes are proteins, which act as biological catalysts. They are specific to particular chemical reactions e.g. the enzyme pepsin only catalyses the hydrolysis of proteins and not any other chemical reaction Certain sequences of amino acids form a region known as the active site. The shape of the active siteallows specific reactants known as substrates to attach, like a lock and key. Incorrect substrates are unable to fit the shape of the active site and are not changed. Enzyme function is therefore related to the molecular shapes of proteins

44. Carry out the experiment to find out if pH affects enzyme activity (Workcard 5)

45. 1. 2. 3. If the temperature rises above a critical level the shape of the enzyme molecule becomes irreversibly altered although the peptide links remain intact. This means that the enzyme is unable to function. The enzyme is said to be .............................. . All proteins, not just enzymes, can be denatured by temperature and pH. denatured

46. L.I. To learn about amino acids Section 3 (b) S.C. By the end of this lesson you should be able to… • State the name of the building blocks from which protein molecules are formed. • Describe the structure of amino acid molecules and how they differ to produce 20 common naturally occurring amino acids. • Explain why some amino acids are known as essential amino acids.

47. Amino acids contain an amino group (-NH2) at one end and an acid group (-COOH) at the other end of the molecule. The majority of amino acids found in proteins are of the type R represents a carbon side chain which may even contain the elements nitrogen and sulphur.

48. There are 20 or so amino acids which go into making up protein. The body cannot make all the amino acids required for body proteins and is dependent on dietary protein for the supply of certain ............................. amino acids. essential

49. L.I. To learn about amide links Section 3 (c) S.C. By the end of this lesson you should be able to… • State the type of reaction in which many amino acid molecules can link together to form a protein molecule. • Explain using full structural formulae how an amide (peptide) linkage can be formed by a condensation reaction between amino acids. • State how the diverse range of proteins needed to fill the different roles in the body is produced from just 20 amino acids.

50. Proteins specific to body’s needs are built up within the body. Proteins are ........................... polymers formed by combining amino acids to form long chain molecules of maybe several thousand amino acid units long. condensation Workbook activity… The following amino acids react to form a tripeptide. Draw the structure of the product molecule below.