SACE Stage 2. Chemistry. Written by. Mr Ian Kershaw. BSc Dip Ed

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1 2018 SAE Stage 2 Written by hemistry Mr Ian Kershaw BSc Dip Ed

2 The Author Ian Kershaw B.Sc., Dip.Ed. Ian has taught senior hemistry since e was a member of the SSABSA Subject Advisory ommittee for some years in the 1990s. Ian has extensive experience, over 13 years, as a marker of SAE Stage 2 examinations. e has taught in both metropolitan and country high schools and taught for 11 years in distance education. Ian is the author of the Stage 2 hemistry Fundamentals Revision Guide that has been developed over the past decade for the Adelaide Education Group and the SAE Stage 1 hemistry workbook plus individual Units to complement the workbook. Publishing Information This booklet is part 3 of a series of four Stage 2 booklets designed for the SAE Stage 2 hemistry course commencing in 2018 in South Australia. This booklet is designed to complement other resources students may have in this particular subject. This Unit is published by Total hemistry ABN ISBN This booklet and others in the Stage 2 series were first published in opyright Total hemistry Ian Kershaw totalchemistry@bigpond.com opyright information Unless permitted under the opyright Act of 1968 (& subsequent amendments), no part of this publication may be reproduced, stored in a retrieval system or transmitted in any form or by any means without prior permission of the copyright owner. The author has made every attempt to trace and acknowledge copyright. The author apologises for any accidental infringement and would be quite happy to reach an amicable arrangement in any such case.

3 SAE STAGE 2 EMISTRY Unit 1. Monitoring the Environment 1.1. Global Warming and limate hange 1.2. Photochemical Smog 1.3. Volumetric Analysis 1.4. hromatography 1.5. Atomic Spectroscopy Unit 2. Managing hemical Processes 2.1. Rates of Reactions 2.2. Equilibrium and Yield 2.3. ptimising Production Unit 3. rganic and Biological hemistry 3.1. Introduction 3.2. Alcohols 3.3. Aldehydes and Ketones 3.4. arbohydrates 3.5. arboxylic Acids 3.6. Amines 3.7. Esters 3.8. Amides 3.9. Triglycerides Proteins Unit 4. Managing Resources 4.1. Energy 4.2. Water 4.3. Soil 4.4. Materials Page3 IK2017 Total hemistry

4 Unit 3 Page 3.1. Introduction 6 Molecular & Structural Formulae 6 ondensation reactions 10 Physical properties Alcohols 13 Primary, secondary & tertiary 14 Naming & drawing 14 Use as fuels 15 xidation of alcohols Aldehydes & Ketones 18 Naming & drawing 18 Preparation of aldehydes & ketones 19 xidation of aldehydes arbohydrates 21 Definition of carbohydrates 21 ondensation reactions 21 di- and polysaccharides 21 Molecular formulae of saccharides 21 Identify and draw monomers 22 Aqueous solutions 22 ellulose & petrochemicals arboxylic Acids 26 Naming and drawing 26 Preparation by oxidation 27 Weak acids & properties 28 Titrations 28 Solubility of salts Amines 31 Naming & drawing 31 Types of amine 31 Basic nature 32 Solubility of protonated form 32 ormones & drugs 32 Page4 IK2017 Total hemistry

5 3.7. Esters 39 Naming and drawing 40 Preparation by condensation 41 Reflux 41 ydrolysis of esters 41 Polyesters Amides 44 Preparation by condensation 44 ydrolysis of amides 45 Polyamides Triglycerides 51 Structure of oils and fats 51 ydrolysis of triglycerides 52 Physical properties of fats & oils 52 Saturation 52 Iodine & bromine reactions 52 ydrogenation of oils (margarine) 53 Trans fats 53 Inter-esterification 54 Soap 55 Emulsions & emulsifiers 56 Amphiphilic particles Proteins 60 Amino acids 60 Self-ionisation 61 ondensation forming proteins 61 Amide & peptide links 61 Protein structure 62 Biological function of protein 64 Protein sequencing 67 DNA & proteins 68 Answers to Questions in Notes 70 Questions for topic 3 76 Solutions to Questions 102 Periodic Table 129 Page5 IK2017 Total hemistry

6 Unit 3 rganic & Biological hemistry 3.1. Introduction rganic compounds can be represented by molecular and structural formulae. Determine the molecular formula of an organic compound given its extended, condensed, or skeletal structural formula. rganic compounds are named systematically to provide unambiguous identification. ondensation reactions occur when two organic molecules combine to form a larger molecule, also releasing another small molecule, such as water. The physical properties of organic compounds are influenced by the molar masses of the molecules, and the number and polarity of functional groups. Predict, explain, and compare the melting points, boiling points, and solubilities in water and in non-polar solvents of organic compounds, given their structural formulae. Systematic nomenclature The molecular formula of a compound gives us information on the number of atoms of each element present in one molecule of that substance. For example: 2 6 ethane 3 8 propanol methyl propanoate Molecular formulae do not give information about how the atoms are bonded to each other. For many molecular formula, there may well be multiple structures or structural isomers. For example: This may be: This may be: a variety of isomers propan-1-ol propan-2-ol methyl propanoate ethyl ethanoate an ether methyl ethyl ether (not in the course) butanoic acid propyl methanoate methyl propanoic acid 2-propyl methanoate Page6 IK2017 Total hemistry

7 Molecular formula can be determined from different structural formulae. The previous structures are drawn using structural formulae. ther types of structural formula are shown below. extended structural formula condensed structural formula stick (skeletal) formula It is necessary for you to determine molecular formula given any of the above structures. Question: Determine molecular formula for each of the following structures: (5-methyl hexanoic acid) (2-methyl pentan-2-ol) (lactic acid) Molecular formula There are a large number of molecules that contain ring structures. There are basic two types of ring structures, those based on cycloalkanes and those based on the benzene ring. These are shown below: cycloalkanes benzene cyclohexane, 6 12 benzene, 6 6 cyclopentane, 5 10 naphthalene, 10 8 (mothballs) Page7 IK2017 Total hemistry

8 The structure of benzene was first proposed by Friedrich August Kekulé, a German organic chemist, in Benzene is able to undergo substitution reactions, whereby one or more of the hydrogen atoms are replaced by other atoms or group of atoms to form derivatives of benzene. Some examples are shown below. l 3 2 N N 2 chlorobenzene manufacture of other organic chemicals, dyes and insecticides benzoic acid food preservation, precursor for many other chemicals ibuprofen N 2 trinitro toluene (TNT) an explosive anti-inflammatory Functional groups are atoms or groups of atoms that determine the chemical properties of the molecule. There are many different functional groups. The functional group present determines the chemical family or homologous series that the compound belongs to. Examples of homologous series are shown below. Functional group -, hydroxyl group -, carboxyl group -N 2, amino omologous series alcohols carboxylic acids amines The names of organic molecules are based on a system. This is systematic nomenclature and makes the learning of names much simpler. Names of organic molecules have two parts. Firstly, the prefix reflects the number of carbons present in the longest hydrocarbon chain that contains any functional group. The second part of the name, the suffix, represents the homologous series to which the molecule belongs. prefix carbons meth- eth- prop- but- pent- hex- hept- oct- non- dec- Page8 IK2017 Total hemistry

9 homologous series Series suffix functional group alcohols -ol hydroxyl aldehydes -al aldehyde ketones -one ketone carboxylic acids -oic acid carboxyl amines -amine amino Aldehydes and ketones have the same functional group, the carbonyl group. The position of this group determines the homologous series. A carbonyl group at the end of a hydrocarbon chain reflects an aldehyde whereas a carbonyl group in the hydrocarbon chain reflects a ketone. Naming compounds is best done by: 1. Identifying the longest carbon chain (use a sausage shape) 2. Identifying the branches (circle anything other than ) 3. Number the carbons in the chain giving branches the lowest numbers (or lowest sum of numbers). Some tips: ,3,5-trimethyl heptane It is important to remember commas between numbers and hyphens between numbers and letters. In aldehydes and carboxylic acids, the atom in the functional group is always the number 1 carbon in the chain. The names of any hydrocarbon branches end in -yl. For multiple functional groups (the same group), use the following: Number of groups di- tri- tetra- penta- Page9 IK2017 Total hemistry

10 Question: Write systematic names for the following substances N N 2 N 2 There are a number of types of chemical reactions that can occur between molecules. Already mentioned are the substitution reactions of benzene to form its derivatives. ondensation reactions are another important class of reaction. In these reactions, molecules are joined together and a small molecule, frequently water, is eliminated. During this topic, you will notice that condensation reactions are used to form esters, amides, proteins, di- and poly-saccharides as well as being able to produce some polymers. In Stage 1 hemistry, the relationship between physical properties of a molecule and its mass or number of polar functional groups was introduced. This will be further investigated in this topic. Physical properties Two physical properties are important: melting point/boiling point and solubility in a variety of solvents. Both of these properties are dependent upon the strengths of secondary interactions. Page10 IK2017 Total hemistry

11 Boiling point/melting point The strength of the secondary interactions between molecules of the compound determines the amount of energy necessary to separate the molecules from each other when changing state (melting or boiling). The MP/BP of non-polar hydrocarbons depends on the mass of the molecule. Larger molecules have greater mass and hence stronger dispersion forces. Dispersion forces are the result of the creation of temporary dipoles when molecules move into close proximity in space. These temporary dipoles disappear when the molecules move away from each other. The electron clouds become distorted forming the temporary dipoles. Larger molecules contain more electrons hence stronger temporary dipoles can be formed resulting in the need for more energy to melt or boil the compound. The MP/BP of polar molecules are higher than those of similar sized non-polar molecules due to the stronger nature of the secondary interactions. Interactions here are between permanent dipoles and are called dipole-dipole interaction or hydrogen bonding. The strength of these depends on the strength of the molecular dipole and on the number of polar groups. Question: Name and draw the two structural isomers of Given that one isomer is a carboxylic acid and the other is an ester, explain which of the two isomers would have the higher MP/BP. Question: ircle which one out of the following pairs of molecules has the higher MP/BP. Explain your answers. or or Page11 IK2017 Total hemistry

12 Solubility The solubility of a molecule depends on the ability of the molecules to interact strongly with the solvent i.e. hydrogen bonding for polar solvents or dispersion forces for non-polar solvents). Solubility in water depends on the ability of the molecule to form hydrogen bonds with the polar water molecules. Solubility increases as the polarity of the functional group increases. Solubility also increases as the number of polar groups increases for molecules of similar size. Solubility decreases as the size of the molecule increases. This is because larger non-polar hydrocarbon component inhibits hydrogen bonding. In non-polar solvents such as hexane or benzene, the larger non-polar hydrocarbon components increase solubility due to stronger dispersion forces whereas the presence of polar functional groups lowers solubility. Question: ircle which of the following pairs is more soluble in water. Explain your answer. 3 or or Question: ircle which of the following pairs is more soluble in octane. Explain your answers. or S or S The selection of an appropriate solvent is vitally important to industry and around the home. Small organic compounds such as propanone (acetone) are used to dissolve grease/oil or the use of ethanol to dissolve iodine for use as an antiseptic. The volatility of some solvents such as small alcohols makes them useful to dissolve larger molecules and then they evaporate leaving solids behind as with some cosmetics. Page12 IK2017 Total hemistry