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Weekly plan 2 Arenes 2 Student book links Specification links Link to AS specification Suggested time allowed (includes contact and non-contact time): Four to five hours 1.1.6–8 4.1.1.(e)–(h) 2.2.1 Alcohols 2.1.3 Alkenes Suggested teaching order Weekly learning outcomes Students should be able to: Explain the relative resistance to bromination of benzene compared with alkenes. Describe the reactions of phenol with aqueous alkalis and with sodium to form salts. Discuss the role of phenol as an early antiseptic. Describe the reactions of phenol with bromine to form 2,4,6-tribromophenol. Explain the relative ease of bromination of phenol compared with benzene. State the uses of phenols. Key words Cyclohexene Addition Electrophile Substitution Acid–base 1. A comparison of the reaction of bromine with benzene and an alkene such as cyclohexene 2. The structures of phenol and other phenols 3. The acidic properties of phenol, i.e. with sodium and sodium hydroxide 4. The explanation of the acidic properties of phenol – in terms of the delocalisation of oxygen’s lone pairs 5. The reaction of phenol with bromine 6. The explanation of phenol’s reactivity compared with benzene – in terms of the delocalisation of oxygen’s lone pairs 7. The uses of phenols How Science Works Phenol Phenoxide Delocalisation Activation HSW 1 & 4 The mechanism for the addition reaction of cyclohexene with bromine HSW 6a The benefits of using phenol as an antiseptic Learning styles (S = Starter activities, M = Main activities, P = Plenary activities) ICT activities Kinaesthetic Activity S3 Activity M3 Activities P1&3 Interpersonal Activity S2 Activities M1–2 Activity P2 Auditory Activity S2 Activities M1–2 Activity P2 Visual Activity S3 Activities M1–3 Activities P1–2 Research the discovery of phenol (carbolic acid) by Lister (see Activity S1 below). Activity M3 below could be done as a spreadsheet. The web links referred to here are some that the author has found personally helpful but are not intended to be a comprehensive list, many other good resources exist. © Pearson Education Ltd 2009 This document may have been altered from the original 1 Weekly plan 2 Suggested starter activities Equipment Teacher notes 1. Research Lister’s discovery of phenol (carbolic acid). PCs This should help students understand that phenol was an extremely useful antiseptic in its time; however, harmful side effects (e,g. blistering of skin) along with modern developments mean that it is no longer used today. Read about the phenols found in some herbs. 2. Students carry out a risk assessment regarding the use of phenol in the laboratory. Hazcards, etc. This is in preparation for Activity M1: ‘Could phenol be used as an antiseptic in hospitals (or the home) today?’ Students to work in groups. Suggested main activities Equipment Teacher notes 1. Give a teacher demonstration of the solubility of phenol in water and in sodium hydroxide solution. Phenol, sodium hydroxide solution Risk assessment 2. Give a teacher demonstration of the reaction between phenol and bromine. Phenol in solution, bromine water Risk assessment 3. Use your AS knowledge to suggest a mechanism for the reaction of bromine with cyclohexene. 3. Draw up a table to compare the reactions of benzene and cyclohexene with bromine. This could be done in groups. Suggested plenary activities Equipment 1. Use molecular models to show the structure and reactions of phenol. Molecular model kits 2. Play Alcohol or phenol? Cards with increasingly complicated structures Teacher notes Students to say: ‘Alcohol’; ‘Phenol’; ‘Both’; or ‘Neither’. How many can they correctly call in 60 seconds? 3. Write equations and name the products for the reactions between phenol and other Group 1 metals. © Pearson Education Ltd 2009 This document may have been altered from the original 2 Weekly plan 2 4. Predict products of reactions of phenols and arenas with a variety of electrophiles. Whiteboard Homework suggestions Write equations for the reactions of other phenols with sodium, sodium hydroxide and bromine. Find out which antiseptics are now used in hospitals, etc. Do any have structures related to phenol? Compare with an example the reactivity of: (i) bromine with benzene and an alkene; and (ii) bromine with benzene and phenol. Explain the differences. Cross-curriculum links Biology – antiseptics Stretch and Challenge Suggest an equation for the reaction between phenol and ethanoic acid. Name the product – is the reaction more or less likely to happen than with an alcohol? Suggest or research the conditions. Suggest five reactions that would be expected of the hypothetical molecule cyclohexa-1,3,5-triene. Give equations and name any products. Compare the acid strength of ethanol, phenol and ethanoic acid with reference to anion stability and their reactions with Na, NaOH and Na2CO3. Can you use the Kekulé model and the curly arrow model to explain why the bromines go into the 2,4 and 6 positions when it reacts with phenol? Look at reactions of phenol with dilute nitric acid in comparison with benzene. Potential misconceptions Students often confuse phenols with alcohols – in phenols the OH group is attached to one of the carbon atoms in the benzene ring. Students often confuse phenols with the phenyl group. Phenol is a compound but phenols are a class of compounds. Notes © Pearson Education Ltd 2009 This document may have been altered from the original 3