Year 12 Chemistry Easter Revision Session Learning Outcomes - CER: Be aware of the key skills required in the AS chemistry exams. Pick up some useful exam tips. Content (if time allows): Mechanisms Reactions of alcohols Analysis Enthalpy

Mechanisms - 1 You need to know 3 different mechanisms for this paper. The first one involves the reaction between alkenes and chemicals such as Br 2 Write a balanced equation (using displayed formulae) for the reaction between ethene and bromine, name the product formed and state what type of mechanism this is. Now draw out the mechanism.

Mechanisms - 1 Now redraw/adapt this mechanism for the reaction between ethene and hydrogen chloride. What would be different about this reaction if you used propene as your organic starting material instead of ethene? Draw out the two products formed using skeletal formulae and structural formulae, and name both of them. Alkenes can also be used to form alcohols and alkanes. In each case state the conditions required for the reaction. Write a balanced symbol equation for the hydrogenation of but-1,3-diene.

Mechanisms – 1 An example PPQ from CER June 10 – definitely worth attempting this question at some point during your revision (if we have time we’ll come back to it).

Mechanisms - 2 The second curly arrow mechanism you need to be aware of is used for the reaction between halogenoalkanes and ____? What is the name of this type of mechanism? Write a balanced equation for the reaction between 1-iodopropane and sodium hydroxide. Now draw a mechanism for this reaction and name the product formed. What simple chemical test could you use to check that this reaction had occurred?

Mechanisms - 2 Would iodoethane hydrolyse faster or slower than chloroethane? Explain your answer. Iodoethane would hydrolyse faster because the C-I bond is weaker than the C-Cl bond.

Mechanisms - 3 Radical substitution. Attempt Q4 from CER Jan 10 – you have 9 mins max. The second page (part b) is included for those that finish quickly. The markscheme is printed on the back so that you can see it in detail later – DO NOT LOOK AT IT YET!!!

Reactions of alcohols: There are two ways to make ethanol that you should know. For each method you need to be able to give the conditions and starting material(s), write balanced equations, and state advantages and disadvantages of each.

Reactions of alcohols: Divide your mini-whiteboard/page as shown below and see how many boxes you can complete. Name of method 1, balanced equation and conditions. Advantages of method 1 Disadvantages of method 1 Name of method 2, balanced equation and conditions. Advantages of method 2 Disadvantages of method 2

Reactions of alcohols: You’ve covered four different reactions of alcohols in this course. What are they? Oxidation Esterification Combustion Dehydration

Reactions of alcohols: You need to be able to write balanced equations for each of these reactions. We’ll come back to oxidation in a moment so instead write balanced equations for: the esterification reaction between propan-1-ol and ethanoic acid (and name the product formed), the dehydration of butan-1-ol (stating the conditions required), and also the combustion of pentan-2-ol.

Reactions of alcohols: the esterification reaction between propan-1-ol and ethanoic acid (and name the product formed) CH 3 COOH + CH 3 CH 2 CH 2 OH  CH 3 COOCH 2 CH 2 CH 3 + H 2 O propyl ethanoate the dehydration of butan-1-ol (stating the conditions required), CH 3 CH 2 CH 2 CH 2 OH  CH 3 CH 2 CH=CH 2 + H 2 O conditions required = conc. H 2 SO 4 and heat

Reactions of alcohols: and also the combustion of pentan-2-ol. CH 3 CH 2 CH 2 CH(OH)CH O 2  5 CO H 2 O Make sure you don’t forget about this oxygen when balancing the equation

Reactions of alcohols: Write down everything you can remember about the oxidation of alcohols on your mini-whiteboard – 1 min. Compare your efforts with the person sat next to you – 1 min. I’m now going to ask everyone to state one fact about the oxidation of alcohols.

Reactions of alcohols: Students often find it difficult to write out the balanced equations for these reactions. Have a go at writing balanced equations (using displayed formulae) for the oxidation of: Ethanol (distillation conditions) Propan-1-ol (reflux conditions) Propan-2-ol We’ll come back to this section in a moment when we look at PPQ that combines oxidation of alcohols and analysis.

Analysis: Infra-red spectroscopy and mass spectrometry. With regards to the analysis of organic molecules, what does each technique tell us about a molecule? IR – tells us the types of bonds that are present. MS – tells us the molar mass of the whole molecule and also of fragments of the molecule.

Analysis: Infra-red spectroscopy: This spectra either represents propan-1-ol, propanal or propanoic acid. State which compound it is giving reasons for your answer.

Analysis: Mass spectrometry: This spectra has been produced from pent-1-ene. Identify the ions responsible for the peaks labelled A, B and C. What name is given to peak A?

Analysis: Attempt the PPQ combining analysis and oxidation of alcohols taken from the CER Jan 10 paper – you have 7 mins max. Once again the markscheme is on the back of your handout to make it easier for you to read it later - DO NOT LOOK AT IT YET!!

You also have this on the back of your handout so don’t worry if you can’t read this slide clearly.

Enthalpy: There are three ways to determine the enthalpy change of a reaction: Measure it directly Calculate it from bond enthalpies Calculate it from enthalpy of combustion or formation data via a Hess cycle.

Enthalpy: Measuring enthalpy changes directly (CER Jan 10, Q3 a+b):

Enthalpy: Calculate enthalpy changes from bond enthalpy data (CER June 10, Q1 c):

Enthalpy: Calculate from enthalpy of formation data via a Hess cycle (CER June 10, Q1 d):

Enthalpy: Calculate from enthalpy of combustion data via a Hess cycle (CER Jan 10, Q3 c):