1. How well are you doing?

2. Where did the class fall down on the last past paper? Esters, Equilibria and Testing for ions

3. Success Criteria: Be able to Describe the esterification of alcohols with carboxylic acids. Produce a sample of a pure Phenyl Benzoate ester using a range of advanced chemical techniques. Explain the process of re-crystallisation. Extension: Describe elimination of H 2 O from alcohols to form alkenes. Esterification and Dehydration

4. Numeracy Starter What is the resolution of measuring cylinder A?

5. Numeracy Starter What is the resolution of measuring cylinder B? S&C why is there a temperature on the cylinder?

6. Which measuring cyclinder would you use to measure 2cm 3 of liquid? Why? TASK : Calculate the % error in each case.

7. Numeracy Starter Answer The 500cm 3 cylinder had a resolution of +/-2.5cm 3. Therefore to measure 2cm 3 the error would be (2.5/2.0)x100 = 125% The 5cm 3 measuring cylinder had a resolution of +/- 0.1cm 3 Therefore to measure 2cm 3 the error would be (0.1/2.0) x 100 = 5%

8. AFL On your post-it note write down A/ How you would make the ester phenyl benzoate. B/ How you would separate and purify the product. If you don’t know say so. That is fine!

9. Name the compound…

10. Name the compound

11. The esterification reaction between propanoic acid and methanol

12. Diagram to show the bonds broken during esterification

13. Naming esters

14. Simple laboratory preparation of an ester Making Pentyl Ethanoate 2cm 3 of Pentan-1-ol, 2cm 3 of glacial ethanoic acid. Add a few drops of concentrated sulfuric acid. HAZARDOUS

15. Separating the ester Boiling points 118 o C 65 o C 57 o C 100 o C Miscible with water? Yes Yes No Yes Suggest two ways that you could separate the ester from the reaction mixture.

16. Pour your reaction mixture into water Ester floats on the water as it is less dense and immiscible Sulfuric acid, ethanoic acid and pentan-1-ol are soluble in water

17. Mini Plenary How do you make an ester? What is the catalyst used? How do you separate the ester from the reaction mixture? Name the ester made from ethanol and propanoic acid.

18. Homework Describe and explain the formation of phenyl benzoate from benzyl chloride and phenol including a detailed explanation of recrystallization.

19. Spaced Learning Activity You have four minutes to use the modelling putty to make a model of a bunch of grapes.

20. Esters in grapes Pembrokeshire has a vineyard which produces wines with fine flavours produced by esters. Research has identified 11 different esters in grape juice, but wine can have up to 83; this affects the wine’s flavour and complexity in proportion to their presence. Esters are formed when an acid reacts with alcohol, eliminating a water molecule in the process. Ethyl esters have a strong influence on a wine’s aroma here are three examples; ethyl hexanoate, fruity, strawberry, green apple and anise ethyl octanoate, with sweet, fruity, ripe fruit, burned and beer characteristics ethyl decanoate, which imparts an oily, fruity and floral character.

21. Sweet-smelling esters Explain how you would make Octyl Ethanoate

22. The esterification reaction is both slow and reversible. The equation for the reaction between ethanoic acid and ethanol is: 118 0 C 78 0 C 54 0 C 100 0 C Q1 What does reversible mean?  H of the forward reaction is -20kJ.mol-1 Q2 How can we favour the forward reaction and make more Ester? Q3 Why do we warm the reaction mixture?

23. Starter Synthesis of PhenylBenzoate Draw the two compounds that you would need to react together to form phenylbenzoate.

24. Answer Benzoic Acid Phenol

25. How to get around reversible reactions.. By using a derivative of carboxylic acids called an acid chloride in the presence of sodium ions we minimise the back reaction from taking place to gain a better yield of the ester. We also do not need the acid catalyst if we do this.

26. Risk Assessment Hazard- Phenol is corrosive and causes burns to the skin. Risk – Phenol getting on skin during weighing/ handling. Wear gloves, lab coats and safety glasses. Inform teacher immediately if phenol gets on your skin.

27. Method 1/ Weigh 1.0g of Phenol into a small conical flask. HAZARD 2/Add 18cm 3 of 1M NaOH(aq) and bung the flask. 3/ HAZARD In a fume cupboard add 2cm 3 of Benzoyl chloride in small quantities at a time. 4/ Fit a bung and shake vigorously with occasional cooling under the tap or in ice water. Releasing the gas formed into the fume cupboard every few minutes. 5/ After 15 minutes the solid benzoate separates out: the solution should be alkaline at the end of the reaction; if not alkaline, or if oily, add a solid pellet of sodium hydroxide and shake again. 6/ Buchner filtrate the phenyl benzoate and wash thoroughly with ice cold water. and re-crystallise from ethanol (NO FLAMES!).

28. Buchner filtration

29. Impurity 1 Impurity 2 Product Product low solubility at low temp. Product very soluble at high temp Impurity can be filtered out while solution is hot Remains in filtrate.

30. Numeracy starter If a saturated solution of phenylbenzoate in ethanol was cooled from 55 o C to 20 o C what mass of the ester would be precipitated?

31. Recrystalisation to purify your product. What is your product contaminated with? How can we remove this?

32. Recrystallisation → Solvent added (clear) to compound and soluble impurities (orange) → Solvent heated to give saturated compound solution (orange) with impurities in solution → solution (orange) allowed to cool over time to give crystals of product (orange) and a solution of impurities (pale-orange).

33. Method 1/ Warm 2/3 of a boiling tube of ethanol to 70 o C. 2/ Place the impure Phenyl Benzoate crystals into a second boiling tube and place the tube in the water bath. 3/ Add the minimum quantity of hot ethanol to the crystals to get them to dissolve. Work with a glass rod. 4/ When all the crystals have dissolved take the tube out of the water bath and place in a test tube rack. 5/ Observe with care DO NOT DISTURB. 6/ Note your observations. 7/ Buchner filtrate your crystals when cool.

34. Phenyl Benzoate crystals

35. Dehydration of cyclohexanol to form cyclohexene Dehydration of alcohols to form Alkenes.

36. Dehydration of ethanol to form ethene © Pearson Education Ltd 2008 This document may have been altered from the original

37. Extension questions