A2 LEVEL CHEMISTRY

CARBONYL COMPOUNDS
CARBOXYLIC ACIDS AND ESTERS

ASSESSED HOMEWORK

Answer all questions
Max 48 marks

	
Name		…………………………………………………………..

Mark		……../48	……....%	Grade ………

1.	
		
		geraniol
	Mild oxidation of geraniol gives an aldehyde Y.
(i)	Draw the skeletal formula of aldehyde Y below.

	
		aldehyde Y
[2]
 (ii)	Complete the equation for the oxidation of geraniol to aldehyde Y.
	C9H15CH2OH	+	[O]	®

[2]
[Total 4 marks]

 2.	Chloral hydrate is broken down in the body after several hours. One reaction is oxidation to trichloroethanoic acid.
	Complete the equation for this reaction below.
	Cl3CCH(OH)2	+	[O]	
[Total 1 mark]

 
3.	Cinnamaldehyde can be reduced using sodium borohydride, NaBH4.
(i)	State which functional group reacts with the sodium borohydride.
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[1]
(ii)	Complete and balance the equation for this reaction.
C6H5CH=CHCHO    +    [H]    ®
[1]
[Total 2 marks]

4.	The reducing agent, NaBH4, is used widely in organic chemistry. One example is for the reduction of diphenylethanedione, C14H10O2, shown below.
		
(i)	Draw a displayed formula to show the structure of the organic product that would be formed by reducing diphenylethanedione with excess NaBH4.

[1]
(ii)	Complete and balance the equation for this reaction, using [H] to represent the reducing agent.
C14H10O2	
[1]
[Total 2 marks]

5.	But-2-enal, CH3CH=CHCHO, is a pale yellow, flammable liquid with an irritating odour.
(a)	(i)	Describe a simple chemical test that would show that but-2-enal is an aldehyde.
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[2]
(ii)	Explain why this test gives a different result with aldehydes than it does with ketones.
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[1]
 (b)	But-2-enal also reacts with sodium borohydride, NaBH4.
(i)	Identify the organic compound formed in this reaction.

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[1]
(ii)	State the type of chemical reaction occurring.
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[1]
(c)	Precautions must be taken to prevent but-2-enal catching fire.
	Construct a balanced equation for the complete combustion of but-2-enal, C4H6O.

[1]
[Total 6 marks]

6.	Propanal, CH3CH2CHO, can be used in the synthesis of organic compounds.
	CH3CH2CHO reacts with NaBH4 in a nucleophilic addition reaction. The nucleophile can be represented as a hydride ion, H–. A mechanism for the reaction is shown below.

(i)	Add 'curly arrows' to the mechanism to show how the intermediate reacts with the water molecule in step 2.
[2]
(ii)	Draw the structure of the organic product in the box above.
[1]
(iii)	What is meant by the term nucleophile?
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[1]
(iv)	Describe, in words, exactly what is happening to the electron pairs and bonds in step 1 of the mechanism above.
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[3]
[Total 7 marks]

7.	(a)	The reaction of trichloroethanal with water is a nucleophilic addition reaction. It can be catalysed by small amounts of hydroxide ions, OH−.
	Complete the diagram below to suggest a mechanism for this reaction. Show all the relevant dipoles and curly arrows.

[5]
(b)	The recommended adult dose of chloral hydrate as a sedative is 250 mg, three times a day.
	Calculate the mass of trichloroethanal you would need to react with water to make one week’s supply of chloral hydrate for an adult, assuming a 60% yield.
	Mr: chloral hydrate, 165.5; trichloroethanal, 147.5

mass of trichloroethanal = …………………… g
[3]
[Total 8 marks]

8.	In this question, one mark is available for spelling, punctuation and grammar.
	Tollens’ reagent can be used to identify the aldehyde group in cinnamaldehyde, C6H5CH=CHCHO.
•	Describe how you would make Tollens’ reagent and carry out this test in the laboratory.
•	Explain what happens to both the Tollens’ reagent and the cinnamaldehyde in this reaction. Identify the organic product.
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[7]
Quality of Written Communication. [1]
[Total 8 marks]

9.	As a wine ages, some of the acids slowly react with ethanol in the wine to produce esters.
(i)	Draw a displayed formula to show the structure of the ester formed when lactic acid (2-hydroxypropanoic acid) reacts with ethanol.

[1]
(ii)	Suggest what effect this process might have on the flavour of the wine. Explain your reasoning.
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[1]
[Total 2 marks]

 10.	Reaction of geraniol with ethanoic acid can be used to make ester Z, which is used in chewing gum and desserts.
(i)	Suggest why esters are used in the manufacture of foods.
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[1]
(ii)	State the conditions needed to make ester Z from geraniol and ethanoic acid.
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[2]
(iii)	Complete the equation for the formation of ester Z.
	+   C9H15CH2OH   ®

[3]
[Total 6 marks]

11.	Glyceryl trihexanoate is a triglyceride that can be made from glycerol
(propane-1,2,3-triol) and hexanoic acid, C5H11COOH.
	Draw the structure of glyceryl trihexanoate. Show every bond in the functional groups.

[Total 2 marks]