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AS LEVEL CHEMISTRY

2.2.1 ALCOHOLS
 (oxidation and esterification reactions)
2.2.3 MODERN ANALYTICAL TECHNIQUES

ASSESSED HOMEWORK

Answer all questions
Max 59 marks

| Name		…………………………………………………………….. |
| Mark		……../59	……....%	Grade ……… |

1.	In the laboratory, ethanol can be oxidised with acidified potassium dichromate(VI).
(a)	The ethanol can be oxidised to form either ethanal, CH_3CHO (Fig. 1), or
ethanoic acid, CH_3COOH (Fig. 2).

Fig. 1	Fig. 2
	The boiling points of ethanol, ethanal and ethanoic acid are given in the table below.
| CH_3CH_2OH | CH_3CHO | CH_3COOH
boiling point / °C | 8 | 21 | 118
	Use this table of boiling points to explain:
(i)	why the organic product is likely to be ethanal if the apparatus shown in Fig. 1 is used,
................................................................................................................
................................................................................................................
[2]
(ii)	why the organic product is likely to be ethanoic acid if the apparatus shown in Fig. 2 is used.
................................................................................................................
................................................................................................................
[2]

(b)	Write a balanced equation for the oxidation of ethanol to ethanoic acid. Use [O] to represent the oxidising agent.
.........................................................................................................................
[2]
[Total 6 marks]

2.	Compound E can be oxidised to form a carboxylic acid.
(i)	State a suitable oxidising mixture for this reaction.
.........................................................................................................................
[2]
(ii)	Write a balanced equation for this oxidation of compound E.
	Use [O] to represent the oxidising mixture.
	
[3]
(iii)	Explain how compound E and the carboxylic acid could be distinguished by
infra-red spectroscopy.
.........................................................................................................................
.........................................................................................................................
[1]
[Total 6 marks]

3.	(a)	In the presence of a suitable catalyst, cyclohexanol reacts with compound Y.
The organic product is shown in the equation below.

(i)	State a suitable catalyst. ..................................................................................
[1]
(ii)	Identify compound Y.

[1]
 (b)	Cyclohexanol can also be oxidised to form cyclohexanone.
(i)	State a suitable oxidising agent for this reaction.
................................................................................................................
[1]
(ii)	Write a balanced equation for the oxidation of cyclohexanol to cyclohexanone. Use [O] to represent the oxidising agent.

[1]
[Total 4 marks]

 4.	(a)	Butan-1-ol can be oxidised to form butanal.
(i)	State a suitable oxidising mixture for this reaction.
................................................................................................................
[2]
(ii)	State the colour change you would see during this oxidation.
from ................................................. to ..................................................
[1]
(b)	A sample of the butanal from (a) was analysed using infra-red spectroscopy. The infra-red spectrum contained an absorption in the region 1680–1750 cm^–1 but did not contain a broad absorption in the region 2500–3300 cm^–1.
	Refer to the Data Sheet for Chemistry provided.
(i)	What does the absorption in the region 1680–1750 cm^–1 indicate?
................................................................................................................
[1]
(ii)	What does the absence of a broad absorption in the region 2500–3300 cm^–1 indicate?
................................................................................................................
[1]
(iii)	The reaction in (a) was carried out using distillation and not reflux.
	Explain why.
................................................................................................................
................................................................................................................
[2]
[Total 7 marks]

5.	Citronellol, C_10H_20O, occurs naturally in both rose and geranium oils. The structural and skeletal formulae of citronellol are shown below.
  
(a)	Name the two functional groups present in citronellol.
………………...............……....…… and ..........................................................
[2]

(b)	The functional groups in citronellol can be identified either by chemical tests or by infrared spectroscopy.
(i)	State which of the two functional groups you named in (a) is:
1	identified when bromine is added to citronellol, .............................
2	more easily identified from the infra-red spectrum. ........................
[1]
(ii)	State what you would see when bromine is added to citronellol.
................................................................................................................
[1]
(iii)	Draw the skeletal formula of the organic product formed when bromine is added to citronellol.

[1]
(iv)	The infra-red spectrum of citronellol is shown below. Mark on this spectrum, with the letter X, the absorption that confirms the presence of the functional group that is most easily identified from this spectrum.

[1]

(c)	Reaction of a sample of citronellol, C_10H_20O, with hydrogen in the presence of a catalyst results in the formation of a saturated compound C.
(i)	Suggest a catalyst for this reaction.
................................................................................................................
[1]
(ii)	Determine the molecular formula of the saturated compound C.
................................................................................................................
[1]
(iii)	Construct a balanced equation for this reaction.
................................................................................................................
[1]
[Total 9 marks]

6.	Lavandulol, C_10H_18O, is a fragrant oil which is found in lavender. The structural and the skeletal formulae of lavandulol are shown below.
	
(a)	(i)	Identify two different functional groups in lavandulol.
.................................................. and ......................................................
[2]
(ii)	Why does lavandulol not have cis-trans isomerism?
................................................................................................................
................................................................................................................
[1]

(b)	Lavandulol also reacts with bromine to form a saturated organic product.
	State what you would see in this reaction and deduce the molecular formula of the organic product.
observation .....................................................................................................
[1]
molecular formula ...........................................................................................
[2]
(c)	Lavandulol could be converted into an ester X, which is also found in lavender oil.

ester X
State a reagent and a catalyst that could be used to form ester X from lavandulol.
reagent ............................................................................................................
[1]
catalyst ............................................................................................................
[1]

(d)	Lavandulol can be oxidised to produce either compound Y or compound Z.

 (i)	Write a balanced equation for the oxidation of lavandulol to produce compound Z. Use the molecular formulae given above and use [O] to represent the oxidising agent.
................................................................................................................
[2]
 (ii)	An infra-red spectrum of either compound Y or compound Z was obtained and was found to contain an absorption between 1680 - 1750 cm^–1. However, there was no broad absorption between 2500 - 3300 cm^–1.
	By referring to your Data Sheet, use this information to deduce whether the infra-red spectrum was of compound Y or of compound Z. Show your reasoning.
The infra-red spectrum was of compound ............ because ..................
................................................................................................................
................................................................................................................
................................................................................................................
[2]
[Total 12 marks]

7.	Bromobutane, CH_3CH_2CH_2CH_2Br, can be reacted with hot aqueous sodium hydroxide to prepare butan-1-ol.
CH_3CH_2CH_2CH_2Br + OH^– → CH_3CH_2CH_2CH_2OH + Br^–
	The butan-1-ol produced can be analysed by mass spectrometry.
(i)	Predict two fragment ions that you would expect to see in the mass spectrum of
butan-1-ol and state the m/z value of each ion.
.........................................................................................................................
.........................................................................................................................
[2]
(ii)	State a use of mass spectrometry outside of the laboratory.
.........................................................................................................................
[1]
[Total 3 marks]

8.	Compound X is an atmospheric pollutant emitted from fuel combustion of petrol and diesel vehicles. Compound X is a potent human carcinogen.
•	Analysis of compound X showed the following percentage composition by mass:
C, 88.89%; H, 11.1%.
•	Mass spectrometry showed a molecular ion peak at m/z = 54.
•	Compound X reacts with H2 in the presence of a nickel catalyst in a 1 : 2 molar ratio.
	Analyse and interpret this information to determine a possible structure for compound X.
	Show all your working.

[Total 5 marks]

Paddington Academy