Alcohols revision
1. (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]
2. There are four structurally isomeric alcohols of molecular formula C4H10O. Graphical formulae of these isomers, labelled A, B, C and D, are shown below.
(a) Identify the type of alcohol represented by A and by B.
Type of alcohol represented by A ......
Type of alcohol represented by B ......
(2)
(b) Give the name of alcohol A.
...... (1)
(c) Select one of the alcohols A, B, C or D which will, on oxidation, produce an aldehyde.
(i) Give the structural formula of the aldehyde produced by this reaction.
Alcohol selected ......
Structural formula of aldehyde
(1)
(ii) State the reagents and conditions required for the aldehyde to be the main product of the oxidation reaction.
Reagents ......
Conditions ......
(3)
(d) All the alcohols A, B, C and D may be readily dehydrated.
(i) Explain what is meant by the term dehydration.
......
(1)
(ii) State the type of compound formed by dehydration of alcohols.
......
(1)
(iii) Suggest suitable reagent(s) and condition(s) for the dehydration of alcohols.
Reagent(s) ......
Condition(s) ......
(2)
(iv) Select one of the alcohols A, B, C or D which, on dehydration, would give a single product. Draw the structural formula of this product.
Alcohol selected ......
Structural formula of product
(1)
(v) Select one of the alcohols A, B, C or D which, on dehydration, would give two products which are structurally isomeric. Draw structural formulae for these two structural isomers and explain why the formation of two structural isomers is possible in this case.
Alcohol selected ......
Structural formula 1 Structural formula 2
Explanation ......
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......
(4)
(Total 16 marks)
1 (a) (i) H+ 1
Cr2O7 2- 1
(ii) Orange to green/black/blue 1
(b) (i) contains a C=O/aldehyde, ketone, carboxylic acid and ester/ 1
carbonyl/carbonyl in an aldehyde
(ii) does not contain a O-H/ (hydrogen bonded in a) carboxylic acid 1
(iii) distillation (no mark) because distillation allows loss of volatile 1
components /removes butanal from oxidising mixture
prevents formation of RCOOH/ partial oxidation would be achieved 1
or reverse argument for reflux not being used
in that reflux prevents loss of volatile components
hence complete oxidation would be achieved/RCOOH would be formed
[7]