1(a) This question is about the analysis of organic compounds.
A student investigates the alkaline hydrolysis of 1-bromopropane as outlined below.
Step 1 The student adds 1-bromopropane to an excess of aqueous potassium hydroxide, KOH(aq), in a pear-
shaped flask.
Step 2 A TLC chromatogram is run using propan-1-ol and the reaction mixture.
Step 3 The reaction mixture is refluxed.
A TLC chromatogram of the reaction mixture is run every 10 minutes.
The TLC chromatograms are shown below
i. Determine the Rf value of propan–1–ol.
Show your working.
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, Rf = ................... [1]
ii. Write an equation for the alkaline hydrolysis of 1–bromopropane.
Show structures of organic compounds.
[1]
iii. A student investigates the alkaline hydrolysis of 1–chloropropane using the same method as for
1–bromopropane.
Predict, with reasons, how the appearance of the reaction mixture in the chromatogram produced after 20
minutes would be different when 1–chloropropane is used instead of 1–bromopropane.
Suggest why propan–1–ol is run alongside the reaction mixture.
[3]
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, (b) Compounds F, G, H and I are structural isomers.
A student carries out test-tube tests on the compounds.
The student records the observations after carrying out each test.
These are shown in Table 5.1.
In Table 5.1, 2,4-dintrophenylhydrazine has been abbreviated to 2,4–DNP.
Table 5.1
Compound Test
2,4-DNP Acidified Bromine water Tollens' reagent
dichromate(VI)
reflux
F Orange solution Green solution Colourless solution Colourless solution
G Orange solution Green solution Orange solution Colourless solution
H Orange precipitate Orange solution Orange solution Colourless solution
I Orange precipitate Green solution Orange solution Silver mirror
i. Write the formula of the species causing the colours after refluxing with acidified dichromate(VI).
Green solution
Orange solution [2]
ii. The student is provided with further information about compounds F–I.
• They all have the molecular formula C5H10O.
• One of the compounds is alicyclic.
• The other compounds are unbranched.
Use this further information and the student’s observations in Table 5.1 to answer the following.
• How do the observations provide evidence for the possible functional groups in compounds F–I?
• Suggest a possible structure for each of the compounds F–I.
Show your reasoning.
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[6]
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A student investigates the alkaline hydrolysis of 1-bromopropane as outlined below.
Step 1 The student adds 1-bromopropane to an excess of aqueous potassium hydroxide, KOH(aq), in a pear-
shaped flask.
Step 2 A TLC chromatogram is run using propan-1-ol and the reaction mixture.
Step 3 The reaction mixture is refluxed.
A TLC chromatogram of the reaction mixture is run every 10 minutes.
The TLC chromatograms are shown below
i. Determine the Rf value of propan–1–ol.
Show your working.
© OCR 2025. You may photocopy this page. 1 of 111 Created in ExamBuilder
, Rf = ................... [1]
ii. Write an equation for the alkaline hydrolysis of 1–bromopropane.
Show structures of organic compounds.
[1]
iii. A student investigates the alkaline hydrolysis of 1–chloropropane using the same method as for
1–bromopropane.
Predict, with reasons, how the appearance of the reaction mixture in the chromatogram produced after 20
minutes would be different when 1–chloropropane is used instead of 1–bromopropane.
Suggest why propan–1–ol is run alongside the reaction mixture.
[3]
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, (b) Compounds F, G, H and I are structural isomers.
A student carries out test-tube tests on the compounds.
The student records the observations after carrying out each test.
These are shown in Table 5.1.
In Table 5.1, 2,4-dintrophenylhydrazine has been abbreviated to 2,4–DNP.
Table 5.1
Compound Test
2,4-DNP Acidified Bromine water Tollens' reagent
dichromate(VI)
reflux
F Orange solution Green solution Colourless solution Colourless solution
G Orange solution Green solution Orange solution Colourless solution
H Orange precipitate Orange solution Orange solution Colourless solution
I Orange precipitate Green solution Orange solution Silver mirror
i. Write the formula of the species causing the colours after refluxing with acidified dichromate(VI).
Green solution
Orange solution [2]
ii. The student is provided with further information about compounds F–I.
• They all have the molecular formula C5H10O.
• One of the compounds is alicyclic.
• The other compounds are unbranched.
Use this further information and the student’s observations in Table 5.1 to answer the following.
• How do the observations provide evidence for the possible functional groups in compounds F–I?
• Suggest a possible structure for each of the compounds F–I.
Show your reasoning.
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[6]
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