Draw the full structural formula of an isomer of butan-2-ol. (1 mark) --- 5 WORK AREA LINES (style=lined) --- Possible images include: Possible images include:
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CHEMISTRY, M7 2019 HSC 21
- The structural formula for 2-methylpropan-2-ol is shown in the table.
- Draw one structural isomer of this alcohol and state its name. (2 marks)
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- The structural formulae for two compounds are shown below.
- Why are these two compounds classed as functional group isomers? (2 marks)
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- A chemical test is required to distinguish between the isomers in part (b).
- Identify a suitable test and explain the expected observations. (3 marks)
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a. Successful answers should have one of the following:
b. Functional Group isomers
- Both isomers have the same number and type of atoms, but they have different arrangements of those atoms and therefore have different functional groups.
- Isomer A has a ketone functional group, while isomer B has an aldehyde functional group.
c. Tollens’ Test:
- The Tollens’ test can be used to differentiate between Isomer A (a ketone) and Isomer B (an aldehyde).
- Isomer B will be readily oxidised to a carboxylic acid, whereas isomer A will not.
- As a result, Isomer B will reduce the silver-ions in Tollens’ reagent to form a silver mirror inside the test tube, while Isomer A will not react.
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a. Successful answers should have one of the following:
b. Functional Group isomers
- Both isomers have the same number and type of atoms, but they have different arrangements of those atoms and therefore have different functional groups.
- Isomer A has a ketone functional group, while isomer B has an aldehyde functional group.
c. Tollens’ Test:
- The Tollens’ test can be used to differentiate between Isomer A (a ketone) and Isomer B (an aldehyde).
- Isomer B will be readily oxidised to a carboxylic acid, whereas isomer A will not.
- As a result, Isomer B will reduce the silver-ions in Tollens’ reagent to form a silver mirror inside the test tube, while Isomer A will not react.
♦♦ Mean mark (c) 39%.
CHEMISTRY, M8 2022 HSC 27
A bottle labelled 'propanol' contains one of two isomers of propanol.
- Draw the TWO isomers of propanol. (2 marks)
- Describe how \( \ce{^13C NMR}\) spectroscopy might be used to identify which isomer is in the bottle. (2 marks)
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- Each isomer produces a different product when oxidised.
- Write equations to represent the oxidation reactions of the two isomers. Include reaction conditions. (3 marks)
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a. Isomer 1:
Isomer 2:
b. Identifying isomers with \( \ce{^13C NMR} \) spectroscopy:
- this can be used to identify the isomers in the bottle because they show a different number of signals which helps deduce the carbon environment.
- Propan-1-ol contains 3 \( \ce{C}\) environments so it would have 3 peaks on a \( \ce{^13C NMR}\) spectrum whereas propan-2-ol only contains 2 \( \ce{C}\) environments (due to symmetry), so it would only have 2 signals on a \( \ce{^13C NMR}\) spectrum.
c.
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a. Isomer 1:
Isomer 2:
b. Identifying isomers with \( \ce{^13C NMR} \) spectroscopy:
- this can be used to identify the isomers in the bottle because they show a different number of signals which helps deduce the carbon environment.
- Propan-1-ol contains 3 \( \ce{C}\) environments so it would have 3 peaks on a \( \ce{^13C NMR}\) spectrum whereas propan-2-ol only contains 2 \( \ce{C}\) environments (due to symmetry), so it would only have 2 signals on a \( \ce{^13C NMR}\) spectrum.
c.
♦ Mean mark (c) 52%.