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CHEMISTRY, M7 2020 VCE 7 MC

How many structural isomers have the molecular formula \(\ce{C3H6BrCl}\)?

  1. 4
  2. 5
  3. 6
  4. 7
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\(B\)

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Isomers are:

  • \(\ce{CH3CH2CHBrCl}\): 1-bromo-1-chloropropane
  • \(\ce{CH3CHClCH2Br}\): 1-bromo-2-chloropropane
  • \(\ce{CH2ClCH2CH2Br}\): 1-bromo-3-chloroopropane
  • \(\ce{CH3CHBrCH2Cl}\): 2-bromo-1-chloropropane
  • \(\ce{CH3CBrClCH3}\): 2-bromo-2-chloropropane

\(\Rightarrow B\)

♦ Mean mark 46%.

CHEMISTRY, M7 2023 HSC 8 MC

How many structural isomers have the molecular formula \( \ce{C3H6F2} \)?

  1. 2
  2. 3
  3. 4
  4. 5
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\(C\)

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  • Structural Isomers will have the same molecular formula but different structures.
  • The fluoride Ions can exists at different points on the carbon chain, changing the name and structure of the compound without altering its molecular formula.

\(\Rightarrow C\)

♦ Mean mark 53%.

CHEMISTRY, M7 2023 HSC 21

Some isomers with the formula \( \ce{C4H8O} \) are shown.
 

Name ONE pair of functional group isomers and ONE pair of chain isomers from the structures above.  (2 marks)

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Functional Group: Butan-2-one and butanal

  • Chain: Butanal and 2-methylpropanal
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Functional Group: Butan-2-one and butanal

  • Chain: Butanal and 2-methylpropanal

CHEMISTRY, M7 2019 HSC 21

  1. The structural formula for 2-methylpropan-2-ol is shown in the table.
  2. Draw one structural isomer of this alcohol and state its name.   (2 marks)

     

     

  3. The structural formulae for two compounds are shown below.
     

   
 

  1. Why are these two compounds classed as functional group isomers?   (2 marks)

  2. A chemical test is required to distinguish between the isomers in part (b).
  3. 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, M7 2020 HSC 7 MC

The structures of four isomers are shown.
 

Which statement is correct?

  1. Compounds 1 and 2 are chain isomers.
  2. Compounds 1 and 4 are chain isomers.
  3. Compounds 2 and 3 are functional group isomers.
  4. Compounds 2 and 4 are positional isomers.
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`C`

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Consider each option:

  • Chain isomers have a different structure of the `text{C}` chain. Compound 1, 2 and 4 have the same `text{C}` chain structure (eliminate A and B).
  • Positional isomers have the same `text{C}` chain but with different allocations of the same functional group (eliminate D).
  • Functional group isomers occur when atoms form different functional groups. Compound 2 has a double bond and an OH group, whereas Compound 3 only contains an ester group (correct).

`=> C`


♦ Mean mark 49%.

CHEMISTRY, M8 2022 HSC 27

A bottle labelled 'propanol' contains one of two isomers of propanol.

  1. Draw the TWO isomers of propanol.   (2 marks)
     

  1. Describe how \( \ce{^13C NMR}\) spectroscopy might be used to identify which isomer is in the bottle.   (2 marks)
  1. Each isomer produces a different product when oxidised.
  2. 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%.

CHEMISTRY, M7 2021 HSC 24

A straight-chained alkane has a molar mass of 72.146 g mol ¯1.

Provide the structural formulae for this alkane and all of its isomers.

Name these molecules using IUPAC conventions.   (4 marks)

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Straight chained alkane (Pentane):

2-methylbutane:

2,2-dimethylpropane:

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Straight chained alkane (Pentane):

2-methylbutane:

2,2-dimethylpropane: