OCR A Level Chemistry

Topic Questions

A LevelChemistryOCRTopic Questions6. Organic Chemistry & Analysis (A Level Only)6.7 Extending Carbon Chains

6.7 Extending Carbon Chains

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11 mark

Haloalkanes react with CN– to form nitriles, for example:

CH3CHBrCH3 + CN– → CH3CH(CH3)CN  +  Br–

What is the correct mechanism for this reaction?

  • Electrophillic substitution

  • Free radical substitution  

  • Nucleophilic addition  

  • Nucleophilic substitution

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21 mark

The hydrolysis of nitrile compounds forms carboxylic acids.

Which of the following statements are correct for the hydrolysis of nitrile compounds?

  1. Acidic hydrolysis forms a carboxylic acid and an ammonium salt.
  2. Alkaline hydrolysis using NaOH forms a sodium carboxylate salt and ammonia.
  3. Alkaline hydrolysis to form a carboxylic acid requires acid.

  • 1, 2 and 3

  • Only 1 and 2

  • Only 2 and 3

  • Only 1

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31 mark

What is the correct two-step synthesis to produce 2-hydroxypropanenitrile from ethanol?

  Step 1 Step 2
A NaCN / H2SO4  Distil with K2Cr2O7 / H2SO4 
B Distil with K2Cr2O7 / H2SO4 NaCN / H2SO4 
C NaCl / H2SO4  NaCN / Ethanol
D NaCN / Ethanol NaCN / H2SO4 

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41 mark

Which of the following reactions will increase the length of a carbon chain?

  1. Heating benzene with chloroethane and an aluminium(III) chloride catalyst.
  2. Heating butanenitrile with dilute hydrochloric acid.
  3. Heating propanenitrile with hydrogen and a nickel catalyst.

  • 1, 2 and 3

  • Only 1 and 2

  • Only 2 and 3

  • Only 1

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51 mark

Propanone can undergo addition when mixed with NaCN (aq) / H+ (aq), forming product X as shown.

ch3coch3-and-hcn-mechanism

What is the systematic name of product X?

  • 2-hydroxy-2-methylbutanenitrile

  • 2-methylbutanenitrile

  • 2-hydroxy-2-methylpropanenitrile

  • 2-methylpropanenitrile

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11 mark

Which compound would not form an optically active product with hydrogen cyanide?

  • CH3CH2CH(Br)CH3

  • CH2COCH2CH3

  • CH3CH2CH2CHO

  • CH3C(CH3)(Br)CH3

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21 mark

Lactic acid is formed in the human body during exercise. It can be made in the 2-step process below.

gqleIBJA_ocr-a2-6-7h-mcq-q2-reaction-sequence

Which statement(s) is/are correct?

  1. Lactic acid and molecule X are optically active.
  2. Stage 2 is acid hydrolysis and would produce lactic acid and ammonia.
  3. Lactic acid could also be made from molecule Y by the addition of acidified potassium dichromate.

  • 1, 2 and 3

  • Only 1 and 2

  • Only 2 and 3

  • Only 1

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31 mark

Organic molecules take part in many reactions.

Which row is correct?

 

Organic reactant

Organic product

Reagents / reaction conditions

Type of reaction

A

Ethanedial

Butane-1,4-dinitrile

HCN

Nucleophilic substitution

B

Butane-1,4-dinitrile

Ethane-1,2-diamine

LiAlH4 in dry ether

Reduction

C

Benzene

1-phenylpropan-1-one

Propanoyl chloride / AlCl3 / Heat

Electrophilic addition

D

Phenylethanone

1-phenylethan-1-ol

NaBH4 / H2O

Reduction

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41 mark

Propanoyl chloride can react with benzene. The product of this reaction, molecule X, can be used in other reactions.

Which statement(s) is/are correct?

  1. Molecule X can react with propanoyl chloride to produce an ester and white toxic fumes.
  2. Molecule X can be converted to 1-phenylpropan-1-ol by adding H2 in the presence of a nickel catalyst.
  3. For benzene to react with propanoyl chloride, the electrophile, AlCl4-, must be generated from AlCl3.

  • 1, 2 and 3

  • Only 1 and 2

  • Only 2 and 3

  • Only 1

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51 mark

Benzene reacts with ethanoyl chloride.

Which statement(s) is/are correct?

  1. The product has a Mr of 120 and forms an orange solution with the addition of acidified potassium dichromate.
  2. The reaction of methylbenzene and ethanoyl chloride would be faster because the methyl group increases the electron density of the ring.
  3. Methylbenzene will react with ethanoyl chloride and produce a mixture of chain isomers.

  • 1, 2 and 3

  • Only 1 and 2

  • Only 2 and 3

  • Only 1

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11 mark

Which equation does not represent the formation of an electrophile? 

  • CH3CH2Cl + AlCl3 → CH3CH3+ + AlCl4-

  • HNO3 + 2H2SO4 → NO2+ + H3O+ + 2HSO4-

  • CH3COCl + AlCl3 → CH3CO+ + AlCl4-

  • CH3Br + AlBr3 → CH3+ + AlBr4-

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21 mark

Which of the arrow(s) in the following mechanism is / are correct? 

ocr-a2-mcqs-m-6-7-q2

  • 1, 2 and 3

  • 1 and 2

  • 2 and 3

  • Only 1

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31 mark

Which of the following substances cannot be a product of nucleophilic substitution of 1-bromobutane?

  • Butan-1-ol

  • Pentanenitrile

  • But-1-ene

  • 1-aminobutane

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41 mark

Which set of reagents are required for the formation of 2-hydroxy-5-methylhexanenitrile? 

  • 1-chloropentan-2-ol and NH3 / ethanol 

  • 4-methylpentanal and KCN (aq) / H+ (aq)

  • 2-hydroxyhexamine and LiAlH4

  • 5-methylhexanal and KCN (aq) 

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51 mark

Which of the following reactions will form propanoic acid? 

  1. 2-methylpropanenitrile and HCl (aq) 
  2. 2-methylpropan-2-ol, K2Cr2O7 and concentrated sulfuric acid 
  3. Propyl propanate and NaOH (aq) 

  • 1, 2 and 3

  • 1 and 2

  • 2 and 3

  • 1 only 

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