OCR AS Chemistry

Topic Questions

ASChemistryOCRTopic Questions4. Core Organic Chemistry4.6 Organic Synthesis

4.6 Organic Synthesis

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11 mark

The preparation of organic liquids, such as some esters, can involve heating under reflux.

Which statement about heating under reflus is correct?

  • Organic liquids can be heated without evaporation taking place.

  • Organic liquids can be maintained at their boiling point for extended periods.

  • Heating is carried out using a water bath.

  • The apparatus is closed to prevent the loss of any materials.

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21 mark

Which of the following can be done with the aid of a separating funnel?

  Neutralise acidic impurities Dry organic liquids Separate miscible liquids
A ✓ ✓ ✓
B ✓ ✓ X
C X ✓ ✓
D ✓ X X

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31 mark

What reaction could the following equipment be used for?

distillation

  • Preparing a carboxylic acid.

  • Cracking an alkane.

  • Oxidising an alcohol.

  • Halogenation of an alkene.

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41 mark

What is the purpose of the part labelled X in the diagram?

distillation---thermometer-labelled-x

  • To check the boiling point of the reaction mixture.

  • To separate the distillate from the reaction mixture.

  • To check the purity of the distillate.

  • To prevent gases from escaping.

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51 mark

Which type of reaction has the greatest atom economy?

  • Substitution

  • Hydrolysis

  • Elimination

  • Addition

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61 mark

Which reaction occurs when ethane and chlorine are mixed in the presence of sunlight?

  • A free-radical substitution with hydrogen produced

  • A free-radical substitution with hydrogen chloride produced

  • A free-radical substitution with no gas produced

  • A nucleophilic substitution with hydrogen chloride produced

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71 mark

This molecule is responsible for the flavour of spearmint chewing gum.

functional-group-mechanisms

What is a true statement about the functional groups 1 or 2?

  • 1 will undergo electrophilic addition

  • 1 will undergo electrophilic substitution

  • 2 will undergo nucleophilic substitution

  • 2 will undergo electrophilic substitution

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81 mark

The addition of hydrogen bromide, HBr, to pent-2-ene, CH3CH2CH2CH=CH2 , produces

  • 1-bromopentane

  • 2-bromopentane

  • 1,2-dibromopentane

  • A mixture of 1-bromopentane and 2-bromopentane

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91 mark

A reaction scheme is shown below. 

major-and-minor-product

Which of the following statements is correct?

  • Product 1 is the major product

  • Product 2 is the major product

  •  A 50:50 mixture of the two products is formed

  • The bromine acts as an electrophile

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101 mark

A reaction sequence is shown below. 

reaction-sequence

Identify reaction 1 and 2. 

  Reaction 1  Reaction 2 
A Nucleophilic Addition Oxidation
B Nucleophilic Substitution Oxidation
C Nucleophilic Addition Reduction
D Nucleophilic Substitution Reduction

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11 mark

Which statements about the preparation and purification of an organic liquid is/are correct?

  1. Reflux is used for the condensation reaction between an alcohol and a carboxylic acid.
  2. In a separating funnel, adding water will identify the organic layer as it will decrease in volume.
  3. A bunsen burner must be used in reflux because it requires more vigorous heating.

  • 1, 2 and 3

  • Only 1 and 2

  • Only 2 and 3

  • Only 1

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21 mark

Alcohol is produced by the following 2-step process.

Methylbutane rightwards arrow with bold Step bold space bold 1 on top Intermediate X begin mathsize 16px style rightwards arrow with bold Step bold space bold 2 on top end style Alcohol

Upon addition of acidified potassium dichromate(VI), the alcohol produces an orange solution.

Which row correctly identifies intermediate X and the reagents/conditions of step 2 in this process?

 

 

Intermediate X

Reagents/conditions of step 2

A

2-chloro-2-methylbutane

NaOH (aq) / reflux

B

2-methylbut-1-ene

NaOH (aq) / reflux

C

3-methylbut-1-ene

Steam and H2SO4 / heat

D

2-chloro-3-methylbutane

Steam and H2SO4 / heat

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31 mark

1-chlorobutane can be made by the following multistep process.

Which of the following reagents is not suitable for the indicated step?

vuqMYbi5_ocr-as-4-6h-mcq-q3-reaction-sequence

  • Step 1 hot K2Cr2O7/H2SO4

  • Step 2 hot Al2O3

  • Step 3 H2 and Ni catalyst

  • Step 4 Cl2 and UV light

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41 mark

Which of the following types of reaction is not involved in the sequence below?

rJyXzIce_ocr-as-4-6h-mcq-q4-reaction-sequence

  • Electrophilic addition

  • Elimination

  • Nucleophilic substitution

  • Free radical substitution 

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51 mark

Which of the following statements is/are correct?

  1. The sequence alkene → alcohol → aldehyde has a higher yield than alkene → haloalkane → alcohol → aldehyde.
  2. A nucleophile will attack a haloalkane because the halogen atom is more electronegative than the hydrogen atoms.
  3. Polyethene is not degraded by NaOH because of the electron-rich carbon-carbon double bonds.

  • 1, 2 and 3

  • Only 1 and 2

  • Only 2 and 3

  • Only 1

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11 mark

Crotonaldehyde, CH3CH=CHCHO, occurs in soybean oils and can be formed from its alcohol.

What are the reagents and conditions required to form crotonaldehdye from its alcohol?

  Reflux Distillation K2Cr2O7  K2Cr2O7 / H+ 
A ✓ X ✓ X
B ✓ X X ✓
C X ✓ X ✓
D X ✓ ✓ X

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21 mark

Which of the following reagents can be used to dry a damp sample of ethyl ethanoate?

  • Saturated sodium carbonate solution.

  • Anhydrous sodium sulfate.

  • Concentrated sulfuric acid.

  • Aluminium oxide.

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31 mark

Which molecule contains an aldehyde functional group?

  • CH3CH2CH2COOCH3 

  • CH3CH2CH2COCH3 

  • CH3CH2OCH2CH3 

  • CH3CH2CH2CH2CHO

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41 mark

Which haloalkane contains a tertiary carbon atom?

  • CH3CH2CH2Cl

  • CH3CH2CH(CH3)Br

  • C(CH3)3Cl

  • CH3CHBrCH2CH3 

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51 mark

Butanoic acid can be synthesised using the following two-step reaction scheme.

straight C subscript 4 straight H subscript 9 Br rightwards arrow with Step space 1 on top straight C subscript 4 straight H subscript 9 OH rightwards arrow with Step space 2 on top straight C subscript 3 straight H subscript 7 COOH

What is the correct classification of the steps?

  Step 1 Step 2
A Substitution  Addition
B Oxidation Substitution
C Addition Oxidation
D Substitution Oxidation

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61 mark

What reagents and conditions are required for the following two-step synthesis of propanal?

1-chloropropane rightwards arrow with Step space 1 on top Propan-1-ol rightwards arrow with Step space 2 on top Propanal

  Step 1 Step 2
A Reflux with NaOH (aq) Distil with K2Cr2O7 
B Reflux with NaCN (aq) Reflux with K2Cr2O7 / H+ 
C Distil with K2Cr2O7 / H+  Reflux with NaCN (aq)
D Reflux with NaOH (aq) Distil with K2Cr2O7 / H+ 

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71 mark

Butanone can be produced from but-1-ene by the following two-step synthesis of propanal.

But-2-ene rightwards arrow with Step space 1 on top INTERMEDIATE rightwards arrow with Step space 2 on top Butanone

Step 1 uses a phosphoric acid catalyst and steam.

What is the intermediate?

  • Butan-1-ol

  • Butan-2-ol

  • Butan-2,3-diol

  • Butanoic acid

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81 mark

The structure of a compound used to treat attention deficit hyperactivity disorder is shown below.

ocr-4-6m-q8

Which functional group(s) is / are in a molecule of the compound?

  1. Amine
  2. Carboxylic acid
  3. Ketone

  • 1, 2 and 3

  • Only 1 and 2

  • Only 2 and 3

  • Only 1

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91 mark

Ethane-1,2-diol can be made from ethene using the following two-stage synthetic route.

H2C=CH2 rightwards arrow with Step space 1 on top BrCH2CH2Br rightwards arrow with Step space 2 on topCH2OHCH2OH

What reagents are required for each step?

  Step 1 Step 2
A Excess HBr (aq)  Ethanolic NaOH
B Br2 (aq) C2H5OH (l)
C H2 (g) with a Ni catalyst NaOH (aq)
D Br2 (aq)  NaOH (aq)

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101 mark

Ethane-1,2-diol can be made from ethene using the following two-stage synthetic route.

H2C=CH2 rightwards arrow with Step space 1 on top BrCH2CH2Br rightwards arrow with Step space 2 on topCH2OHCH2OH

What are the mechanisms involved in each step?

  Step 1 Step 2
A Electrophilic substitution  Electrophilic addition
B Electrophilic addition Nucleophilic substitution
C Electrophilic addition Nucleophilic addition
D Nucleophilic substitution Electrophilic addition

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