A LevelChemistryOCRExam Questions6. Organic Chemistry & AnalysisBenzene & Aromatic Compounds

Benzene & Aromatic Compounds (OCR A Level Chemistry A): Exam Questions

Exam code: H432

3 hours31 questions

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Benzene & Aromatic Compounds

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1
1 mark

What are the reagents required for the conversion of benzene to nitrobenzene?

  • Hydrogen gas in presence of nickel catalyst

  • Concentrated nitric acid and concentrated hydrochloric acid

  • Concentrated sulfuric acid and concentrated nitric acid

  • Tin with concentrated hydrochloric acid

Choose your answer

2
1 mark

Cyclohexene is an unsaturated hydrocarbon and can undergo hydrogenation as shown

Hydrogenation of Cyclohexene

The expected value for the enthalpy value for the hydrogenation of benzene is -360 kJ mol-1. The actual value for the reaction is -208 kJ mol-1.

Which is the correct explanation?

  • The s orbitals overlap to produce a stable structure

  • The bond length of the C=C bonds are shorter than the C-C bonds

  • Delocalisation of electrons in the benzene ring increases the stability

  • Each carbon in benzene has three covalent bonds

Choose your answer

3
1 mark

Which product is formed when benzene, C6H6, reacts with ethanoyl chloride, CH3COCl, in the presence of aluminium chloride, AlCl3?

  • C6H6COCH3

  • HCl

  • C6H5CH3CO

  • C6H5CH2CH3

Choose your answer

4
1 mark

Which of the following statements about phenol is not correct? 

  • Phenol behaves as a weak acid 

  • Phenol reacts with bromine to form an orange precipitate 

  • The formula for the phenoxide ion is C6H5O-

  • Phenol reacts with sodium to form hydrogen gas

Choose your answer

5
1 mark

Which part of the following mechanism is not correct?

1-4

How did you do?

1
1 mark

Which of the following explains why the enthalpy of hydrogenation of benzene is lower than expected?

  • The overlap of p-orbitals allows electrons to become delocalised

  • Benzene contains both single and double bonds

  • The carbon-carbon bond lengths in benzene are shorter than a carbon-carbon single bond

  • Benzene contains sp2 hybridised carbon atoms

Choose your answer

2
1 mark

Benzene can undergo nitration to form nitrobenzene. Which of the following statements is not correct?

  • Concentrated nitric acid acts as a base

  • A nitronium ion acts as an electrophile

  • HSO4- is produced in the formation of the electrophile

  • Aluminum chloride is required as a catalyst for the reaction

Choose your answer

3
1 mark

Which statement about the reactions of benzene is correct?

  1. The delocalised system in benzene will repel attack from a nucleophile

  2. During electrophilic substitution, the electrophile attacks the delocalised electrons in the benzene ring

  3. NH3 is not a strong enough nucleophile to undergo nucleophilic substitution with benzene

  • 1, 2, and 3

  • Only 1 and 2

  • Only 2 and 3

  • Only 1

Choose your answer

4
1 mark

The following compound can be synthesised from benzene. 

ocr-a2-6-1m-mcq-q4-phenylpropanone---compound-b

Which reagent is required for this conversion?

  • CH3CH2COOH

  • CH3CH2CH2Cl

  • CH3CH2COCl 

  • CH3CH2CHO

Choose your answer

5
1 mark

Which one of the following can react with propanoic acid and with phenol?

  • Bromine

  • Ethanol and concentrated sulfuric acid

  • Sodium hydrogen carbonate 

  • Aqueous sodium hydroxide 

Choose your answer

1
1 mark

Which statements is/are evidence for the modern day model of benzene?

  1. The enthalpy of hydrogenation of benzene is less exothermic than the theoretical value for 'cyclohexatriene'.

  2. All carbon-carbon bond lengths in benzene are identical and intermediate in length between a single C–C and a double C=C bond.

  3. Benzene is a planar molecule with C–C–C bond angles of 120°.

  • 1, 2 and 3

  • Only 1 and 2

  • Only 2 and 3

  • Only 1

Choose your answer

2
1 mark

Which statement is not correct?

  • Nitrobenzene has reduced electron density so is less reactive than benzene. 

  • Increased electron density at positions 2, 4 and 6 of aminobenzene promotes substitution at these positions. 

  • Nitrobenzene has reduced electron density at positions 3 and 5. 

  • Phenol is more reactive than benzene and is a weak acid. 

Choose your answer

3
1 mark

A multi-step mechanism is shown below.

xdHcPPSI_ocr-a2-6-1h-mcq-q3-reaction-sequence

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

  • Step 1: concentrated HNO3 and concentrated H2SO4

  • Step 2: Sn and HCl

  • Step 3: Cl2

  • Step 4: AlCl3 and CH3COCl

Choose your answer

4
1 mark

Molecule X is shown below.

v3M1_VGF_ocr-a2-6-1h-mcq-q4-molecule-x

                  

Which statement(s) is/ are correct?

  1. An electrophile reacts with benzene to produce molecule X. The electrophile is formed from AlCl3 and ClCH2COCl.

  2. Molecule X has an isomer that exhibits optical activity and when added to Tollens’ reagent produces a silver mirror.

  3. Molecule X will produce steamy white fumes when added to water at room temperature.

  • 1, 2 and 3

  • Only 1 and 2

  • Only 2 and 3

  • Only 1

Choose your answer

5
1 mark

TNT (2,4,6-trinitromethylbenzene) is formed from methylbenzene in a reaction with a yield of 57.0 %. What mass of TNT is formed from 6.00 g of methylbenzene?

  • 1.39 g

  • 8.44 g

  • 25.2 g

  • 26.0 g

Choose your answer

6
1 mark

Which row correctly describes the mechanism and the type of bond fission involved when benzene reacts with a mixture of concentrated nitric acid and concentrated sulfuric acid?

Mechanism type

Bond fission during electrophile generation

A

Nucleophilic substitution

Heterolytic

B

Electrophilic substitution

Homolytic

C

Electrophilic substitution

Heterolytic

D

Electrophilic addition

Heterolytic

    Choose your answer