14. Hydrocarbons
A section of Chemistry, 9701
Listing 10 of 313 questions
Benzene, C6H6, can be obtained from crude oil. Benzene reacts with bromine, in the presence of a suitable catalyst, forming bromobenzene as one product. Give the name or formula of the other product of this reaction. In the presence of the catalyst, bromine can be considered to form the electrophile Br+. Complete the mechanism by which benzene reacts with Br+, using curly arrows to show the movement of electron pairs. intermediate Br Br+ + H+  Name this mechanism. Benzene can be used as a starting material in the synthesis of cyclohexylmethanol, C6H11CH2OH, as outlined below. benzene A CH2CH3 step 1 step 3 step 2 cyclohexylmethanol CH2OH CH2OH step 4 KMnO4 + OH–heat Identify a suitable reagent and a suitable catalyst for step1. reagent catalyst  Draw the structure of A. A  Identify suitable reagents for steps3 and 4. step 3 step 4  Deduce the number of peaks in the carbon‑13 NMR spectrum of cyclohexylmethanol. 
9701_w20_qp_41
THEORY
2020
Paper 4, Variant 1
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Describe the structure of a benzene molecule, C6H6. Your answer should include: ● the shape of the molecule ● the relative lengths of the C–C bonds ● bond angles ● the hybridisation of the carbon atoms ● the overlap between orbitals that produces each type of bond present. Benzene can be used as a starting material to produce phenylamine by a two-step synthesis. benzene nitrobenzene phenylamine NO2 NH2 step 1 step 2 Step1 is the reaction of benzene with NO2 + ions. Complete the mechanism and draw the intermediate of step1. Include all relevant charges and curly arrows to show the movement of electron pairs. intermediate nitrobenzene + H+ +NO2  State the name of the mechanism in . Identify the reagents needed to produce NO2 + ions. Write an equation to explain how these reagents produce NO2 + ions. Give reagents and conditions for the production of phenylamine from nitrobenzene in step2. Phenylamine reacts with Br2. Write an equation for this reaction. You may use structural or displayed formulae. Name the organic product of this reaction. Describe two observations that can be seen when phenylamine reacts with Br2. observation 1 observation 2  Describe the relative basicities of ammonia, ethylamine and phenylamine, starting with the least basic. Explain your answer in terms of their structures. least basic most basic  1,3‑diaminopropane, H2NCH2CH2CH2NH2, can be used to make polyamides. Identify one compound that would react with 1,3‑diaminopropane to form a polyamide. Draw a section of the polymer chain formed from 1,3‑diaminopropane and the compound you chose in . Your answer should: ● include four monomer residues (two of each type of monomer) ● show the amide link fully displayed ● clearly identify one repeat unit of this polymer.  
9701_w20_qp_42
THEORY
2020
Paper 4, Variant 2
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Benzene, C6H6, can be obtained from crude oil. Benzene reacts with bromine, in the presence of a suitable catalyst, forming bromobenzene as one product. Give the name or formula of the other product of this reaction. In the presence of the catalyst, bromine can be considered to form the electrophile Br+. Complete the mechanism by which benzene reacts with Br+, using curly arrows to show the movement of electron pairs. intermediate Br Br+ + H+  Name this mechanism. Benzene can be used as a starting material in the synthesis of cyclohexylmethanol, C6H11CH2OH, as outlined below. benzene A CH2CH3 step 1 step 3 step 2 cyclohexylmethanol CH2OH CH2OH step 4 KMnO4 + OH–heat Identify a suitable reagent and a suitable catalyst for step1. reagent catalyst  Draw the structure of A. A  Identify suitable reagents for steps3 and 4. step 3 step 4  Deduce the number of peaks in the carbon‑13 NMR spectrum of cyclohexylmethanol. 
9701_w20_qp_43
THEORY
2020
Paper 4, Variant 3
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