Assignment: Questions on Topic 20.2: Synthetic routes
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Starting with 2-methylpropane deduce a synthetic pathway to make 2-methylpropanoic acid.
CH3CH(CH3)CH3 → CH3CH(CH3)COOH
For each step specify the reagents and any necessary conditions and write an equation for each step.
10 lines
Step 1: React with chlorine in ultra violet light and separate 1-chloro-2-methylpropane from any other chlorinated products.
CH3CH(CH3)CH3 + Cl2 → CH3CH(CH3)CH2Cl
Step 2: React 1-chloro-2-methylpropane with warm dilute aqueous sodium hydroxide solution to give 2-methylpropan-1-ol.
CH3CH(CH3)CH2Cl + NaOH → CH3CH(CH3)CH2OH + NaCl
Step 3: Oxidize 2-methylpropan-1-ol by refluxing with acidified potassium dichromate(VI) solution to give the required product
(via 2-methylpropanal).
CH3CH(CH3)CH2OH + H2O → CH3CH(CH3)COOH + 4H+ + 4e−
Design a synthetic route to make butanone starting with but-1-ene.
CH3CH2CHCH2 → CH3CH2COCH3
Knowing that the first step involves the addition of hydrogen bromide to but-1-ene state the name of the mechanism for the first two steps.
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Step 1: React but-1-ene with hydrogen bromide to form 2-bromobutane (formed in preference to 1-bromobutane according to Markovnikov’s rule).
Mechanism: Electrophilic addition.
Step 2: React 2-bromobutane with warm dilute aqueous sodium hydroxide solution to give butan-2-ol.
Mechanism: a mixture of S
N1 and S
N2.
Step 3: Oxidize butan-2-ol by refluxing with acidified potassium dichromate(VI) solution to give butanone.
You are provided with ethanal and any inorganic reagents and laboratory equipment you require but no other organic compounds. Design a method to synthesise ethyl ethanoate from ethanal.
CH3CHO → CH3COOC2H5
For each step specify the reagents and any necessary conditions.
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Step 1: Oxidize some of the ethanal by refluxing with acidified potassium dichromate(VI) solution to give ethanoic acid.
Step 2: Reduce the rest of the ethanal with sodium borohydride (or lithium aluminium hydride) to give ethanol.
Step 3: Warm the ethanol and the ethanoic acid formed in
Steps 1 and
2 in the presence of concentrated sulfuric acid to produce the desired ester.
Show how phenylamine can be synthesised from benzene.
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Step 1: Covert benzene into nitrobenzene by warming (keep below 50 oC) with a mixture of concentrated nitric acid and concentrated sulfuric acid.
Step 2: Reduce nitrobenzene to phenylamine by using tin and concentrated hydrochloric acid then react the phenylammonium chloride intermediate with sodium hydroxide solution.
Propyl ethanoate is used as a solvent and has the characteristic smell of pears.
Design a synthetic route to make propyl ethanoate starting from 1-chloropropane and chloroethane as the only organic compounds available.
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Step 1: React 1-chloropropane with warm dilute aqueous sodium hydroxide solution to give propan-1-ol.
Step 2: React chloroethane with warm dilute aqueous sodium hydroxide solution to give ethanol.
Step 3: Oxidize the ethanol obtained in Step 2 by refluxing with acidified potassium dichromate(VI) solution to ethanoic acid.
Step 4: React the ethanoic acid with the propan-1-ol obtained from Step 1 by warming in the presence of concentrated sulfuric acid to give the ester.