Scottish Highers Chemistry Esters: Fusel oil is formed as a by-prod

Question

Fusel oil is formed as a by-product during the production of bioethanol for fuel. It is a mixture of several alcohols.

(a) The shortened structural formula of one of the alcohols contained in fusel oil is shown.

CH₃CH(CH₃)CH₂CH₂OH

State the name of this alcohol.

(b) Propan-1-ol is also found in fusel oil.

Propan-1-ol is reacted with an oxidising agent to produce propanal.

(i) Complete the ion-electron equation for the oxidation reaction.

C₃H₇OH → C₃H₆O + 2e⁻

(ii) Acidified potassium dichromate can be used as the oxidising agent and reacts as shown below.

Cr₂O₇²⁻(aq) + 14H⁺(aq) + 6e⁻ → 2Cr³⁺(aq) + 7H₂O(l)

Suggest why the potassium dichromate must be acidified.

(iii) State the colour change that would be observed when propan-1-ol reacts with acidified potassium dichromate.

(iv) The equation for the reduction of another oxidising agent that could be used to oxidise propan-1-ol is shown below.

Ag⁺(aq) + e⁻ → Ag(s)

Name the reagent that provides this oxidising agent.

(v) State why 2-methylbutan-2-ol cannot be oxidised using these oxidising agents.

(vi) In the reaction of butan-1-ol to butanal, oxidation can be identified by an increase in the oxygen to hydrogen ratio.

Complete the table to show the oxygen to hydrogen ratios in butan-1-ol and butanal.

Substance	Oxygen to Hydrogen Ratio
Butan-1-ol	1:10
Butanal	1:8

Fusel oil is formed as a by-product during the production of bioethanol for fuel - Scottish Highers Chemistry - Question 5 - 2022