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Organic chemistry

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Question 45

Ethanol is a highly versatile chemical intermediate manufactured on an industrial scale using two distinct pathways:

  • Method 1: Anaerobic fermentation of aqueous glucose solutions.
  • Method 2: Direct catalytic hydration of ethene.
a.

State the catalyst used in each method.

  • Method 1:
  • Method 2:
[2]
b.

Two chemical manufacturing firms, Company A and Company B, produce industrial ethanol. Information regarding their operations is summarized below:

Company ACompany B
Operational ContextSituated in a region with extensive agricultural cultivation of sugar beet.Situated in an industrial zone adjacent to a major oil refinery and steam cracker.
End-use of EthanolLow-grade additive for domestic biofuel blends.Ultra-pure solvent for high-precision electronic component cleansing.

Identify which method of production each company is more likely to utilize, and justify your choices.

[4]
c.

Alkenes are highly valuable starting materials. While traditionally produced via the thermal cracking of crude oil fractions, they can also be synthesized from alcohols.

One of the polymers synthesized from but-1-ene is poly(but-1-ene). Complete the equation to show the formation of poly(but-1-ene) from but-1-ene:

nHH∣∣C=C∣∣HCH2CH3⟶… n \begin{array}{cc} \text{H} & \text{H} \\ | & | \\ \text{C} & \hspace{-0.5em}=\text{C} \\ | & | \\ \text{H} & \text{CH}_2\text{CH}_3 \end{array} \longrightarrow \dots nH∣C∣H​H∣=C∣CH2​CH3​​⟶…
[1]
d.

A heavy hydrocarbon fraction obtained from crude oil consists of hexadecane, C16H34\text{C}_{16}\text{H}_{34}C16​H34​. Complete the equation to show the thermal cracking of one molecule of C16H34\text{C}_{16}\text{H}_{34}C16​H34​ to yield two molecules of propene and one molecule of another hydrocarbon:

C16H34⟶2C3H6+… \text{C}_{16}\text{H}_{34} \longrightarrow 2\text{C}_3\text{H}_6 + \dots C16​H34​⟶2C3​H6​+…
[1]
e.

Explain why it may become essential in the future to produce alkenes via the dehydration of plant-derived ethanol rather than through the cracking of crude oil.

[2]
Markscheme

Organic chemistry Questions

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