An industrial chemist is evaluating two different production routes for ethyl ethanoate (CH3COOC2H5\text{CH}_3\text{COOC}_2\text{H}_5CH3COOC2H5, Mr=88.0M_r = 88.0Mr=88.0) to improve the overall sustainability of the manufacturing process.
Route A (Direct Addition):
CH3COOH+C2H4→CH3COOC2H5 \text{CH}_3\text{COOH} + \text{C}_2\text{H}_4 \rightarrow \text{CH}_3\text{COOC}_2\text{H}_5 CH3COOH+C2H4→CH3COOC2H5The ethene (C2H4\text{C}_2\text{H}_4C2H4, Mr=28.0M_r = 28.0Mr=28.0) is obtained from the steam cracking of crude oil fractions.
Route B (Esterification):
CH3COOH+CH3CH2OH⇌CH3COOC2H5+H2O \text{CH}_3\text{COOH} + \text{CH}_3\text{CH}_2\text{OH} \rightleftharpoons \text{CH}_3\text{COOC}_2\text{H}_5 + \text{H}_2\text{O} CH3COOH+CH3CH2OH⇌CH3COOC2H5+H2OThe ethanol (CH3CH2OH\text{CH}_3\text{CH}_2\text{OH}CH3CH2OH, Mr=46.0M_r = 46.0Mr=46.0) is obtained via the fermentation of agricultural crops. The formula mass of ethanoic acid (CH3COOH\text{CH}_3\text{COOH}CH3COOH) is 60.0.
Which statement correctly compares the sustainability and atom economy of these two chemical processes?
Route A is more sustainable overall because it achieves 100%100\%100% atom economy, whereas Route B has an atom economy of only 58.3%58.3\%58.3% due to the greenhouse gases released during fermentation.
Route B has an atom economy of 83.0%83.0\%83.0% and can be more sustainable in terms of raw materials because it utilizes ethanol derived from renewable crops, whereas Route A relies on ethene derived from finite crude oil resources.
Route A is less sustainable because its atom economy is 31.8%31.8\%31.8% due to the high mass of the ethene reactant, whereas Route B has a 100%100\%100% atom economy because the water produced can be recycled.
Route B is more sustainable because it has an atom economy of 17.0%17.0\%17.0%, which minimizes the energy required to heat the reaction mixture, whereas Route A has a 100%100\%100% atom economy which causes runaway exothermic reactions.
81 exam-style questions on OCR GCSE Chemistry Improving processes and products. Each one has a worked solution and a mark scheme showing where the marks go.