Industrial chemists are evaluating two competing industrial reaction pathways for the manufacture of methyl methacrylate (MMA, C5H8O2C_5H_8O_2C5H8O2, Mr=100.0M_r = 100.0Mr=100.0), an essential monomer used to produce acrylic plastics:
Pathway A (Acetone cyanohydrin route):
CH3COCH3+HCN+H2SO4+CH3OH→C5H8O2+NH4HSO4 CH_3COCH_3 + HCN + H_2SO_4 + CH_3OH \rightarrow C_5H_8O_2 + NH_4HSO_4 CH3COCH3+HCN+H2SO4+CH3OH→C5H8O2+NH4HSO4Pathway B (Propyne carbonylation route):
CH3C≡CH+CO+CH3OH→C5H8O2 CH_3C\equiv CH + CO + CH_3OH \rightarrow C_5H_8O_2 CH3C≡CH+CO+CH3OH→C5H8O2Which of the following statements correctly evaluates these pathways in terms of process improvement and green chemistry?
Pathway B has an atom economy of 100%100\%100% and avoids the use of highly toxic hydrogen cyanide (HCNHCNHCN), representing a significant improvement in process safety and sustainability.
Pathway A is more sustainable because the by-product ammonium bisulfate (NH4HSO4NH_4HSO_4NH4HSO4) is non-toxic and can be discharged directly into local waterways without environmental treatment.
Pathway A has an atom economy of 85.5%85.5\%85.5% because sulfuric acid (H2SO4H_2SO_4H2SO4) acts as a regenerable catalyst and is excluded from the atom economy calculation.
Pathway B has a lower atom economy than Pathway A because the carbon monoxide (COCOCO) reactant contains a triple bond which reduces the thermodynamic efficiency of the process.
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.