Chemistry 9701 · AS & A Level · Polymerisation

Polymerisation — practice question

By using a variety of modern spectroscopic methods, astronomers have detected evidence of many molecules, ions and free radicals in dust clouds in Space. Many of these species have also been made in laboratories on Earth.
(a(i))[3]

Dicarbon monoxide may be prepared in a laboratory, and its analysis shows the atoms are arranged carbon-carbon-oxygen with no unpaired electrons, although one atom has only six electrons around it. Draw a dot-and-cross diagram for $\text{C}_2\text{O}$ and predict the shape of the molecule.

(a(ii))[1]

What does the term free radical mean?

(a(iii))[1]

Explain why $\text{NH}_2$ is called a free radical.

(b(i))[1]

Draw the structural formula of the polymer made from acrylonitrile, showing two repeat units.

(b(ii))[1]

What kind of polymerisation is this reaction?

(c(i))[1]

Suggest the structural formula of the organic compound Z formed by isomerisation of vinyl alcohol.

(c(ii))[1]

Suggest the structural formula of another isomer of vinyl alcohol that has a cyclic (ring) structure.

(d)[4]

Acrolein (2-propenal), $\text{CH}_2\text{=CHCHO}$, has also been detected in Space. Write the structural formulae of the organic compounds formed when acrolein is reacted separately with each of the following reagents:\n\n$\text{Br}_2$ in an inert solvent; $\text{NaCN}$ + dilute $\text{H}_2\text{SO}_4$; Tollens’ reagent; $\text{NaBH}_4$.

Worked solution & mark scheme

This 13-mark question has a full step-by-step worked solution and mark scheme. One marking point: “C-C-O in the correct sequence, with a linear arrangement” …

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