Complete the table to show the observations when an aqueous solution of glycolic acid is added separately to each reagent. If a reaction takes place, name the functional group in glycolic acid that is responsible. The reagents are $\text{Na}_2\text{CO}_3(\text{aq})$, 2,4-DNPH, and acidified $\text{Cr}_2\text{O}_7^{2-}$.
Two routes for making glycolic acid are shown. Sequence A: $\text{HCHO} \\ \xrightarrow[{\text{HCN and NaCN}}]{\text{reaction 1}} X \\ \xrightarrow[ ]{\text{reaction 2}} \\ \text{CH}_2(\text{OH})\text{CO}_2\text{H}$. Sequence B: $\text{CH}_3\text{CO}_2\text{H} \\ \xrightarrow[ ]{\text{Br}_2, \text{reaction 3}} \\ \\ \text{CH}_2\text{BrCO}_2\text{H} \\ \xrightarrow[ ]{\text{reaction 4}} \\ \\ \text{CH}_2(\text{OH})\text{CO}_2\text{H}$. Draw the structure of $X$.
Name the reagent used in reaction 2.
Name the mechanism for reaction 3.
Suggest the essential condition for reaction 3.
Reaction 4 proceeds through an $\text{S}_\text{N}2$ mechanism. Complete the mechanism diagram for reaction 4. Include every relevant charge, partial charge, curly arrow and lone pair.
State the role played by $\text{NaBH}_4$ in this reaction.
Write the equation for this reaction in molecular formulae. Use $[\text{H}]$ to stand for $\text{NaBH}_4$.
The infra-red spectrum of $Y$ is shown. State one way in which this spectrum differs from the infra-red spectrum of glycolic acid. Explain your answer with specific reference to the peaks in the range $1500$-$4000\ \text{cm}^{-1}$.
Suggest a structure for $Y$.