Chemistry 9701 · AS & A Level · Analytical techniques

Analytical techniques — practice question

Organic compounds may be told apart by means of chemical tests and analytical techniques.
(a(i))[8]

Complete Table 3.1 so that you: identify a reagent that can tell the compounds in each pair apart; give the positive outcome of the chemical test and state which compound gives that outcome. Use a different reagent for each test.

(a(ii))[1]

$A1$ and $A2$ are structural isomers. Define what is meant by structural isomers.

(a(iii))[1]

Give the systematic name for $B2$.

(a(iv))[1]

Deduce the molecular formula for $D1$.

(b(i))[1]

$D2$ forms polymer $Z$ when heated gently. Identify the type of polymer formed from $D2$.

(b(ii))[2]

Draw a single repeat unit of polymer $Z$.

(c)

Organic compound $E$ contains three carbon atoms. When $E$ reacts with cold dilute acidified $\text{KMnO}_4\text{(aq)}$, a single compound $F$ is formed and has $M_r = 154.9$. Fig. 3.1 gives the infrared spectrum of $E$. Fig. 3.2 gives the infrared spectrum of $F$.

(c(i))[1]

Use the two infrared spectra and Table 3.2 to identify the functional group that is found only in E. Justify your answer by referring only to absorptions at frequencies above $1500\ \text{cm}^{-1}$.\n\nfunctional group identified ........................................................\n\nexplanation ................................................................................................................................

(c(ii))[1]

Use the infrared spectrum of $F$ to identify the functional group formed when $E$ reacts with cold dilute acidified $\text{KMnO}_4\text{(aq)}$. Justify your answer, referring only to absorptions at frequencies greater than $1500\ \text{cm}^{-1}$.\n\nfunctional group identified ........................................................\n\nexplanation ................................................................................................................................

(c(iii))[1]

The mass spectrum of E has a molecular ion peak and an M+2 peak with approximately equal abundance at $m/e = 120$ and $122$. Deduce the relative molecular mass, $M_r$, of E.

(c(iv))[1]

Use the information from 3(c) to suggest a structure for E.

(c(v))[1]

Complete the equation for the reaction of E with cold dilute acidified $\text{KMnO}_4\text{(aq)}$ to form F. In the equation, $[O]$ stands for cold dilute acidified $\text{KMnO}_4\text{(aq)}$.\n\n$\text{H}_2\text{O} + [O] + \ldots \rightarrow \ldots$

(d)[3]

C2 can be made from A1 using a single organic reactant. Devise a multistep synthetic route from A1 to C2. Identify the appropriate reagents and conditions, and state the organic product formed in each step.

Worked solution & mark scheme

This 22-mark question has a full step-by-step worked solution and mark scheme. One marking point: A correct reagent, for example Tollens’, Fehling’s, $\mathrm{K_2Cr_2O_7}$ or $\mathrm{KMnO_4}$

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