Chemistry 9701 · AS & A Level · Analytical techniques

Analytical techniques — practice question

Compound F is a carboxylic acid.
(a)[1]

Compound F has $31.4\%$ oxygen by mass, and its mass spectrum shows a molecular ion peak at $m/e = 102$. Use every piece of this information to show that the molecular formula of compound F is $\text{C}_5\text{H}_{10}\text{O}_2$. Show all your working.

(b(i))[2]

The first isomer has already been drawn. Draw the skeletal formulae of the three remaining structural isomers.

(b(ii))[1]

State the systematic name of isomer 1.

(c(i))[1]

F is one of the four structural isomers in (b)(i). A carbon-13 NMR spectrum of F is shown. Use the spectrum to identify isomer F. Draw its structure in the box below.

(c(ii))[2]

Use the Data Booklet together with your knowledge of carbon-13 NMR spectroscopy to identify the environments and hybridisations of the carbon atoms responsible for the three absorptions at $\delta = 27\,\text{ppm}$, $41\,\text{ppm}$ and $179\,\text{ppm}$.

(d(i))[4]

G is another one of the four structural isomers in (b)(i). The proton NMR spectrum of G is shown. Use the Data Booklet and the spectrum to complete the table below. The actual chemical shifts for the four absorptions in G and the splitting pattern at $\delta = 1.6\,\text{ppm}$ have been supplied for you.

(d(ii))[1]

Deduce which isomer is G and draw its structure in the box.

(e)[1]

Name or give the formula of a suitable solvent for obtaining a proton NMR spectrum.

Worked solution & mark scheme

This 13-mark question has a full step-by-step worked solution and mark scheme. One marking point: Working that gives the $C_4H_9$ fragment, or an equivalent argument.

  • Full mark scheme, point by point
  • Step-by-step worked solution
  • Write your answer & get it marked instantly by AI