Outline a chemical test that can be performed to confirm the presence of a carbonyl group in an unknown sample. Explain how the crystalline product of this reaction can be used to determine the exact identity of the carbonyl compound, without using any spectroscopic methods.

Outline a chemical test, including the reagent and the expected observations, that can distinguish an aldehyde from a ketone.

A chemist is investigating two isomeric carbonyl compounds, F and G.

Elemental analysis shows that both compounds have the following percentage composition by mass: $C:69.77\%$; $H:11.63\%$; $O:18.60\%$

In their mass spectra:

• Compound F has a molecular ion peak at $m/z=86$ and a prominent fragment peak at $m/z=43$.
• Compound G has a molecular ion peak at $m/z=86$ and a prominent fragment peak at $m/z=57$.

Analyse this information to determine the empirical and molecular formulas. Deduce the structures of both compounds F and G, identifying the formulas of the fragment ions responsible for the peaks at $m/z=43$ and $m/z=57$ respectively. Draw the structural formula for each compound.

An organic compound H contains only carbon, hydrogen, and oxygen, and has a relative molecular mass ($M_r$) of $128.0$. Compound H contains two carbonyl groups and has no other functional groups.

The ${}^{1}H$ NMR spectrum of H contains the following signals:

• A singlet at $\delta =2.1ppm$ (relative peak area = 6)
• A triplet centred at $\delta =2.4ppm$ (relative peak area = 4)
• A pentet (quintet) centred at $\delta =1.8ppm$ (relative peak area = 2)

Analyse this spectrum to suggest a possible structure for compound H. Show all your reasoning, explaining how each NMR signal relates to the structure.