Help with hard chemistry alevel question

Four compounds, all colourless liquids are
.Butanoic acid
.butanal
.butanone
.2-methylpropan-2-ol

Two of these compounds can be identified using different test tube reactions
Describe these two test tube reactions by giving reagents and observations in each case
suggest how the result of infrared could be used to distinguish between the other compounds.[6 marks]

So there's an acid, an aldehyde, a ketone and a tertiary alcohol.
You can use sodium carbonate to distinguish the acid from the rest in the first test. Then you can oxidise the aldehyde (but not the ketone and tertiary alcohol) using another reagent to identify the aldehyde. You're left with the ketone and tertiary alcohol which you can distinguish because of the different bonds present.