Using chemical reagents in test tubes, distinguish between isomers: A CH3CO(CH2)2CHOH, B CH3CH(OH)(CH2)2CHO and C C(CH3)2OHCOCH3

Answer:

*First draw out each compounds' structural formula (an image of the "shape and arrangement of the atoms in space"), then identify all functional groups in each compound.

*Add Tollens' reagent to all three, the compound which provides a silver mirror / precipitate, is compound B. This is because B is the only one to have an aldehyde group, which is oxidised by Tollens and gives a positive result. Ketones are NOT oxidised by Tollens and so give a negative result (no mirror).

*Next, add acidified potassium dichromate, formula Cr₂O₇^2-, to all three. A and B give a positive result for this test, a colour change from orange to green, as they both have either primary or secondary alcohols. C gives a negative result, no colour change, as it has a tertiary alcohol which won't be oxidised by the dichromate.

So:

Tollens = X, Cr₂O₇ = ✓ -> Compound A

Tollens = ✓ -> Compound B

Tollens = X, Cr₂O₇ = X -> Compound C