# How can you identify aldehydes and ketones?

Both simple ketones and aldehydes have the ONE DEGREE of unsaturation...i.e. they have formula ${C}_{n} {H}_{2 n} O$ RATHER than ${C}_{n} {H}_{2 n + 2} O$. In general, aldehydes ARE MORE reactive than ketones. And this differential reactivity mirrors the differential reactivity of ${1}^{\circ}$ alkyl halides compared to ${2}^{\circ}$ alkyl halides as electrophilic substrates.