# How would you convert an aldehyde to a ketone?

$i . R - C \left(= O\right) H + R ' - M g B r \rightarrow R C \left(- O M g B r\right) R '$
$i i . R - C H \left(O M g B r\right) R ' + {H}_{2} O \rightarrow R - C H \left(O H\right) R ' + M g B r O H$
$i i i . R - C H \left(O H\right) R ' + \left[O\right] \rightarrow R C \left(= O\right) R '$
The electrophilic aldehyde will react with a Grignard or lithium reagent to give a new $C - C$ bond and (after workup) a secondary alcohol. The secondary alcohol can be easily oxidized by various means to give a ketone.