Final answer:
To prepare RR' R'' OH, a suitable Grignard reagent can react with an aldehyde or a ketone.
Step-by-step explanation:
In order to prepare RR' R'' OH, we can use the action of excess of a suitable Grignard reagent on an aldehyde or a ketone.
For example, if we react a Grignard reagent (R-Mg-Br) with an aldehyde (R'-CHO), we can obtain the desired product RR' R'' OH.
The reaction can be represented as: R-Mg-Br + R'-CHO -> RR' R'' OH + MgBr2.