SolutionsNucleophilic Substitution
1. Hydroxide or acetate
We want to obtain 2-butanol from 2-bromobutane. What happens if it is treated with NaOH? What alternative would you propose?
With NaOH, a strong base, and a secondary substrate, SN2 and E2 compete: a lot of butene is obtained. It is better to treat it with potassium acetate in DMF (a good nucleophile and a very weak base: SN2) and then saponify the 2-butyl acetate with aqueous NaOH.
2. Tertiary halides
What is obtained when 2-bromo-2-methylpropane is treated with water? And with NaOH?
With water, a mixture of 2-methyl-2-propanol (SN1) and 2-methylpropene (E1). With NaOH, mainly 2-methylpropene by E2.
3. Latent function
What does it mean that the OH group is “latent” in the ester formed in the first step?
That the oxygen of the future alcohol is already bonded to the carbon, but as part of an ester. In the second step (saponification) the carboxylate leaves and the OH group is released.