Question 8.2: How might you prepare the following alcohol?
Synthesizing an Alcohol
How might you prepare the following alcohol?
S t r a t e g y
Problems that require the synthesis of a specific target molecule should always be worked backward. Look at the target, identify its functional group(s), and ask yourself, “What are the methods for preparing that functional group?” In the present instance, the target molecule is a secondary alcohol (R_2CHOH) and we’ve seen that alcohols can be prepared from alkenes by either hydroboration–oxidation or oxymercuration–demercuration. The –OH bearing carbon in the product must have been a double-bond carbon in the alkene reactant, so there are two possibilities: 4-methylhex-2-ene and 3-methylhex-3-ene
4-Methylhex-2-ene has a disubstituted double bond, RCH=CHR′, and will probably give a mixture of two alcohols with either hydration method since Markovnikov’s rule does not apply to symmetrically substituted alkenes. 3-Methylhex-3-ene, however, has a trisubstituted double bond and should give only the desired product on non-Markovnikov hydration using the hydroboration–oxidation method.
