Question

Using your reaction roadmap as a guide, show how to convert 2 -methylbutane into racemic 3 -bromo-2-methyl-2-butanol. Show all reagents and all molecules synthesized along the way.

Short answer

Question: Outline the reaction pathway to convert 2-methylbutane into racemic 3-bromo-2-methyl-2-butanol. Answer: The reaction pathway involves two main steps: (1) Allylic Bromination using N-bromosuccinimide (NBS) and a radical initiator, resulting in the formation of 3-bromo-2-methylbutane, and (2) a nucleophilic substitution reaction (SN1) with water to replace the bromine atom with a hydroxyl group, generating racemic 3-bromo-2-methyl-2-butanol.

Step-by-step solution

Allylic Bromination

To introduce a bromine atom at the 3-position of 2-methylbutane, we perform allylic bromination using N-bromosuccinimide (NBS) and a radical initiator such as benzoyl peroxide (BPO) or azo-initiator like AIBN. The reaction mechanism involves the formation of a radical at an allylic position followed by the addition of a bromine atom, thus adding a bromine atom at the 3-position. The reaction will proceed as follows: 2-methylbutane + NBS + BPO (or AIBN) → 3-bromo-2-methylbutane #Step 2: Formation of racemic 3-bromo-2-methyl-2-butanol#

Formation of racemic 3-bromo-2-methyl-2-butanol

After obtaining 3-bromo-2-methylbutane, we need to replace the bromine atom at the 3-position with a hydroxyl group. This is achieved by performing a nucleophilic substitution reaction (SN1). In this case, the substrate, 3-bromo-2-methylbutane, gets solvolyzed and forms a carbocation. When the reaction is carried out in the presence of water, a hydroxyl group (-OH) attacks the carbocation, which results in the formation of 3-bromo-2-methyl-2-butanol. The reaction will proceed as follows: 3-bromo-2-methylbutane + H2O → racemic 3-bromo-2-methyl-2-butanol By performing these two steps, we can convert 2-methylbutane into racemic 3-bromo-2-methyl-2-butanol.