Question

Which of the following sequence of reactions would
convert tertiary butyl alcohol into 3,3-dimethylbutan-1-ol?

• A. 1: $B{r}_2$ followed by Mg in Ether; 2: Oxirane 3: $H_3{O}^{+}$
• B. 1: HBr followed by Mg in Ether; 2: Oxirane 3: $H_3{O}^{+}$
• C. 1: HBr followed by Mg in Ether; 2: dioxane 3: $H_3{O}^{+}$
• D. None of the above

Answer 1

The correct option is B 1: HBr followed by Mg in Ether; 2: Oxirane 3: $H_3{O}^{+}$

The substrate is a tertiary alcohol with exactly 4 carbons whereas the required product is a primary alcohol but with 4 + 2 = 6 carbon atoms - 3,3-dimethylbutan-1-ol.
Somehow, two more carbon atoms need to be added; one of the ways is via a Grignard synthesis using ring opening of oxirane: