Question

Among the choices of an alkyl bromide, the least reactive bromide in $S_{N}2$ reaction is:

• A. 1-bromopentane
• B. 2-bromo-2-methylbutane
• C. 1-bromo-3-methylbutane
• D. 1-bromo-2-methylbutane

Answer 1

The correct option is B 2-bromo-2-methylbutane

The order of reactivity of alkyl halides is $1^{\circ }>2^{\circ }>3^{\circ }$

The order pf reactivity follows this particular order because as the crowding the actual C - X bond increases, the steric inhibition increases. This decreases the reactivity in $S_{N}2$ reaction.

Therefore the least active bromide is 2-bromo-2-methylbutane.