Question

Choose the member of the given pair that will react faster by $S_{N}1$ mechanism.
$1$-bromopropane or $2$-bromopropane

• A. $2$-bromopropane > $1$-bromopropane
• B. $2$-bromopropane < $1$-bromopropane
• C. $2$-bromopropane = $1$-bromopropane
• D. None of these

Answer 1

Answer: (A)

$2$-bromopropane > $1$-bromopropane

SN1–E1 reactions are most rapid with tertiary alkyl halides, they occur more slowly with secondary alkyl halides, and they are never observed with primary alkyl halides.

Reactivity of alkyl halides in $S_{N}1$ reactions:

tertiary >> secondary >> primary

Thus the order of reactivity

$2$-bromopropane > $1$-bromopropane