Question

Consider the given reactions:

$\left(I\right){Me}_{3}C-F\underset{}{\overset{H_{2}O/H^{\oplus }}{\to }}{Me}_{3}C-OH$
$\left(II\right){Me}_{3}C-F\underset{}{\overset{\stackrel{\ominus }{O}H}{\to }}{Me}_{3}C-OH$
$\left(III\right){Me}_{3}C-Cl\underset{}{\overset{\stackrel{\ominus }{O}H}{\to }}{Me}_{3}C-OH$
$\left(IV\right){Me}_{3}C-\stackrel{Me|}{\underset{|Me}{C}}-Cl\underset{}{\overset{\stackrel{\ominus }{O}H}{\to }}{Me}_{3}C-\stackrel{Me|}{\underset{|Me}{C}}-OH$
Which of the statements are correct?

• A. Reaction $\left(I\right)$ is faster than $\left(II\right)$
• B. Reaction $\left(II\right)$ is faster than $\left(I\right)$
• C. Reaction $\left(III\right)$ is faster than $\left(IV\right)$
• D. Reaction $\left(IV\right)$ is faster than $\left(III\right)$

Answer 1

Answer: (A), (D)

The correct options are
A Reaction $\left(I\right)$ is faster than $\left(II\right)$
D Reaction $\left(IV\right)$ is faster than $\left(III\right)$

Although $F^{\ominus }$ is a poor leaving group, in acidic condition, $F$ forms H-bonding and its departure is easier. So, in acidic medium, reaction $\left(I\right)$ is solvolysed faster than $\left(II\right)$.
This is an example of electrophilic catalysts.
ii. The formation of ${Me}_{3}C-\stackrel{Me|}{\underset{|Me}{C^{\oplus }}}$ from $\left(IV\right)$ reduces some of th steric hinderance or crowding in reactant in $\left(IV\right)$, induced by the two $\left(Me\right)$ groups and the t-$Bu$ on teh $\alpha$C-atom. This is an example of steric acceleration.
Moreover, carbocation is further stabilised bu $+I$ effect of two $\left(Me\right)$ groups and t-$Bu$ groups.

So, reaction $\left(IV\right)$ is faster than $\left(III\right)$