The reactivity of alkyl bromides towards iodide ion in dry acetone decreases in the order:
$I. CH_3CH_2Br$
$II. CH_3-CH(CH_3)-Br$
$III. CH_3-C(CH_3)_2-Br$
$IV. CH_3Br$

Which of the two stereoisomers of $4-t-$butylcyclohexyl iodide $(^{127}I^-)$ will undergo $S_N2$ substitution with $^{128}I^-$ faster,and why?

Arrange the following compounds in order of decreasing rate of hydrolysis for $S_{N}1$ reaction:
$(I) \ C_6H_5-CH_2-Br$
$(II) \ p-CH_3-C_6H_4-CH_2-Br$
$(III) \ p-CH_3CH_2-C_6H_4-CH_2-Br$
$(IV) \ p-(CH_3)_2CH-C_6H_4-CH_2-Br$

Which of the following processes does $NOT$ occur during the preparation of $CHCl_3$ from $C_2H_5OH$ and bleaching powder?

The correct order of the rate of reaction of the following reactants with a nucleophile by $S_{N}1$ mechanism is:
(Given: Structure $I$ and $II$ are rigid)

Given below are two statements:
Statement $I$: $(CH_3)_3C-CH_2-Cl$ will undergo $S_N1$ reaction even though it is a primary halide.
Statement $II$: It will not undergo $S_N2$ reaction very easily even though it is a primary halide.
In the light of the above statements, choose the most appropriate answer from the options given below: