Order of nucleophilicity:

(i) ${\mathrm{OH}}^{-}$
(ii) ${\mathrm{HS}}^{-}$
(iii)$\mathrm{Ph}-{\mathrm{O}}^{-}$
(iv) ${\mathrm{C}}_2{\mathrm{H}}_5-{\mathrm{O}}^{-}$

The reaction.

is called?

For the following reaction:

(a) ${\mathrm{CH}}_3{\mathrm{CH}}_2{\mathrm{CH}}_2\mathrm{Br}+\mathrm{KOH}⟶{\mathrm{CH}}_3\mathrm{CH}={\mathrm{CH}}_2+\mathrm{KBr}+{\mathrm{H}}_2\mathrm{O}$

(b) ${\left({\mathrm{CH}}_3\right)}_2\mathrm{CH}-\mathrm{Br} + \mathrm{KOH} \to {\left({\mathrm{CH}}_3\right)}_2\mathrm{CH}-\mathrm{OH} + \mathrm{KBr}$

(c) 

Which of the following statements is correct?

The decreasing order of nucleophilicity among the nucleophiles

(A) ${\text{CH}}_3\underset{O}{\underset{\left|\right|}{\text{C}}}-{\text{O}}^{-}$

(B) ${\mathrm{CH}}_3{\mathrm{O}}^{-}$

(C)  ${\mathrm{CN}}^{-}$

(D) 

$2-$chloro$-2-$methylpentane on reaction with sodium methoxide in methanol yields :

The major product obtained in the following reaction is :

The increasing order of the reactivity of the following halides for the Snt reaction is :