Suggest the mechanism of the following reaction:

${\mathrm{CH}}_3 - {\mathrm{CH}}_2\mathrm{OH} \stackrel{\mathrm{HCl}}{\to }{\mathrm{CH}}_2-{\mathrm{CH}}_2-\mathrm{Cl}$

Suggest the mechanism of the following reaction,

Suggest the mechanism of the following reaction,

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The reaction of cyclopentyl bromide with sodium cyanide to give cyclopentyl cyanide proceeds faster, if a small amount of sodium iodide is added to the reaction mixture. Can you suggest a reasonable mechanism to explain the catalytic function of sodium iodide?

Suggest the mechanism whether ${\mathrm{S}}_{\mathrm{N}}1$ or ${\mathrm{S}}_{\mathrm{N}}2$ in the following reactions:

${\mathrm{CH}}_3{\mathrm{CH}}_2{\mathrm{CH}}_2\mathrm{X}\stackrel{\mathrm{Z}}{\to }{\mathrm{CH}}_3\mathrm{CH}\left(\mathrm{Z}\right){\mathrm{CH}}_3$

Suggest the mechanism whether ${\mathrm{S}}_{\mathrm{N}}1$ or ${\mathrm{S}}_{\mathrm{N}\hspace{0.17em}}2$ in the following reactions:

$\left({\mathrm{CH}}_3{)}_2\mathrm{CHCH}\right(\mathrm{X}){\mathrm{CH}}_3 \stackrel{\mathrm{Z}}{\to } ({\mathrm{CH}}_3{)}_2\mathrm{C}\left(\mathrm{Z}\right){\mathrm{CH}}_2{\mathrm{CH}}_3$

Suggest the mechanism whether ${\mathrm{S}}_{\mathrm{N}}1$ or ${\mathrm{S}}_{\mathrm{N}}2$ in the following reactions:

$({\mathrm{CH}}_3{)}_3{\mathrm{CCH}}_2\mathrm{Br} \stackrel{{\mathrm{C}}_2{\mathrm{H}}_5\mathrm{O}}{\to } ({\mathrm{CH}}_3{)}_3{\mathrm{CCH}}_2{\mathrm{OC}}_2{\mathrm{H}}_5$

Suggest the mechanism whether ${\mathrm{S}}_{\mathrm{N}}1$ or ${\mathrm{S}}_{\mathrm{N}}2$ in the following reactions: