Overall reactions can be represented as :

The reaction is electrophilic substitution reaction.

The dehalogenation of vicinal tetrahaloalkane gives alkynes. It is done by heating the compound with $$Zn$$  dust.
\[\underset{\begin{smallmatrix} \text{1, 1, 2, 2-tetrachloropropane} \\ \text{Molecular weight = 182 } \end{smallmatrix}}{\mathop{C{{H}_{3}}\underset{\begin{smallmatrix} | \\ Cl\, \end{smallmatrix}}{\overset{\begin{smallmatrix} \,Cl \\ | \end{smallmatrix}}{\mathop{-\,\,C\,\,-}}}\,\underset{\begin{smallmatrix} |\,\,\,\,\,\, \\ Cl\,\,\,\,\,\, \end{smallmatrix}}{\overset{\begin{smallmatrix} Cl\,\,\, \\ |\,\,\,\,\, \end{smallmatrix}}{\mathop{CH}}}\,\xrightarrow{Zn/\Delta }}}\,\]      \[\underset{\text{Propyne}}{\mathop{C{{H}_{3}}-C\equiv C-H}}\,\]
\[C{{H}_{3}}C\equiv C-H+AgN{{O}_{3}}\xrightarrow[\Delta ]{N{{H}_{4}}OH}\]        \[\underset{\begin{smallmatrix} \text{Silver propynide (ppt}\text{.)} \\ \left( Mol.\,wt\text{ }=\text{ }147 \right) \end{smallmatrix}}{\mathop{C{{H}_{3}}-C\equiv C-Ag}}\,+N{{H}_{4}}N{{O}_{3}}+{{H}_{2}}O\]
\[\because \,182\,g\]   of tetrachloro alkane gives \[147\,g\]  of ppt.
\[\therefore \,36.4\,g\]   tetrachloro alkane gives \[\frac{147\times 36.4}{182}=29.4\,g\]     of precipitate

Triiodomethane (iodoform) has antiseptic property due to the liberation of free iodine and not due to iodoform itself.

$$\mathop {C{H_3}C{H_2}C{H_2}Cl}\limits_{{\text{Propyl chloride}}} + KCN \to $$      $$\mathop {C{H_3}C{H_2}C{H_2}CN}\limits_{{\text{ Butane nitrile}}} + KCl$$

$${C_2}{H_5}Br + KCN \to {C_2}{H_5}CN + KBr$$
Due to ionic nature, the attack by $$C{N^ - }$$ occurs through $$C$$ atom and alkyl cyanide is formed.

$$C{l_3}CCH{\left( {OH} \right)_2} + NaOH \to CHC{l_3} + HCOONa + {H_2}O$$

\[\begin{align} & C{{H}_{3}}C{{H}_{2}}C{{H}_{2}}Br\xrightarrow{aq.\,NaOH}C{{H}_{3}}C{{H}_{2}}C{{H}_{2}}OH\xrightarrow[\text{heat}]{A{{l}_{2}}{{O}_{3}}} \\ & C{{H}_{3}}CH=C{{H}_{2}}\xrightarrow{C{{l}_{2}}/{{H}_{2}}O}C{{H}_{3}}.CHOH.C{{H}_{2}}Cl \\ \end{align}\]

The presence of an electron withdrawing group $$\left( { - N{O_2}} \right)$$   at $$ortho$$  and $$para$$  - positions increases the reactivity of haloarenes.