(i) l-butanol
(ii) I-chlorobutane
(iii) but-l-ene
(i) \(\underset { 1-buanol }{ CH_{ 3 }{ CH }_{ 2 }{ CH }_{ 2 }Cl } \overset { P/{ I }_{ 2 } }{ \longrightarrow } \underset { 1-Iodobutene }{ { CH }_{ 3 }{ CH }_{ 2 }{ CH }_{ 2 }I } \) 
(ii) \({ CH }_{ 3 }{ CH }_{ 2 }{ CH }_{ 2 }Cl+Nal\overset { Acetone }{ \longrightarrow } { CH }_{ 3 }{ CH }_{ 2 }{ CH }_{ 2 }I+Nacl\) 
(iii) 

(i) Addition of Cl₂ to Ethylene
\(\underset { Ethylene }{ { CH }_{ 2 }={ CH }_{ 2 }+{ Cl }_{ 2 } } \longrightarrow \underset { Ethylene\quad dichloride }{ \underset { \overset { | }{ Cl } }{ C } { H }_{ 2 }-\underset { \overset { | }{ Cl } }{ C } { H }_{ 2 } } \)
(ii) Action of PCl, on Ethylene glycol
\(\underset { Ethylene\quad glucol }{ \underset { \overset { | }{ OH } }{ C } { H }_{ 2 }-\underset { \overset { | }{ OH } }{ C } { H }_{ 2 } } +2P{ { Cl }_{ 5 } }\longrightarrow \underset { Ethylene\quad dichloride }{ \underset { \overset { | }{ Cl } }{ C } { H }_{ 2 }-\underset { \overset { | }{ Cl } }{ C } { H }_{ 2 } } +2POCl_{ 3 }2HCL\)

(i) Carbon compounds containing more than one halogen atom are called polyhalogen compounds.
(ii) They are classified as
(i) gem dihalides
(ii) Vicinal dihalides.
(a) Gem dihalide: In this compound, two halogen atoms are attached to one carbon atom
e.g, CH₃CHCl₂ ethylidene chloride.
(b) Vicinal dihalide: In this compound, two halogen atoms are attached to two adjacent carbon atoms.
\(\underset { \overset { | }{ Cl } }{ { CH }_{ 2 }- } \underset { \overset { | }{ Cl } }{ { CH }_{ 2 } } \) 1, 2-dichloro ethane

Solid carbon dioxide reacts with grignard reagent to form addition product which on hydrolysis yields acetic acid.

(i) Hydrolysis :
\(\underset { \overset { | }{ Cl } }{ { CH }_{ 2 } } -\underset { \overset { | }{ Cl } }{ { CH }_{ 2 } } \overset { 2KOH }{ \underset { (aq) }{ \longrightarrow } } \quad \underset { \overset { | }{ OH } }{ { CH }_{ 2 } } -\underset { \overset { | }{ OH } }{ { CH }_{ 2 } } +2KCl\)
Ethylene dichloride              Ethylene glycol
(ii) Dehalogenation :
\(\underset { \overset { | }{ Cl } }{ { CH }_{ 2 } } -\underset { \overset { | }{ Cl } }{ { CH }_{ 2 } } +Zn\overset { Methanol }{ \underset { \triangle }{ \longrightarrow } } \quad { CH }_{ 2 }=\underset { Ethylene }{ CH_{ 2 } } +ZnC{ l }_{ 2 }\)
Ethylene dichloride
(iii) Dehydrohalognenation :
\(H-\overset { \underset { | }{ Cl } }{ \underset { \overset { | }{ H } }{ C } } -\overset { \underset { | }{ H } }{ \underset { \overset { | }{ Cl } }{ C } } -H+2KOH\overset { Ethanol }{ \underset { \triangle }{ \longrightarrow } } \)
Ethylene dichloride
\(\underset { Acetylene }{ HC } \equiv CH+2KCl+{ H }_{ 2 }\)

When a solution of haloalkane in either is treated with magnesium, we will get alkyl magnesium halide known as Grignard reagent, ethyl magnesium bromide is prepared from ethyl bromide as:
\(\underset { Ethyl \ bromide }{ { CH }_{ 3 }-{ CH }_{ 2 }Br+ } \)Mg \(\underrightarrow { dry \ ether } \)\(\underset { Ethyl \ magnesium \ bromide\\ (or)\\ Grignard \ reagent }{ { CH }_{ 3 }{ CH }_{ 2 }{ MgBr } } \)

Silver salt of fatty acids (CH₃CH₂COOAg), e.g., silver propionate treated with Br₂/CCI₄ gives bromoalkane. This reaction is called Hunsdicker reaction
CH₃ - CH₂COOAg + Br₂ \(\xrightarrow [ { reflux }] { CCl_{ 4 } }\) CH3 - CH₂Br + CO_{2 ↑} + AgBr

Chloro (or) bromoalkanes on heating with AgF give fluoroalkanes. This reaction is called Swarts reaction.
\(\underset { Ethanol }{ { CH }_{ 3 } } -{ CH }_{ 2 }+Br+AgF\underrightarrow { \triangle } \underset { Fluoroethane }{ { CH }_{ 3 }-{ CH }_{ 2 }F } +AgB\)

Reactions of arenes with iodine is reversible in nature. So aryl iodides are prepared in the presence of an oxideising agent such as HNO₃, HIO₄, etc., inorder to oxidise the HI formed during iodination.

(i) Ⓐ of molecular formula CH₂O is identified as HCHO, formaldehyde.
(ii) Formaldehyde reacts with CH₃MgI followed by hydrolysis to give ethanol, CH₃- CH₂OH B as the product.

(iii) Ethanol Ⓑ, reacts with PCl₅ to give C₂H₅CI, Ethyl chloride © as the product.

(iv) CH₃-CH₂CI © on reaction with alcoholic KOH undergoes dehydrohalogenation to give ethylene CH₂ = CH₂ © as the product.
\(CH_{ 3 }-{ CH }_{ 2 }Cl\overset { alcoholic }{ \underset { KOH }{ \longrightarrow } } \underset { Ethlene }{ { CH }_{ 2 }={ CH }_{ 2 }+HCl } \)

(i) The aromatic hydrocarbon Ⓐ is Benzene, C₆H₆.
(ii) Benzene reacts. with Cl₂ to give chlorobenzene (C₆H₅CI), as Ⓑ as the product.

(iii) Chlorobenzene Ⓑ acts with sodium hydroxide to give (C₆HsOH) phenol, © as the product.

(iv) Chlorobenzene reacts with ammonia to give Aniline, C₆H₅NH₂Ⓓ as the product.

(i) Ethyl methyl ether: Lower halogenated ether reacts with grignard reagent to form higher ether.
\(\underset { Chloro\quad dim\quad ether }{ { CH }_{ 3 }O-{ CH }_{ 2 }Cl } +\underset { Methyl\quad magnesium\\ iodide }{ { CH }_{ 3 }Mgl } \longrightarrow \underset { Ethyl\quad methyl\quad ether }{ { CH }_{ 3 }-O-{ CH }_{ 2 }-{ CH }_{ 3 } } \) 
(ii) Methyl cyanide: Grignard reagent reacts with cyanogen chloride to form alkyl cyanide.

(iii) Methane: Grignard reagent reacts with water to give methane as product.

Reaction between iso-butylene and HCI are as follows:

(ii) When CH₃- Br is treated with KCN, methyl cyanide is formed.
\(\underset { Methyl\\ Bromide }{ { CH }_{ 3 } } -Br+\underset { Potcyanide }{ KCN } \longrightarrow \underset { Methyl\\ Cyanide }{ { CH }_{ 3 } } -CN+\underset { Pot\\ Bromide }{ KBr } \)
(iii)  is a chiral molecule, as four atoms attached to *C - atom are different
(iv) 
This order is due to steric reasons, the order of reactivity in S_N2 follows the order: 1°>2°> s 3°.