(a)

(b)
\(\underset { (isopropyl\quad alcohol) }{ { CH }_{ 3 }COOH } \overset { { H }^{ + }/{ K }_{ 2 }{ Cr }_{ 2 }{ O }_{ 7 } }{ \longrightarrow } { CH }_{ 3 }-\underset { \overset { || }{ O } }{ C } -{ CH }_{ 3 }\overset { (O) }{ \longrightarrow } \underset { (Acentic\quad acid) }{ { CH }_{ 3 }COOH } \)

(i) C₂H₄ is CH₂=CH₂ is a simple alkene. A is ethylene.
(ii) Ethylene (A) reacts with dil H₂SO4 to give ethanol (B)
\(\underset { Ethylene\\ \quad \quad \quad (A) }{ { CH }_{ 2 }{ CH }_{ 2 } } \overset { dil{ H }_{ 2 }{ SO }_{ 4 } }{ \longrightarrow } \underset { ethanol\\ \quad \quad (B) }{ { CH }_{ 3 }-{ CH }_{ 2 }-OH } \) 
(iii) Ethylene (A) reacts with Cl₂ to give 1,2 dichloro ethane (C)
\(\underset { (Ethylene)\\ \quad \quad \quad (A) }{ { CH }_{ 2 }={ CH }_{ 2 } } \overset { { cl }_{ 2 } }{ \longrightarrow } \underset { (1,2-dicholoro\quad ethene) }{ \underset { \overset { | }{ Cl } }{ { CH }_{ 2 } } -\underset { \overset { | }{ Cl } }{ { CH }_{ 2 } } } \) 

(i) C₂H₆0 is CH₃-CH₂-OH which is a primary alcohol (A)
(ii) CH₃-CH₂-OH (A) reacts with H⁺/K₂Cr₂O₇ to give acetaldehyde (B)
\(\underset { Acetaldhyde\\ (B) }{ { CH }_{ 3 }CHO } \overset { (o) }{ \longrightarrow } \underset { Acetic\quad acid\\ (c) }{ { CH }_{ 3 }COOH } \) 
(iii) CH₃CHO (B) which on further oxidation to give acetic acid (C).
\(\underset { Acetic\quad acid\\ (c) }{ { CH }_{ 3 }COOH } \overset { (O) }{ \longrightarrow } \underset { Acetyl\quad chloride\\ (D) }{ { CH }_{ 3 }COCl+{ SO }_{ 2 }+HCl } \)

(a)

(b)

(c)

(d)

Substitution reactions are classified into three types. They are,
(i) Nucleophilic substitution reaction.
(ii) Electrophilic substitution reaction.
(iii) Free radical substitution reaction.
(i) Nucleophilic substitution reaction: A nucleophilic substitution reaction in organic chemistry is a type of reaction where a nucleophilic gets attached to the positive charged atoms or molecules of the other substance. A good example of a nucleophilic substitution reaction is the hydrolysis of alkyl bromide, under the basic conditions where in the nucleophile is nothing but the base \(\overset { \ominus }{ O } H\), whereas the leaving group is the Br^Ө. The reaction for the following is as give below.
\(\underset { (mentyl\quad bromide) }{ { CH }_{ 3 }Br } \overset { aq.\overset { \ominus }{ O } H }{ \longrightarrow } \underset { (methanol) }{ { CH }_{ 3 }OH } +{ Br }^{ \ominus }\) 

(ii) Electrophilic substitution reaction: The electrophilic substitution reaction involves the electrophiles. The electrophilic reactions occur mostly with the aromatic compounds. This types of substitution reaction are basically defined as those chemical reactions where the electrophile replaces the functional group in a compound but not the hydrogen atom, sometimes hydrogen atom can be also replaced by electrophiles. For example:

(iii) Free radical substitution reaction: Free radical substitution reaction involving free radicals are a reactive intermediate
\(A-X+\overset { \bullet }{ Y } \longrightarrow A-Y+\overset { \bullet }{ X } \) 
\({ CH }_{ 4 }+\overset { \bullet }{ C } l\longrightarrow \overset { \bullet }{ C } { H }_{ 3 }+HCl\) 
\(\overset { \bullet }{ C } { H }_{ 3 }+\overset { \bullet }{ C } l\longrightarrow { CH }_{ 3 }Cl\)