(i) In triphenylmethyl cation, due to resonance the positive charge can move at both the o- and p-positions of each benzene ring.

[Six more structures are possible due to resonance in other two benzene rings]
(ii) Totally nine resonance structures are possible for 3 benzene rings
(iii) ∴ Triphenylmethyl cation is highly stable due to these nine resonance structure.

(i) 2-methyl butane has four different sets of equivalent H-atoms.
(ii) Removal of H-atom from any of C-atom gives four different carbocations.
(i) \(C{ H }_{ 3 }\rightarrow \overset { \beta }{ \underset { \overset { | }{ C{ H }_{ 3 } } }{ CH } } \rightarrow \overset { \alpha }{ C{ H }_{ 2 } } \rightarrow \overset { + }{ C{ H }_{ 2 } } \)
(ii) \(C{ H }_{ 3 }\rightarrow \underset { \overset { | }{ C{ H }_{ 3 } } }{ CH } -\overset { + }{ C{ H } } \leftarrow C{ H }_{ 3 }\)
(iii) \(C{ H }_{ 3 }\rightarrow \overset { + }{ \underset { \overset { | }{ C{ H }_{ 3 } } }{ C } } \leftarrow C{ H }_{ 2 }-C{ H }_{ 3 }\)
(iv) \(\overset { + }{ C{ H }_{ 2 } } \leftarrow \underset { \overset { | }{ C{ H }_{ 3 } } }{ CH } \leftarrow C{ H }_{ 2 }-C{ H }_{ 3 }\)
(iii) Stability order of carbocation is 3⁰ > 2⁰ > 1⁰
(iv) Though I & IV are primary carbocations, I has (α-CH₃ group at β-carbon and while IV has -CH₃ at α-carbon.
(v) +I effect decreases with distance, hence IV is more stable than I
(vi) ∴ The overall stability is I < IV < II < III

(i) C-Br is more polar than C-H (due to electronegativity )
(ii) C-O is more polar than C-N
(iii) C-O is more polar than C-S

(i) CH₃ - OH : Does not exist as resonance hybrid due to absence of π-electrons.
(ii) R-CO NH₂ : Can exist as resonance hybrid due to the presence of non-bonding electrons on N and n-electrons on C = O bond.

(iii) CH₃-CH = CH-CH₂NH₂: Does not exist as resonance hybrid, because the lone pair on N-atom is not conjugated with n-electrons of the double bond

(i) Brominatin of alkene to give bromo alkane.

(iii) In this reaction, benzoyl peroxide acts as a radical initiator. The mechanism involves free radicals.
\({ H }_{ 2 }C=CH+H-Br\overset { \overset { Benzoyl }{ Peroxide } }{ \longrightarrow } C{ H }_{ 3 }-C{ H }_{ 2 }-Br\)

In this reaction an atom or a group of atoms attached to a carbon atom is replaced by a new atom or a group of atoms. Based on the nature of the attacking reagent, this reactions can be classied as
i) Nucleophilic substitution
ii) Electrophilic substitution
iii) Free radical substitution
(i) Nucleophilic substitution:
This reaction can be represented as

Here Y- is the incoming nucleophile or and attacking species and x- is the leaving group.
Example: Hydrolysis of alkyl halides
\(C{ H }_{ 3 }\overset { aqueous\quad OH }{ \longrightarrow } C{ H }_{ 3 }OH+Br\)
Aliphatic nucleophilic substitution reactions take places either by S_N1 or S_N2 mechanism.
(ii) Electrophilic substitution:

Here Y+ is an electrophile
Example: Nitration of Benzene

(iii) Free radical substitution:
\(A-X+{ Y }^{ . }\longrightarrow A-Y+\overset { . }{ X } \)
\(C{ H }_{ 4 }+\overset { . }{ C } l\longrightarrow \overset { . }{ C } { H }_{ 3 }+HCl\)
Aliphatic electrophilic substitution
A general aliphatic electrophilic substitution is represented as
\(R-X+{ E }^{ \oplus }\longrightarrow R-E+{ X }^{ \oplus }\)
\({ R }_{ 2 }NH+N\overset { + }{ O } \longrightarrow { R }_{ 2 }N-NO+{ H }^{ + }\)

The inductive effect represents the ability of a particular atom or a group to either withdraw or donate electron density to the attached carbon. Based on this ability the substituents are classied as +I groups and -I groups. Their ability to release or withdraw the electron through sigma covalent bond is called +I effect and -I effect respectively.
Higher the electronegativity of the substitutent, greater is the -I effect. The order of the -I effect of some groups are given below.
NH₃⁺ > NO₂ > CN > SO₃H > CHO
Highly electropositive atoms and atoms are groups which carry a negative charge are electron donating or +I groups.
Example: Alkali metals, alkyl groups such as methyl, ethyl, negatively charged groups such as CH₃O^-, C₂H₅O^-, COO^- etc
Lesser the electronegativity of the elements, greater is the +I effect. The relative order of +I effect of some alkyl groups is given below
-C(CH₃)₃> - CH(CH₃)₂ > - CH₂CH₃ > - CH₃

(i) The arrangement of atoms must be identical or almost same in every resonance structure.
(ii) The energy content of all the canomical forms must be almost same.
(iii) Each canocial form must have the same number of unpaired electrons.

There are three types of electron movement viz.,
1. lone pair becomes a bonding pair.
2. bonding pair becomes a lone pair
3. a bond breaks and becomes another bond
Type 1: A lone pair to a bonding pair

Type 2: A bonding pair to a lone pair

Type 3: A bonding pair to an another bonding pair