Test: Fundamental Concepts in Organic Reaction Mechanism (NCERT) - NEET MCQ

In C - Cl bond, the electron pair is carried away by Cl atom due to higher electronegativity.
C - Cl → C⁺ + Cl^-
Hence, carbon cation and chlorine anion are formed.

Electron deficient species act as electrophiles i.e., NO⁺₂.

NO₂⁺,AlCl₃,SO₃ and CH₃C⁺ = O are electrophiles.

Due to displacement of a-electrons towards more electronegative atom the bond becomes polar. The polar bond induces polarityto the adjacent bonds, this is inductive effect.

The order of +I effect of alkyl group is given as

Hydrogen does not exert I-effect. Its inductive effect is taken as zero. Electron releasing or electron withdrawing capability of other atoms are compared by hydrogen.

-NO₂ shows maximum electron with drawing or - I effect.

Fluorine is most electronegative atom and exerts maximum -I effect Hence F - CH₂COOH is the strongest acid.

(i) Br is more electronegative than H.
(ii) O is more electronegative than N.
(iii) O is more electronegative than S.
(iv) C1 is more electronegative than Br.

The strength of the acid increases with the inductive effect of the electronegative group attached to it (-I effect). The strength of the acid decreases with the presence of electron releasing group.

The resonating structures should have same number of electron pairs.

Phenoxide ion shows maximum resonating structures.

Hyperconjugation involves conjugation of a electrons of C - H bond and π electrons of multiple bond.
It is noticed due to delocalisation of σ- and π-bonds. It is . also known as no bond resonance.

shows 6 hyperconjuigatihg structures

For hyperconjugation α-carbon with respect to sp² hybridised carbon should have at least one hydrogen.

Tertiary carbocation is more stable than secondary and primary carbocatioris.

In carbocations, the carbon atom with positive charge has only 6 electrons in its valence shell.

Stability of alkyl carbocations can be explained by both inductive effect and hyperconjugation.

(CH₃)₃C⁺ is more stable than . Rest all are primary carbocations hence less stable.

Order of stability of carbanions is 1º > 2º > 3º;

Carbanions are stabilised by electron withdrawing groups. - NO₂ is stronger electron withdrawing group as compared to - CHO. At orthoposition, the effect is more pronounced.

Stability of carbanions decreases with increase in +l effect. + I effect is maximum in (CH₃)₃C^-, followed by (CH₃)₂CH^- and CH₃CH^-₂. In C₆H₅CH^-₂, resonance effect increases the stability. Hence, the order of stability is (iv) > (iii) > (ii) > (i).

Free radicals can undergo all given types of processes.

Free radical is formed as a result of homolytic fission hence it has an unpaired electron.

Radical is stabilized by α hydrogen. More the α-hydrogen more will be hyperconjugation more will be radical stabilization resonance. Resonance is also a good stabilizing factor and is given preference than hyperconjugation.

The electronegative atom in the carbon chain produces -I effect.