Chemistry Class-11: Chapter –12. The Organic Chemistry Some Basic Principles and Techniques Part – 7

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Question: 42

Draw the resonance structures of the following compounds;

(i)

Resonance

Resonance

(ii)

(iii)

Answer:

(i)

The resonance structures

Mechanism

(ii)

The resonance structures

Mechanism

(iii)

The resonance structures

Mechanism

Question: 43

Identify the most stable species in the following set of ions giving reasons:

(i)

(ii)

Answer:

(i) The replacement of hydrogen by bromine increases positive charge on carbon atom and destabilises the species.

(ii) is most stable because electronegativity of chlorine is more than hydrogen. On replacing hydrogen by chlorine, negative charge on carbon is reduced and species is stabilised.

Question: 44

Give three points of differences between inductive effect and resonance effect.

Answer:

Differences between Inductive Effect and Resonance Effect
Differences between inductive effect and resonance effect

Inductive effect

Resonance effect

(i)

Use σ-electrons

(a)

Use electrons or lone pair of electrons

(ii)

Move up to 3-carbon atoms

(b)

All along the length of conjugated system

(iii)

Slightly displaced electrons

(c)

Complete transfer of electrons

Question: 45

Which of the following compounds will not exist as resonance hybrid. Give reason for your answer:

(i)

(ii)

(iii)

Answer:

; Any possible contributing structure will have charge separation and incomplete octet of electrons on atoms. So the structure will be unstable due to high energy. e.g.,

Question: 46

Why does act as an electrophile?

Answer:

Oxygen attached to sulphur

Electrophile

Three highly electronegative oxygen atoms are attached to sulphur atom. It makes sulphur atom electron deficient. Due to resonance also, sulphur acquires positive charge. Both these factors make an electrophile.

Question: 47

Resonance structures of propenal are given below. Which of these resonating structures is more stable? Give reason for your answer.

Answer:

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