Reaction Intermediates

IMPORTANT

Reaction Intermediates: Overview

This topic covers concepts, such as, Reaction Intermediates, Carbanions, Carbene & Benzyne etc.

Important Questions on Reaction Intermediates

HARD
IMPORTANT

Correct order of rate hydrolysis or rate of reaction towards AgNO3 for following compounds is: 

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MEDIUM
IMPORTANT

Which one of the following carbonyl compound when treated with dilute acid forms the more stable carbocation?

MEDIUM
IMPORTANT

The abstraction of proton will be fastest from which carbon in the following compound?

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EASY
IMPORTANT

Write correct order of stability of following carbocations :

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EASY
IMPORTANT

Rank the following free radicals in order of decreasing stability:

I C 6 H 5 C HC 6 H 5

I I C 6 H 5 - C H - C H = C H 2

I I I C H 3 - C H - C H 3

I V C 6 H 5 - C H - C H 3

VCH3CH2CH2CH2CH2

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MEDIUM
IMPORTANT

The correct stability order for the following species is

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MEDIUM
IMPORTANT

An organic reaction occurs through making and breaking of bonds. The breaking of bonds may occur either homolytically leading to the formation of radicals or heterolytically generating positively and negatively charged species. The neutral species (free radicals, carbenes, nitrenes, etc.) and positively charged species being electron deficient are collectively called electrophiles while neutral and negatively charged species which are electron rich are called nucleophiles. An organic reaction usually involves the attack of a reagent (radicals, positively and negatively charged species) on the substrate molecule). The substrate molecule, although as a whole electrically neutral, has centers of low and high electron density due to displacement of bonding electrons. These electron displacements occur through inductive, electromeric, resonance and hyperconjugation effects. Whereas inductive effects involve displacement σ-electrons, resonance effects involve transfer of n- and π-electrons along a conjugated system. Hyperconjugatlon effects, on the other hand, involve σ-π-conjugation. Both inductive and hyperconjugation effects can be used to explain the stability of carbocations and free radicals which follow the stabilIty order : 3°>2°>1°. The stability of carbanions, however, follows opposite order.
The stability of a molecule can be judged on the basis of contribution of its resonance structures. Resonance structures have same position of nuclei and have the same number of unpaired electrons. Among resonance structures, the one which has greater number of covalent bonds, has less separation of opposite charges, a negative charge on more electronegative and a positive charge on a more electropositive atom are more stable than others.

The geometry of a carbocation is _____.

MEDIUM
IMPORTANT

Triplet state of Reaction intermediates like carbene & nitrene are more stable than their singlet state. This fact can be explained on the basis of 

MEDIUM
IMPORTANT

The stability of carbanions

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follows the order

MEDIUM
IMPORTANT

Which of the following is a suitable condition for homolytic bond fission?

EASY
IMPORTANT

Which of the following compounds has planar geometry?

EASY
IMPORTANT

What is the geometry of methyl free radical?

EASY
IMPORTANT

Which is the least stable free radical?

EASY
IMPORTANT

Which is the most stable free radical?

EASY
IMPORTANT

_____ are formed by the homolytic cleavage of a covalent bond.

EASY
IMPORTANT

The stability of the free radicals due to inductive effect follows the order,

EASY
IMPORTANT

Explain the stability of free radicals due to inductive effect.

EASY
IMPORTANT

The correct order of increasing stabilities of the following carbocations.

(i) Allyl carbocation
(ii) Ethyl carbocation
(iii) Benzyl carbocation
(iv) Isobutyl carbocation

EASY
IMPORTANT

Explain the factors that affect the stability of the carbanion.

EASY
IMPORTANT

State the hybridisation of carbanion.