At what position does an electrophilic substitution reaction takes place in furan?

Pyrrole, thiophene, and furan gives electrophilic aromatic substitution reaction. These compounds are more reactive compared to benzene. Electrophiles majorly attack on 2nd position rather than 3rd position in these heterocyclic compounds.

Why electrophilic substitution in pyrrole occurs at C2 and not at C3?

The difference is fairly clear: electrophilic aromatic substitution (EAS) occurring at carbon-2 gives one more resonance structure than on carbon-3, so that intermediate is more stable. Thus, EAS more readily occurs on carbon-2 starting with pure pyrrole.

At which position of pyrrole electrophilic substitution reaction is most preferred?

Whereas attack at the β-position produces an intermediate that can be described by only 2 resonance structures. Therefore, the intermediate formed by α attack is more stable and the activation energy leading to it will be reduced. Consequently, electrophilic attack at the α position in pyrrole is preferred.

Why is furan less reactive than pyrrole towards electrophilic substitution reaction?

The lower reactivity of furan than pyrrole is because the oxygen atom accommodates positive charge less readily than the nitrogen atom, while the higher reactivity of furan than thiophene can be attributed to the smaller orientation effect (+M effect) of sulfur than that of oxygen.

Why does electrophilic substitution in pyridine take place at position 3?

Electrophilic substitutions Substitutions usually occur at the 3-position, which is the most electron-rich carbon atom in the ring and is, therefore, more susceptible to an electrophilic addition.

What happens when pyrrole undergoes electrophilic substitution reaction?

When electrophilic substitution takes place at 2nd position of pyrrole, it will lead to the formation of three resonating structures. When electrophilic substitution takes place at the 3rd position of pyrrole, it will lead to the formation of two resonating structures only.

What are the conditions for electrophilic substitution?

In an electrophilic substitution reaction, a pair of π-bonded electrons first attacks an electrophile – usually a carbocation species – and a proton is then abstracted from an adjacent carbon to reestablish the double bond, either in the original position or with isomerization.

Why does electrophilic substitution reactions of quinoline takes place at benzene ring rather than pyridine ring?

Are less reactive toward electrophilic substitution than benzene because of the nitrogen atom that withdraws electrons from the ring. iii. Electrophilic substitution occurs on the benzene ring rather than on the nitrogen-containing pyridine ring and a mixture of substitution products is obtained.

Why does pyridine react under vigorous conditions with electrophilic reagents?

Explanation: When electrophilic substitution reaction of pyridine is carried out in acidic conditions then pyridine ring will further get deactivated forming pyridinium ion. However, under more vigorous conditions the usual electrophilic substitution reaction can be possible but yield will be less. 2.

Why is pyrrole more reactive for electrophilic substitution than furan?

Thus pyrrole is more reactive for electrophilic substitution at C-2 and C-5 postions. The same chemistry will happen with furan. This is because Nitrogen and Oxygen are Most electronegative elements after fluorine and hence they create maximum electron deficiency on adjacent carbon atoms .

Why does subsitution occur at position 2 for furan?

Position 2 is equivalent to 5 and position 3 is equivalent to 4. Here, we have only 2 resonance forms. Here are 3 resonance forms. The stability of a structure is usually higher when there are more resonance forms. Hence, subsitution will occur at position 2 for furan. 8 clever moves when you have $1,000 in the bank.

Where does the attack of electrophiles take place in pyrrole?

That’s why the attack of electrophiles takes place at 2 nd position in pyrrole, thiophene, and furan.

What happens in the second step of electrophilic substitution?

In the faster second step of the electrophilic substitution mechanism, the proton bound to the sp 3 -hybridized ring carbon atom leaves, restoring the aromatic π system. A nucleophile, acting as a base, extracts the leaving proton.