This discussion is now closed.

Check out other Related discussions

Benzene & Phenol

emme786

Hey
Could anyone please explain to me why phenol is more reactive than benzene?
Thank you!

Reply 1

Eau

15

Benzene has a delocalised system - so not easily attacked by nucleophiles.

Phenol has a lone pair on the O, so can be easily hydrolysed.

Can someone confirm this?

Reply 2

driving_seat

http://www.chemguide.co.uk/organicprops/phenol/ring.html#top

Reply 3

pure_joy

9

Can someone confirm this?

I think you're right. the lone pair overlaps with the delocalised electrones, there's higher electron density, and the ring is more likely to react. phenol undergoes various types of reactions- electrophillic substitution, which involves the ring, and other reactions i.e. estrification - these involve the OH group.

Reply 4

username68316

3

Well basically, Phenol has the all important -OH part. This gives it acidic properties. It can donate the H+ ion to become C6H50-. This is because the ion is stable in the ionised state due to the delocalisation of the negative charge. This in turn gives rise to a whole host of other things.

Reply 5

Wangers

16

Phenol is more reactive then benzene - look up activating. it forms the ion because the ionised form is more stable then the phenol.

Reply 6

username68316

3

Wangers

Phenol is more reactive then benzene - look up activating. it forms the ion because the ionised form is more stable then the phenol.

Not it's not. In solution, there is a greater concentration of phenol than phenoxide ions (in any reasonable solution). If what you're saying is true then it would be the other way around. Phenol is more likely to ionise than benzene, but that in no way suggests that the phenoxide is more stable than the phenol.

Reply 7

=gabriel=

13

Nathan Ley3

Not it's not. In solution, there is a greater concentration of phenol than phenoxide ions (in any reasonable solution). If what you're saying is true then it would be the other way around. Phenol is more likely to ionise than benzene, but that in no way suggests that the phenoxide is more stable than the phenol.

Indeed, it has a pKa of about 10 so you need a base to deprotonate it to a greater extent (such as NaOH to make sodium phenoxide). It is more reactive because the hydroxyl donates electrons to the benzene ring by conjugation (conjugation of the oxygen lone pair) which makes the aromatic system more nucleophilic and therefore more susceptible to electrophiles. This is called the 'enol nature of phenol' whiche means it behaves a bit like the pi system of enols.
Phenoxide is of course even more reactive than phenol towards electrophiles but in many reactions there is no need for a base or it would even spoil the experiment.
So it is the nature of the -OH group and its interactions with the aromatic system that make phenol more reactive, not the acidity of the group!

Reply 8

Wangers

16

oops looks like ive buggered up my notes somewhere - thanks people

Reply 9

RyanY

1

The oxygen is electronegative and so has a negative inductive effect reducing electron density at position 1 to which the o-h grp is attached. This in turn sets up dipoles so that 1,3,5- slightly positive, 2,4,6 - slightly negative.
Thus positions 2,4,6 on the benzene ring are more susceptible to electrophilic attack, something that benzene does not exhibit at these positions due to the delocalisation and no regions where there's enhanced electron density.

Benzene & Phenol

Related discussions

Latest

Trending

Trending

Articles for you