Why Is Para Nitro Phenol More Acidic Than Ortho Nitro Phenol?

[harini07]

Homework Statement

In

is more acidic than

but In

(para nitro phenol) is more acidic than

(ortho nitro phenol) why?

Homework Equations

in ortho nitro benzoic acid due to -I and -M effect it is more acidic than it's para species (-I effect more in ortho position) .

The Attempt at a Solution

In the latter compounds, due to intra molecular H-bonding, para compound is more acidic than that of the ortho compound. my doubt is in ortho nitro benzoic acid, isn't there any intra molecular H-bonding cause a carboxylic acid can form H-bonding so does the nitro compound. please solve my query :/[/B]

 

[Ygggdrasil]

For o-nitro benzoic acid and o-nitro phenol, try drawing out all the bonds (including N-O and O-H bonds) to see what the intramolecular hydrogen bonding looks like. You may see a problem with o-nitrobenzoic acid but not o-nitro phenol.

 

[harini07]

For o-nitro benzoic acid and o-nitro phenol, try drawing out all the bonds (including N-O and O-H bonds) to see what the intramolecular hydrogen bonding looks like. You may see a problem with o-nitrobenzoic acid but not o-nitro phenol.

sorry i don't understand..please explain further :/

 

[Borek]

Have you tried to draw what Ygg suggested?

 

[harini07]

Have you tried to draw what Ygg suggested?

ok..this ortho nitro benzoic acid. there is this unwanted -ve sign here.

where as here in ortho nitro phenol, it could easily form intramolecular H-bonding...sorry! still, i didnt get the point! do explain me! it would be of great help :)

 

[Ygggdrasil]

For the nitro benzoic acid, draw the O-H bond. Also, keep in mind the preferred angles for each bond. You should see the problem.

If you're still not getting it, try building a model of you have a model kit.