[cupid.callin]

Hi all,

Can anyone help me with the with the Basicity of purine...

Structure given.

According to Huckel's Rule ... For aromaticity the molicule should be planar.
so in this structure, N3 is sp3 hybrid so no aromaticity but all are sp2 hecnce they donate their elec. in resonance. but N4 is also not taking part in aromaticity (in its ring but takes part in other.)
So N3 should be basic.

BUT I AM NOT SURE.

Please help me.

[orgstudy]

I guess you are right

[Hybrid]

no search for theophylline and u will know that NH of imidazole ring is acidic not basic at all >>> forms many salts "amines, na , k ,...etc"

[cupid.callin]

I dont understand why they are acidic.

And yo want to say purine is not basic?

[Hybrid]

no purines are amphoteric compound possess both acidic and basic group, there is a good book for discussing every ring with all its electronic characters and major reaction "Katritzky  Comprehensive Heterocyclic Chemistry." try to search for it

really very helpful book especially in the  electronic characters .

[cupid.callin]

I cant find the link for the book. Can you send me the link?

[Hybrid]

ok
1. link for Katritzky  vol 5 , contain purines

http://www.alldownloadlinks.com/comprehensive-heterocyclic-chemistry-volume-5-by-alan-r-katritzky_1_4146151284027284.html

2.also there is another good reference  Chemistry of Heterocyclic Compounds, Volume 54

http://ifile.it/de6l294/54.rar

3. also volume 24 II of the latter series but i have no link 4 it right now

[cupid.callin]

Thanks for your book. I got my answer