How can nitrogen be both acidic and basic in organic molecules?

[zmike]

I've been trying to brush up on my ochm but I haven't been able to find any solid/reliable rules on how to determine if a nitrogen is acidic or basic.
For eg. If a 5 carbon ring with nitrogen, it would be considered acidic but it has no protons.

I would really appreciate some help on clarifying this

Thank you

 

[sjb-2812]

At one level, they are both acidic and basic. What definitions of acid and base are you using?

 

[chemisttree]

I've been a chemist for a while now and this is the first time I've ever heard that nitrogen can be acidic in a 5-member ring if it has no protons. Ammonium can be acidic if it has at least 1 proton. So try this rule on for size:

"If a nitrogen atom bears a full positive charge and is bound to at least 1 proton, it's acidic."