[apricimo]

Can someone tell me a good resource or explain nucleophilicty vs. basicity. I know usually a good nucleaphile is also a good base, but what are some ways for diferentiating when it is just a good nucleaphile or just a good base or both. How do Perodic trends, solvents, heat and other things play into all this. I know OH for example is a good nucleaphile also a good base in cold conditions I believe. Please help this is a topic that is discussed in classes, but I think is important when deciding between elimination or subsitution reactions. I would appreciate an e-mail too kumk0001@umn.edu

[Albert]

Have you already checked this out?

[apricimo]

No I did not see that site. Yeah that was more of what I was looking for; most sites give a Keq definition of a nucleophile and a base which is cmpletely useless in a qualitative analysis. I guess my next question is; what actually happens molecularly that make a base and a nucleophile? Is there a methodology in how one would be able to tell whether let's say Hydroxide (OH) is going to act as a nuclephole or as a base without knowing ahead of time a specific mechanism. Thoughts?

[Ψ×Ψ]

I don't think you can determine something like that beforehand.  Else, chemists would not suffer through so many failed reactions

[Yggdrasil]

I think to determine whether OH will act as a base or nucleophile, you have to look and see which acidic protons and electrophilic groups are available for it to react with.  If there many very acidic protons available (e.g. carboxylic acids), then it would likely act as a base.  If there are no acidic protons with pKa < ~10-11, but electrophilic groups, then it will likely act as a nucleophile.

[apricimo]

Yeah sure that makes sense. Thanks

[english]

Also, you have to think in terms of what a nucleophile actually is.  An electron-rich atom or compound/molecule.

All bases are Lewis bases, meaning they have at least one lone pair of electrons to bond with an acidic proton.  This satisfies the meaning of nucleophilicity.