[Farbod]

I am in need of real help. My lecturer did not explain this to us properly and now I am so confused. I've been searching on the internet now for at least 3 hours and can't find what I am looking for Please help

The question is regarding nucleophilic aromatic substitution of pyridine. I need the full mechanisms showing why position 2 is favoured than position 3. All the thing I found so far either show an incomplete mechanism or show something completely different. Can someone help me please. If you could shoe me how it works, you will have saved me. We have been told this will come in the exam.

For example, this from wikipedia, does not show the reaction go to completion. What happens at the final stage?



Thanks

[hairygorillaz]

Nucleophile attacking at C2 or C4 put the negative charge on C3 or on N. Nucleophile attacking at C3 puts the negative charge at C2 or C4. So which one is more preferred (ie stable) ?

[Farbod]

Nucleophile attacking at C2 or C4 put the negative charge on C3 or on N. Nucleophile attacking at C3 puts the negative charge at C2 or C4. So which one is more preferred (ie stable) ?

I know negative charge is better on the N because it is better at delocalising the charge? So attack on 2,4 is more stable.
I just want something which can explain this is not too much detail. I just need to get the hang of it. My exam is in 2 days and I've been really trying but can't find anything which can explain. Just lecturer has not replied to email. Do you have any good sources please?

For example, I know charge on the N is more favoured but I don't understand why...

[zsinger]

Think electronegativity……;)
        Zack