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How can we say that if a charged nucleophile/base is present we can safely rule out the possibility that the reaction can take place via SN1/E1 mechanism? I have been trying to figure this out since hours. Help would be appreciated. Thank you. Source

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  • $\begingroup$ Could you please take a little more time to expand your question and add more details? It's pretty cryptic right now (at least for me). $\endgroup$ – Ari Ben Canaan Apr 15 '15 at 15:14
  • $\begingroup$ I have added all I could. To see from where my problem arose-check the link. $\endgroup$ – Karan Singh Apr 15 '15 at 15:15
  • $\begingroup$ It says so in rule 3: you cannot form a carbocation for obvious reasons. $\endgroup$ – Gerhard Apr 15 '15 at 21:21
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Strong nucleophiles tend to undergo SN1/E1 reactions whereas weak nucleophiles tend to undergo SN1/E1 reactions.

An increase in electron density will make a nucleophile stronger. This effect can be clearly seen when conjugate bases of common nucleophiles are stronger than the nuclephiles themselves. For example: $\ce{NH_2^- > NH_3} $.

In SN1/E1 reactions, the weak nucleophile can only attack the carbocation once the leaving group has left. This is precisely because it is a weak nucleophile.

IN SN2/E2 reactions, the strong nucleophile attacks the carbon before it can even form a carbocation. This forces the leaving group to leave. This is precisely because it is a strong nucleophile.

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