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Can I make N,N-dimethylaniline from aniline just by reacting it with $\ce{CH3X}$ ?

According to me, the lone pair of nitrogen in aniline is not nucleophilic enough (since it is in conjugation with the whole benzene ring) to be able to displace the $\ce{-X}$ group.

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  • $\begingroup$ Certainly pKb of hydrochloric acid (poorest leaving group among halides ) is 21 but pKb of aniline is 9.1, so aniline being a better base (and so better nucleophile, considering no other factors affect nucleophilicity comparison in this case) and so yes. $\endgroup$
    – Varun
    Commented Feb 19, 2016 at 7:22

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Yes this reaction will definitely work. Use a nice leaving group like iodide and the reaction should go easily. Although the nitrogen lone pair is delocalised into the benzene ring it is still quite nucleophilic. Additionally, the delocalisation is restored when the nitrogen loses a proton to get the substituted amine. As such there probably won't be a big problem with forming a quaternary ammonium salt (which is what usually happens if you try to alkylate amines) because doesn't have any opportunity to maintain delocalisation in the product and so will be disfavoured compared to the tertiary amine.

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    $\begingroup$ Hey bon, the lone pair from the N atom resonates to the carbon atoms in the ring, imparting the ortho/para carbons a negative charge. The negatively charged carbon atoms would be a better nucleophile than the neutral ntirogen atom. So, my doubt is that wouldn't the attack on iodomethane take place from those carbon atoms instead? (I am talking about a mechanism similar to what happens in Riemer Tienman reaction of phenols) Thanks! $\endgroup$ Commented Feb 22, 2018 at 15:36
  • $\begingroup$ @GaurangTandon The nitrogen has a far larger negative charge than the o/p carbons so that's not going to affect the reaction. Resonance is only a minor consideration here and it actually probably helps the reaction as I pointed out in my answer. $\endgroup$
    – bon
    Commented Feb 22, 2018 at 18:09

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