Adding an acid replaces the $\ce{-MgBr+}$ with an $\ce{H+}$. Why does this happen? Is $\ce{H+}$ a better electrophile than $\ce{MgBr+}$?
Or, to put it another way, why doesn't $\ce{MgBr}$ stays attached to $\ce{O}$?
$\begingroup$
$\endgroup$
-
$\begingroup$ Well, it's symbolic scheme of reaction not telling what exactly Mg(OH)Br in H2O/t-butanol solution "looks like". t-butanolate isn't monomer and hydroxide is solvated, but those are kinda details. $\endgroup$ – Mithoron Jul 24 '17 at 20:34
-
$\begingroup$ Isn't that a Grignard reagent? If so, it's a strong base and a nucleophile, isn't it? Making the intermediate carbocation less stable, more reactive with acidic hydrogens? $\endgroup$ – bonCodigo Jul 28 '17 at 5:43
$\begingroup$
$\endgroup$
We are taking about electrophilicity of ions.
It basically depends upon:
1. charge on the ion(+)
2. density of plus charge on it
So comparing $\ce{H+}$ and $\ce{CH3+}$, the former has a higher plus charge density so that's why it will be more attracted towards 'O'.
