# Why Grignard reagent don't react with alkylhalides ?

Mar 4, 2018

Because, assuming ordinary temperatures where substitution occurs, it'll just make more of itself again...

Grignard reagents are simply $R {:}^{-} {\text{MgX}}^{+}$, where $X = \text{Br}$ is the most optimal, but $X ' = \text{Cl}$ could be used. $R$ can simply denote alkyl groups.

If you seriously want to react with $R ' - \text{X} '$, you'll just get

$R {:}^{-} {\text{MgX"^(+) + R'-"X"' -> R-"X"' + R':^(-)"MgX}}^{+}$

via second order substitution, which is another Grignard reagent. So you don't get anywhere, really.