Question

Write the reaction equations of (i)2-bromo-2-methylpropane + magnesium in dry ether; (ii)product of (i) + water?

Answer 1

This is the preparation and hydrolysis of a Grignard reagent.

Explanation:

Part (i)

This is the preparation of a Grignard reagent.

`"R-X" + "Mg" stackrelcolor (blue)("dry ether")(→) underbrace("R-MgX")_("Grignard Reagent")`

Your equation is

`("CH"_3)_3"C-Br" + "Mg" stackrelcolor (blue)("dry ether")(→) ("CH"_3)_3"C-MgBr"`

Part (ii)

This is the hydrolysis of a Grignard reagent.

`"R-MgX" + "H"_2"O" → "RH" + "MgX(OH)"`

The `"R-MgX"` behaves as if it were `"R"^- ,""^+"MgX"`.

The `"R"^-` is a strong base, so it removes a proton from the water to form `"RH"`.

Your equation is

`"(CH"_3)_3"C-MgBr" + "H"_2"O" → "(CH"_3)_3"C-H" + "MgBr(OH)"`

Note: the `"MgBr(OH)"` is a gelatinous substance, so the hydrolysis is usually carried out in the presence of dilute acid to dissolve the basic salt.