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

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Answer 1 · 2015-08-27T00:17:20

This is the preparation and hydrolysis of a Grignard reagent.

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.