This reacts with aldehydes and ketones to form additive products, which are decomposed on treatment with water, yielding secondary and tertiary alcohols respectively. Thus with acetaldehyde: -

And on decomposing with water: -

In practice, acidified water is used: this dissolves the magnesium hydroxide produced.

Similarly, by using methyl magnesium iodide and acetone we can obtain the tertiary butyl alcohol, trimethyl carbinol: -

And with water: -

In an analogous manner, esters react with two molecules of the magnesium alkyl halide to form, in general, tertiary alcohols. Formic acid esters, however, yield secondary alcohols.