Identify the target alcohol

The required product is 2-methylpropan-2-ol, whose structure is: $(CH_3)_3COH$

This is a tertiary alcohol.

Reaction of an ester with Grignard reagent

Ethyl ethanoate is: $CH_3COOC_2H_5$

Esters react with Grignard reagents in such a way that 2 moles of Grignard reagent are needed per mole of ester to finally give a tertiary alcohol.

General reaction: $RCOOR' + 2R''MgX \rightarrow R-C(OMgX)(R'')_2 \xrightarrow{H_3O^+} R-C(OH)(R'')_2$

Apply to the given case

Here:

• Ester: $CH_3COOC_2H_5$
• Grignard reagent: $CH_3MgBr$

First mole of $CH_3MgBr$ adds to the ester carbonyl, and after elimination of $C_2H_5O^-$, a ketone is formed: $CH_3COOC_2H_5 + CH_3MgBr \rightarrow CH_3COCH_3$ This ketone is propanone (acetone).

Then a second mole of $CH_3MgBr$ adds to propanone: $CH_3COCH_3 + CH_3MgBr \rightarrow (CH_3)_3COMgBr$

On hydrolysis: $(CH_3)_3COMgBr \xrightarrow{H_3O^+} (CH_3)_3COH$

Mole ratio

Thus, to form 1 mole of $2\text{-methylpropan-}2\text{-ol}$ from 1 mole of ethyl ethanoate, required moles of $CH_3MgBr$ are: $2$

Final integer answer

$\boxed{2}$

Comparison with stored answer

Stored correct answer = 2, which matches the derived result.