Answer :
To prepare ethyl alcohol (ethanol, C[tex]_2[/tex]H[tex]_5[/tex]OH) using a Grignard reagent, a chemical reaction involving a Grignard reagent and an appropriate carbonyl compound is utilized. Grignard reagents are organomagnesium compounds and have the general formula RMgX, where R is an alkyl or aryl group and X is a halogen (usually chlorine, bromine, or iodine).
To obtain ethyl alcohol specifically, the Grignard reagent must react with formaldehyde (HCHO). Here’s a step-by-step explanation of the reaction process:
Grignard Reagent Preparation: Typically, the Grignard reagent used would be methylmagnesium iodide (CH[tex]_3[/tex]MgI). This can be prepared by reacting methyl iodide (CH[tex]_3[/tex]I) with magnesium (Mg) in an anhydrous diethyl ether solution.
Reaction with Formaldehyde: The Grignard reagent (CH[tex]_3[/tex]MgI) is then reacted with formaldehyde (HCHO) in an ether solution. The addition of the Grignard reagent to the carbonyl group in formaldehyde forms an intermediate alcoholate complex.
Hydrolysis: This intermediate is then hydrolyzed, usually by adding a dilute acid like hydrochloric acid (HCl) or water, to yield ethyl alcohol. The reaction sequence can be summarized as follows:
[tex]\text{CH}_3\text{MgI} + \text{HCHO} \xrightarrow{\text{ether}} \text{(CH}_3\text{CH}_2\text{OMgI)} \xrightarrow{\text{H}_2\text{O}} \text{CH}_3\text{CH}_2\text{OH} + \text{MgI}\_ ext{2}[/tex]
Conclusion: The product of this sequence of reactions is ethyl alcohol (ethanol).
The correct multiple-choice option to prepare ethyl alcohol from a Grignard reagent is (a) HCHO (formaldehyde).
