Answer :
Final answer:
The Grignard reaction typically involves two steps when reacting with carbonyl compounds, resulting in the formation of tertiary alcohols from esters and varying types of alcohols from other carbonyl compounds. The Grignard reagent is first formed, then it adds twice to a carbonyl compound, and the reactions lead to the formation of 1º, 2º, or 3º alcohols. option a,b,c,d.
Explanation:
Grignard reagents are highly nucleophilic organometallic compounds that are used to form carbon-carbon bonds in organic synthesis. When a Grignard reagent is added to a carbonyl compound like an ester or a ketone, the reaction usually occurs twice, once to replace the Cl or OEt group, and a second time to convert a ketone intermediate to an alcohol. This sequence of reactions includes Grignard formation, nucleophilic addition, and reduction to alcohol, potentially followed by acetal formation if the alcohol reacts further.
Different types of alcohols can be synthesized depending on the carbonyl compound used. For example, formaldehyde will yield 1º alcohols, aldehydes produce 2º alcohols, and ketones usually result in 3º alcohols. Specific to esters, the reaction with a Grignard reagent results in a 3º alcohol as the main product along with a side product of a 1° alcohol.
This is because the first reaction replaces the OR' group of the ester with an alkyl group forming a ketone, which is then attacked by a second molecule of the Grignard reagent. Upon neutralization with aqueous acid, the final product is a tertiary alcohol with two identical alkyl groups derived from the Grignard reagent.
Grignard reagents can also react with small epoxides like ethylene oxide to generate primary alcohols that have two more carbon atoms than the Grignard reagent itself, which is a valuable method for chain elongation in organic synthesis.
