To design a retrosynthesis for the synthesis of 2-ethyl-3-methylcyclopent-2-enone using the Grignard reaction as the key step, we need to first identify the functional groups present in the target molecule and then work backward to simpler precursors.Target molecule: 2-ethyl-3-methylcyclopent-2-enoneStep 1: Identify the key functional groups- Carbonyl group C=O - Alkene group C=C - Ethyl and methyl substituentsStep 2: Retrosynthetic analysisSince we want to use the Grignard reaction as the key step, we need to disconnect the molecule at the carbonyl group. This will give us a ketone and an alkyl group. The alkyl group will be derived from the Grignard reagent.Retrosynthetic disconnection:2-ethyl-3-methylcyclopent-2-enone <---> cyclopent-2-enone + ethylmagnesium bromideStep 3: Synthesis plan1. Preparation of the Grignard reagent: Ethylmagnesium bromide can be prepared by reacting ethyl bromide with magnesium in anhydrous ether.Reagents and conditions:- Ethyl bromide CH3CH2Br - Magnesium Mg - Anhydrous ether2. Grignard reaction: The prepared ethylmagnesium bromide can then be reacted with cyclopent-2-enone to form the target molecule, 2-ethyl-3-methylcyclopent-2-enone.Reagents and conditions:- Cyclopent-2-enone- Ethylmagnesium bromide prepared in step 1 - Anhydrous ether- Hydrochloric acid HCl or water to quench the reactionOverall synthesis:1. CH3CH2Br + Mg CH3CH2MgBr in anhydrous ether 2. Cyclopent-2-enone + CH3CH2MgBr 2-ethyl-3-methylcyclopent-2-enone in anhydrous ether, followed by quenching with HCl or water