Answer
See below.
Work Step by Step
Step 1: The three alkyl bromides in this problem first react with magnesium to form the Grignard reagent. In the Grignard reagent, C atom in the C-Mg bond has a higher electronegativity than Mg, so C atom eventually pulls the electron density towards it. In this way, a carbanion where the negative charge falls on the C atom (R:-), and the cation MgX+ are formed.
Step 2: In a nucleophilic addition reaction, the negative charge from the carbanion (R:-) is donated to the carbon of carbon dioxide (O=C=O) and the electron density from C=O bond is pulled towards the O atom. As a result, a carboxylate anion (RCOO-) is formed.
Step 3: Finally, RCOO- picks up the H+ from the acid added, forming a carboxylic acid RCOOH.
