Question

Converstion between 2cloro butane into 2methyl butanoic acid

Answer 1

2-chlorobutane -----> Cl-Mg-butane using Mg metal in ether.

The magnesium metal inserts itself between the chlorine atom and carbon 2 atom of butane.

Now, carboxylation of a grignard gives you a carboxylic acid:

Cl-Mg-butane --------> 2-methylbutanoic acid using 1. CO2, ether and then 2. H3O+.

CO2 takes the place of the MgCl at the 2 position of butane, and once you add a proton source (H3O+) it becomes a carboxylic acid.

The carbon of the newly added COOH becomes part of the backbone of the molecule and using the proper nomenclature rules, now you have 2-methylbutanoic acid.