Explain why dialkylcadmium is considered
superior to Grignard reagent for the preparation
of a ketone from an acid chlorine?

Explanation

Since Cd(E.N.=1.7) is less electropositive than Mg(E.N.=1.2), therefore, dialkylcadmiums are less reactive than Grignard reagents towards nucleophilic addition reactions. As such, dialkylcadmiums reacts with the more reactive aciid chlorides to give ketones but do not react further with the less reactive ketones thus formed to give tert-alcohols. In contast, Grignard reagents being more reactive not only reacts with the acid chlorides but also with the ketones so formed to give tert-alcohols.
`underset("Ketone")(R'-overset(O)overset(||)(C)-R) underset(-RCdCl)overset(R_(2)Cd)larr underset("Acid chloride")(R'-overset(O)overset(||)(C)-Cl) unerset(-Mg(Cl)X)overset(RMgX)to underset("Ketone")(R'-overset(O)overset(||)(C)-R) underset((ii)H^(+)//H_(2)O)overset((i)RMgX)to underset(3^(@)" alcohol")(R'-underset(R)underset(|)overset(OH)overset(|)(C)-R)`.