Question

Which of the following halogen exchange reactions will occur in acetone?
A.$R - I + NaCl \to $
B.$R - F + KCl \to $
C.$R - Cl + NaI \to $
D.$R - F + AgBr \to $

Answer 1

Hint: Halogens are group 17 elements which are non-metallic in nature. They are highly reactive. Finkelstein reaction is $SN_2$ in which one halogen is exchanged with another in the presence acetone. These halogens include chloride and bromide reacting with another alkyl halide like sodium iodide.

Complete Answer:
The non-metallic elements of group 17 of the periodic table are known as halogens. They are highly reactive due to high electronegativity and high effective nuclear charge. Finkelstein reaction is an exchange reaction in which one halogen atom is replaced with another. It is a substitution nucleophilic bimolecular reaction which is known as the SN2 reaction. It takes place in one step where the nucleophile attacks and the leaving group leaves simultaneously. The Finkelstein reaction takes place in the presence of a metal halide.
Acetone is a colourless organic solvent with a chemical formula of ${(C{H_3})_2}CO$ . It is the simplest ketone and is used in household cleaning and for various commercial operations. It is polar and thus it
forms polar electrostatic interactions with water molecules and is soluble in water and even though acetone is liquid at room temperature but it has a density less than water. Acetone reacts with halogens as in the reaction the ketone removes the hydrogen and then ketone reacts with the halogen.
For the above given question, as we know that, Finkelstein reaction takes place in the presence of acetone where an alkyl halide reacts with $NaI$ and the exchange of halogen takes place. Chlorides are insoluble in acetone and chlorides undergo Finkelstein reaction.
 $ R - X + NaI \to R - I + NaX $
Where $X$ is either chloride or bromide.
$ R - Cl + NaI \to R - I + NaCl $

Thus, the correct option is (C).



Note: The lower members of ketone are soluble in water as they form hydrogen bonds with water but the higher members are soluble in organic solvents like benzene. As the size of the chain of the compound increases, the solubility of the ketones decreases.