Question

Which one is the Swarts reaction from the following?
(A) $C{H_3}Br + Nal\xrightarrow{{Acetone}}C{H_3}l + NaBr$
(B) $C{H_3}Cl + Nal\xrightarrow{{Acetone}}C{H_3}l + NaCl$
(C) $C{H_3}Br + AgF \xrightarrow C{H_3}F + AgBr$
(D) $2C{H_3}Cl + 2Na\xrightarrow{{Dryether}}C{H_3}.C{H_3} + 2NaCl$

Answer 1

Hint: In halogen exchange reaction one halogen atom is substituted by another halogen atom. Generally, halogen with smaller atomic size is substituted by halogen with greater atomic size.

Complete Step by Step Solution:
Alkyl chlorides or bromides when treated with $NaI$in presence of dry acetone gives alkyl iodide. This reaction is known as the Finkelstein reaction.
In the given question following examples of Finkelstein reactions are given.
$C{H_3}Br$ $ + $ $NaI$ $\xrightarrow{{Acetone}}$ $C{H_3}I$ $ + $ $NaBr$
$C{H_3}Cl$ $ + $ $NaI$ $\xrightarrow{{Acetone}}$ $C{H_3}I$ $ + $ $NaCl$
Alkyl fluorides cannot be prepared by this method.
Alkyl fluorides are prepared by heating alkyl bromide or chloride in presence of metallic fluoride like $AgF,Sb{F_3}$ or $H{g_2}{F_2}.$.This reaction is known as Swarts reaction.
In given question
$C{H_3}Br + AgF \to C{H_3}F + AgBr$ is an example of Swarts reaction.

Therefore, from the above explanation the correct option is (C) $C{H_3}Br + AgF \to C{H_3}F + AgBr.$

Additional Information:
The reaction,
$2C{H_3}Cl + 2Na\xrightarrow{{Dryether}}C{H_3}.C{H_3} + 2NaCl$
During a reaction ethane is formed from methyl chloride. This is the Wurtz reaction.
In Swarts reaction:
i. Higher alkanes are formed from lower alkyl halide.
ii. Alkanes with an even number of carbon atoms are formed.
iii. Reaction takes place in the presence of dry ether because sodium is very reactive metal if it forms oxide with water.

Note:
1. Swarts reaction is a simple nucleophilic substitution reaction.
2. The mixture of antimony trifluoride and chlorine $(Sb{F_3} + C{l_2})$ is known as Swarts reagent.
3. Generally, alkyl fluorides can be prepared by Swarts reaction. This is a simple halogen exchange method.
4. Halogen of smaller atomic size replaced by halogen of greater atomic size.
Atomic size of Halogen are $I > Br > Cl > F.$