The refluxing of the silver salt of the carboxylic acid in \(\mathrm{CCl}_{4}\) to form haloalkane or haloarene is called (a) Friedel-Crafts reaction (b) Wittig reaction (c) Hoffimann's bromamide reaction (d) Hunsdiecker reaction

Silver salts of carboxylic acids, often denoted as silver carboxylates, are key intermediates in a classic organic transformation known as the Hunsdiecker reaction.

Silver carboxylates are prepared by treating a carboxylic acid with silver oxide, resulting in the exchange of the hydrogen ion from the carboxyl group (-COOH) with a silver ion (Ag+). This forms a coordination complex where the carboxylate anion is bonded to the silver cation.

The significance of the silver salt in this reaction lies in its ability to readily undergo decarboxylation when exposed to halogenating agents. During the process, the silver ion facilitates the loss of the carboxyl group as carbon dioxide (CO_2), leaving behind a highly reactive carbonium ion. It is this carbonium ion that eventually gets transformed into the desired haloalkane or haloarene via nucleophilic substitution by a halide ion.

Haloalkanes, also known as alkyl halides, are compounds containing an alkyl group attached to a halogen atom. Synthesis of haloalkanes typically involves the substitution of a hydrogen atom in an alkane with a halogen.

However, in the context of the Hunsdiecker reaction, the synthesis of haloalkanes takes a unique pathway. Starting from a silver carboxylate, the reaction proceeds through a radical chain mechanism initiated by light or heat. Here, a halogen molecule abstracts a radical from the silver carboxylate, resulting in the formation of a radical intermediate.

Ultimately, the radical intermediate decomposes, releasing CO_2 and forming a carbon radical, which rapidly combines with the remaining halogen atom to form the haloalkane. This method is particularly useful for synthesizing haloalkanes with a higher level of molecular complexity that may be difficult to achieve through direct halogenation of alkanes.

Haloarenes, or aromatic halides, are aromatic compounds where one or more hydrogen atoms bonded to an aromatic ring have been substituted by a halogen. The Hunsdiecker reaction represents a viable pathway for the synthesis of haloarenes from silver salts of carboxylic acids.

During the reaction, silver carboxylate interacts with a halogen source under conditions that promote decarboxylation, leading to the generation of a phenyl radical in the case of aromatic carboxylic acids. This radical subsequently captures a halogen atom to form the haloarene.

The advantage of this method is that it is applicable to a wide range of aromatic compounds, and it can be used to introduce halogens selectively onto the aromatic ring, which can then be further manipulated in subsequent chemical reactions. This adds a significant tool to the chemist's arsenal for the synthesis of complex organic molecules.