Explain Gomberg reaction with mechanism.

The Gomberg reaction, named after its discoverer Moses Gomberg, is a chemical reaction that involves the generation of trivalent organic radicals (species with an unpaired electron) from aromatic compounds. This reaction is important in the field of organic chemistry because it provided evidence for the existence of organic radicals and contributed to the understanding of their reactivity.

The Gomberg reaction can be summarized as follows:

Aryl Triarylmethylides (Triphenylmethyl Radicals) <--> Arenes + Triphenylmethyl Radical

Here's a step-by-step mechanism for the Gomberg reaction:

Initiation:
The reaction typically starts with the generation of a triphenylmethyl radical (also known as a triarylmethylide radical or a Gomberg radical) through the homolysis (breaking of a covalent bond with one electron going to each atom) of a triarylmethyl halide compound (often a triarylmethyl chloride or bromide) using a radical initiator such as a peroxide (ROOR):

Initiation

Propagation:
Once a triphenylmethyl radical is formed, it can react with another aromatic compound to form a new triphenylmethyl radical and a new aromatic radical:

Propagation

This new aromatic radical can then react with another triphenylmethyl radical to continue the propagation step.

Termination:
The process can continue until termination steps occur. Termination usually involves the combination of two radicals to form a stable molecule:

Termination

Overall, the Gomberg reaction demonstrates the generation and reactivity of organic radicals, confirming their existence and providing insight into their role in various radical-based reactions. It's important to note that while the Gomberg reaction was historically significant, it's not widely used in modern synthetic organic chemistry due to challenges associated with controlling radical reactions and obtaining desired products with high selectivity.