Question

Write a short nots on coupling reaction.

Answer 1

A coupling reaction in organic chemistry is a general term for a variety of reactions where two hydrocarbon fragments are joined together with the aid of a metal catalyst. In one important reaction type a main group organometallic compound of the type RM (R = organic fragment, M = main group centre) reacts with an organic halide of the type R'X with formation of a new carbon-carbon bond in the product R-R'

Richard F. Heck, Ei-ichi Negishi and Akira Suzuki were awarded the 2010 Nobel Prize in Chemistry for developing palladium catalyzed cross coupling reactions

Broadly speaking, two types of coupling reactions are recognized:

Heterocouplings couple two different partners, such as in the Heck reaction of an alkene (RC=CH) and an alkyl halide (R'-X) to give a substituted alkene (RC=CR').

Homocouplings couple two identical partners, as in the Glaser coupling of two acetylides (RC≡CH) to form a dialkyne (RC≡C-C≡CR).

Answer 2

Coupling reactions :

Benzene diazonium chloride reacts with electron rich aromatic compounds like phenol, aniline to form brightly coloured azo compounds.