Question

What is Frankland reagent?

Answer 1

Hint: Frankland reagent is an organometallic reagent which finds its application in organic synthesis. This reagent is used in coupling reactions that lead to carbon-carbon bond formation similar to the Wurtz coupling reaction.

Complete answer:
Organic chemistry utilizes a lot of chemical compounds that do not act as reactants but participate in the reaction. These compounds act as aids through which the reactants are transformed into products. These compounds or complexes are known as reagents.
Frankland reagent is one such important organic reagent that was named after the scientist Edward Frankland who synthesized it. It is an organometallic compound containing two ethyl groups attached to a single zinc metal. This organozinc compound is pyrophoric and very reactive in nature.
Zinc being a metal is electropositive in nature and the ethyl groups are slightly electronegative. Hence there is a polarity in the compound due to which the Frankland reagent readily releases alkyl groups in its reactions.
Edward synthesized this reagent by treating zinc metal with alkyl halides that resulted in the formation of a dialkyl zinc compound (known as the Frankland reagent).
\[2{C_2}{H_5} - X + 2Zn \to {({C_2}{H_5})_2}Zn + Zn{X_2}\]
Here \[{({C_2}{H_5})_2}Zn\] is the Frankland reagent.
This organozinc compound is used in a variety of reactions. The most common application of this reagent is to carry out the coupling of two alkyl groups to form a higher alkane from alkyl halides. The reaction can be written as follows:
\[R - X\xrightarrow{{{{({C_2}{H_5})}_2}Zn}}R - {C_2}{H_5} + {C_2}{H_5}ZnX\]
Where, \[R - {C_2}{H_5}\] is the new alkane formed in the reaction.
Hence the Frankland reagent is \[{({C_2}{H_5})_2}Zn\] and is utilized in carbon-carbon bond formation reactions.

Note:
Other organometallic reagents like Grignard reagent, organolithium reagents and organocopper reagents also supply alkyl groups in the reaction yet they are used for different purposes. Organozinc reagents are comparatively mild and do react as vigorously as other organometallic reagents.