Wurtz Fittig Reaction Mechanism

Carbon is the most important compound in the periodic table, as it is useful for everything and serves as the foundation for all chemical sciences. The Wurtz–Fittig reaction was discovered with the help of this tetravalent and unique compound.

The Wurtz reaction was discovered by Charles Adolphe Wurtz in the year 1855. A new carbon–carbon bond was formed, which was followed by a coupling reaction between two alkyl halides.In the year 1860, another scientist, Wilhelm Rudolph Fitting, expanded on this. As a result, the reaction is dubbed the Wurtz–Fittig reaction.Fitting combined an alkyl halide with an aryl halide, rather than two alkyls. Asymmetric products are the best candidates for this reaction. It is one of the most important organic chemistry reactions for forming carbon–carbon bondIn the presence of dry ether, aryl halide reacts with alkyl halide to form alkyl substituted benzene. Ethane and biphenyl are also formed in small amounts in this reaction.

What is the Wurtz–Fittig Reaction and how does it work?

The Wurtz–Fittig reaction occurs when an alkyl halide reacts with an aryl halide and sodium metal in the presence of dry ether to form substituted aromatic compounds by forming a new carbon–carbon bond. The following is the reaction: It’s a reaction of coupling. It’s a tweaked version of the Wurtz reaction. Wurtz reaction is an organometallic chemistry coupling reaction in which two alkyl halides react with sodium metal in the presence of dry ether to form a higher alkane by forming a new carbon–carbon bond. The following is Wurtz’s response –

2 R-X + 2 Na -> R-R + 2 Na+X-

R stands for alkyl group.

X stands for the halide ion.

If the relative chemical reactivities of the halide reactants are different, the Wurtz–Fittig reaction is best for the formation of asymmetrical products. The reaction is primarily used for the alkylation of aryl halides, but it can also be used to make biphenyl compounds when ultrasound is used.

Fittig Reaction

Wurtz–Fittig retaliates in two ways. The first one is the one described above, and the second one can be defined as follows:

In the presence of dry ether, two molecules of aryl halide react with sodium metal to form diphenyl.

Aside from sodium, a variety of other metals can be used to create similar products. Potassium, iron, copper, and lithium are among these elements. In order to obtain the product when using lithium, the reaction requires the presence of ultrasound.

Wurtz–Fittig Reaction Mechanism

Let’s look at an example to better understand the Wurtz–Fittig reaction.

Take a look at the generic reaction below.

Sodium metal reacts separately with two types of halides to form aryl sodium and alkyl sodium in this reaction.

The more reactive alkyl halide first forms an organo sodium, which reacts with an aryl halide as a nucleophile.

The mechanism of the Wurtz–Fittig reaction is unknown because there are two approaches to describing the mechanism of the reaction, both of which have empirical evidence. Below is a list of both approaches –

• Radical mechanism
• Organo-alkali mechanism 

Radical Mechanism

The radical approach involves the formation of aryl radicals and alkyl radicals using sodium as a catalyst. Sodium metal acts as a mediator in this mechanism, resulting in the formation of an alkyl radical and an aryl radical. The alkyl and aryl radicals then combine to create a substituted aromatic compound. The formation of side products, which cannot be explained by the organo-alkali mechanism, supports this mechanism. For example, Bachmann and Clarke discovered that one of the many side products of the reaction of sodium and chlorobenzene is triphenylene, which can only be explained by a free radical mechanism. The reaction mechanism is as follows:

R-X + M → R• + M+X-

R• +M → R-M+

R-M+  + R-X → R-R + M+X-

Mechanism of Organo-Alkali

The organo-alkali approach involves reacting an aryl halide with sodium metal to produce an intermediate organo-alkali compound. According to this method, an aryl halide reacts with sodium metal to form an organo-alkali compound, which is then attacked by a nucleophilic alkyl halide. This mechanism is supported by indirect evidence, such as the fact that an organo-alkali intermediate is formed during the reaction, as many investigators have observed.

Other Metals which can be used instead of Sodium

Other metals, such as copper, iron, potassium, and lithium, can be used in Wurtz–Fittig reactions instead of sodium. When lithium is substituted for sodium, the reaction yields a significant yield, but only under ultrasonic conditions. It occurs as a result of a free radical mechanism.

Wurtz–Fittig Reaction: Applications

In the laboratory, the Wurtz–Fittig reaction is useful for synthesising organosilicon compounds. The Wurtz–Fittig reaction, for example, can be used to make t-butyl trimethoxysilane. In this case, a 40% yield is achieved.

Wurtz–Fittig reactions have a limited number of applications. It isn’t used on a large scale in the industrial sector. It is, however, useful in the synthesis of substituted aromatic compounds in the laboratory.

There aren’t many uses for this reaction. This is due to the side reaction, which undergoes further reorganisation and elimination. This is one of the reaction’s major drawbacks, making it unsuitable for many manufacturing processes.

This reaction is used to make organosilicon, though it is a significant challenge to achieve large-scale production.

It was all about the Wurtz–Fittig reaction in this case.

Conclusion

The chemical reaction of aryl halides with alkyl halides and sodium metal with dry ether present to yield substituted aromatic compounds is called the Wurtz-Fittig reaction for the scientists – Charles Adolphe Wurtz and Wilhelm Rudolph Fittig (Wurtz for the discovery of the carbon-carbon bond formation from the coupling reaction.