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Wurtz-Fittig Reaction is a chemical process in which aryl halides react with alkyl halides and sodium metal. The reaction is carried out in the presence of dry ether. Besides sodium, the reaction can be carried out with potassium, iron and copper.
- It will produce an aromatic compound.
- Wurtz-Fittig reaction will result in the formation of a carbon-carbon bond.
- It is also known as a coupling reaction.
- In 1855, Charles Adolphe Wurtz introduced the Wurtz reaction.
- Wurtz reaction involves the combination of two alkyl halides.
- The concept was further extended by Wilhelm Rudolph Fitting in 1860.
- Wurtz reaction was later renamed as the Wurtz-Fittig Reaction.
- It is most commonly used in the biochemical industry.
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Key Terms: Wurtz-Fittig Reaction, Dry Ether, Carbon, Potassium, Aromatic Compound, Aryl Halide, Alkyl Halide, Coupling Reaction, Wurtz Reaction, Benzene
Equation of Wurtz-Fittig Reaction
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Wurtz-Fittig Reaction was discovered with the help of tetravalent carbon compounds in the process of organic chemistry.
- The process of the Wurtz-Fittig reaction can be explained with the help of the radical mechanism and organo-alkali mechanism.
Wurtz-Fittig Reaction
It is preferable for asymmetrical products.
- Aryl halide when reacted with alkyl halide will form alkyl substituted benzene.
- The process is carried out in a dry environment as sodium is highly reactive with oxygen and moisture.
- In case the reactivity of alkyl halide is more than aryl halide, then the organosodium bond is formed first.
- Halogens will help separate the alkyl halide and aryl halide from their respective chemical reactivities.
The chemical reaction used in the Wurtz-Fittig Reaction is as follows:
- 2R – X + 2Na → R – R + 2NaX
- Where R = alkyl group
- X = Halide ion
Common Example of Wurtz-Fittig Reaction
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| Gattermann Reaction | Newlands’s Law of Octaves | Real Gas |
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Mechanism of Wurtz-Fittig Reaction
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Wurtz-Fittig Reaction can be explained by using the radical mechanism and organo-alkali mechanism which is as follows:
Radical Mechanism
In the radical mechanism, sodium-mediated aryl radicals and alkyl radicals are formed by a chemical reaction.
- The reaction is carried out in the presence of sodium, which acts as a mediator.
- The radicals of alkyl and aryl ions combine to form an alkyl-aryl aromatic compound.
- In this reaction, a side product is also formed.
- The most common example of a radical mechanism includes the reaction between sodium and chlorobenzene.
- The reaction between sodium and chlorobenzene was analysed by Bachmann and Clarke.
- It will form a side product named triphenylene.
Radical Mechanism
Organo-Alkali Mechanism
In the organo-alkali mechanism, an intermediate organo-alkali compound is formed. According to the mechanism, aryl halide will react with sodium metal, followed by nucleophilic attack of alkyl halide.
- It is a form of indirect reaction.
- The reaction is carried out in the presence of sodium metal.
- When a mixture of sodium and isobutyl bromide reacts with carbon dioxide, it forms 3-methylbutanoic acid.
Organo-Alkali Mechanism
Example of Wurtz-Fittig Reaction
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Some of the most common examples of Wurtz-Fittig Reaction are as follows:
- When methyl chloride reacts with sodium metal in the presence of dry ether, then sodium chloride and ethane are formed.
The reaction for the process is as follows: 2CH3Cl + 2Na → CH3-CH3 + 2NaCl
- When methyl iodide reacts with sodium metal in the presence of dry ether, sodium iodide and ethane are formed.
The reaction for the process is as follows: 2CH3I + 2Na → CH3-CH3 + 2NaI
Applications of Wurtz-Fittig Reaction
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Wurtz-Fittig has a limited number of applications. Some of the applications of the Wurtz-Fittig Reaction are as follows:
- It is used in the production of the biphenyl compound.
- The reaction is used in the synthesis of organosilicon compounds
- Wurtz-Fittig reaction is used in the synthesis of substituted aromatic compounds.
- It is used in large-scale synthesis of chemical products in one of the biochemical processes.
Limitations of Wurtz-Fittig Reaction
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The limitations involved in the Wurtz-Fittig Reaction are as follows:
- The reaction is not able to produce low alkanes and requires two carbon atoms for the reaction to proceed further.
- It is unsuitable for compounds with an odd number of carbon atoms.
- Wurtz-Fittig reaction cannot be carried out in moisture as sodium is highly reactive with moisture.
- If halides are bulky, it will form too many side products in a reaction.
Things to Remember
- Wurtz-Fittig Reaction is a form of coupling reaction in which aryl halides react with an alkyl halide and sodium metal in the presence of dry ether.
- The reaction was proposed by Charles Adolphe Wurtz and modified by Wilhelm Rudolph Fitting.
- It can be used with other metals such as potassium, lithium, iron and copper.
- The Wurtz-Fittig Reaction can be explained with the help of the organo-alkali mechanism and radical mechanism.
- Though it has limited applications, it is mainly used in biochemical industries.
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Sample Questions
Ques. What is the difference between the Wurtz and Fittig Reaction? (3 marks)
Ans. The differences between the Wurtz and Fittig Reactions are as follows:
| Wurtz Reaction | Fittig Reaction |
|---|---|
| It was proposed by Charles Adolphe Wurtz. | It was proposed by Wilhelm Rudolph Fitting. |
| In this two alkyl halides react with sodium metal to form a higher alkane in the presence of dry ether. | In this two aryl halides react with sodium metal to form diphenyl in the presence of dry ether. |
| The reaction will form asymmetrical alkanes | The reaction will form aromatic biphenyl compounds. |
Ques. What is a Wurtz-Fittig Reaction? (2 marks)
Ans. Wurtz-Fittig Reaction is a popular reaction in organic chemistry in which alkyl and aryl halide react with sodium metal in the presence of dry ether. The resultant product will be aromatic compounds and organosilicon compounds.
The reaction of Wurtz-Fittig is as follows: 2R – X + 2Na → R – R + 2NaX
- Where R = alkyl group
- X = Halide ion
Ques. Give examples of Wurtz-Fittig Reactions. (3 marks)
Ans. The examples of Wurtz-Fittig Reactions are as follows:
- When 1-bromopropane reacts with sodium in the presence of dry ether then the following reaction take place:
CH3CH2CH2Br + 2Na + BrCH3CH2CH2 —---------------> CH3(CH2)4CH3
- When bromobenzene reacts with methyl bromide in presence of sodium and dry ether then toluene will be formed.
C6H5−Br + CH3−Br +2Na ⟶ C6H5−CH3 + 2NaBr
Ques. What are the applications of the Wurtz-Fittig Reaction? (3 marks)
Ans. The applications of the Wurtz-Fittig Reaction are as follows:
- The alkyl halide and aryl halide reach to form biphenyl compounds.
- It is used in biochemical industries for the synthesis of large organic compounds.
- The reaction is used to produce organosilicon compounds and substituted aromatic compounds.
Ques. How many other metals can be used instead of sodium metal in the Wurtz-Fittig Reaction? (1 mark)
Ans. Four other metals can be used instead of sodium in the Wurtz-Fittig Reaction, including potassium, lithium, iron and copper.
Ques. Why is the Wurtz-Fittig Reaction carried out in the presence of dry ether? (2 marks)
Ans. The Wurtz-Fittig Reaction is carried out in the presence of dry ether because alkanes are nonpolar compounds which are highly soluble in dry ether. Next, sodium metal is highly reactive to moisture and can catch fire easily, so these alkanes will not react with sodium.
Ques. Explain the process of formation of the Wurtz-Fittig Reaction step by step. (3 marks)
Ans. The free radical R initiates the process of formation of the Wurtz-Fittig Reaction.
- It involves the exchange of metal and halogen, which results in the formation of carbon-carbon bonds.
- The first step involves forming free radicals by transferring electrons from sodium metal to the halogen atom in alkyl halide. The reaction is as follows:
R – X + Na → R* + Na+ X-
- The alkyl radical formed in the above step will take another atom from sodium metal. It will result in the formation of alkyl anions.
- In the next step, the alkyl anion will displace the halide ion from another alkyl halide. The following reaction is called the SN2 reaction. The reaction is as follows:
R – Na+ + R – X → R – R + Na+ X-
Ques. What are the limitations of the Wurtz-Fittig Reaction? (3 marks)
Ans. The limitations of the following Wurtz-Fittig Reaction are as follows:
- Wurtz-Fittig Reaction will require two carbon atoms to produce low alkanes as the final product.
- No result will be obtained if the number of carbon atoms in the reaction is odd.
- In the Wurtz-Fittig Reaction side, products are formed. The problem arises when halide is bulky as it will form too many side products.
- The process is carried out in a dry environment.
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