Question:

Why is Wurtz reaction not preferred for the preparation of alkanes containing odd number of carbon atoms? Illustrate your answer by taking one example

Updated On: Nov 18, 2023
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Solution and Explanation

Wurtz reaction is limited for the synthesis of symmetrical alkanes (alkanes with an even number of carbon atoms) In the reaction, two similar alkyl halides are taken as reactants and an alkane, containing double the number of carbon atoms, are formed. Example:
Wurtz reaction

Wurtz reaction cannot be used for the preparation of unsymmetrical alkanes because if two dissimilar alkyl halides are taken as the reactants, then a mixture of alkanes is obtained as the products. Since the reaction involves free radical species, a side reaction also occurs to produce an alkene. For example, the reaction of bromomethane and iodoethane gives a mixture of alkanes.
Wurtz reaction

The boiling points of alkanes (obtained in the mixture) are very close. Hence, it becomes difficult to separate them.

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Concepts Used:

Aromatic hydrocarbon

Aromatic hydrocarbons, sometimes known as arenes, are aromatic organic molecules made up entirely of carbon and hydrogen. In aromatic compounds a benzene ring which is named after the simple aromatic chemical benzene, or a phenyl group when part of a larger structure, is the configuration of six carbon atoms.

Read More: Aromaticity

Reactions of Aromatic Hydrocarbons:

1. Aromatic Substitution Reactions

This reaction involves the replacement of one substituent on the ring of an aromatic hydrocarbon, commonly a hydrogen atom, by a different substituent group.

The common types of aromatic substitution reactions are:

  • Nucleophilic aromatic substitution reactions
  • Electrophilic aromatic substitution reactions
  • Radical nucleophilic aromatic substitution reactions

2. Coupling Reactions

In these types of reactions, the coupling of two fragments that have a radical nature is achieved with the help of a metal catalyst