Question

When ethylbenzene is reacted with nitric acid, three possible benzenes containing both a nitro group and an ethyl group are obtained. Draw and name them.

Short answer

The compounds are ortho-nitroethylbenzene, meta-nitroethylbenzene, and para-nitroethylbenzene.

Step-by-step solution

Understanding the Reaction

In this reaction, ethylbenzene undergoes nitration. Nitration involves substituting a hydrogen atom on the benzene ring with a nitro group (-NO2) using nitric acid (HNO3) and typically sulfuric acid (H2SO4) as a catalyst.

Analyzing the Ethyl Group's Position

Ethylbenzene has an ethyl group (-C2H5) attached to the benzene ring. The position of substituents in benzene affects where additional groups are added. The ethyl group directs incoming nitro groups to the ortho (o) and para (p) positions due to its electron-donating nature.

Identifying Possible Structures

Three possible positions can be substituted by a nitro group on the benzene ring relative to the ethyl group: ortho, meta, and para. However, due to the directing influence of the ethyl group, we commonly obtain ortho and para isomers.

Drawing and Naming the Compounds

The three possible substituted benzenes are: 1. Ortho-nitroethylbenzene, where the nitro group is adjacent to the ethyl group, 2. Meta-nitroethylbenzene, where the nitro group is one carbon away from the ethyl group, and 3. Para-nitroethylbenzene, where the nitro group is opposite the ethyl group on the ring.

Key concepts

Nitration

Nitration is an important organic reaction often used in the production of explosives, dyes, and pharmaceuticals. It involves the introduction of a nitro group (-NO2) into an organic compound, typically a benzene ring. This is achieved by using a mixture of concentrated nitric acid (HNO3) and concentrated sulfuric acid (H2SO4) as the nitrating agent.

• The sulfuric acid acts as a catalyst, generating the reactive species, the nitronium ion (NO2+), from nitric acid.
• The nitronium ion then attacks the benzene ring, substituting for a hydrogen atom.
• This process requires careful control of temperature and concentration to avoid excessive reactions.

Understanding the fundamentals of nitration enables chemists to manipulate the chemical structure of aromatic compounds selectively, thus producing desired derivatives.

Ethylbenzene

Ethylbenzene is an aromatic hydrocarbon featuring a benzene ring bonded to an ethyl group (-C2H5). It is a significant starting material in the production of styrene, an important monomer for making polystyrene plastics. In organic reactions, such as nitration, the ethyl group influences the reactivity and substitution pattern of the benzene ring.

• The ethyl group is slightly electron-donating due to its alkyl chain, activating the benzene ring towards electrophilic substitution reactions.
• When ethylbenzene undergoes substitution, the ethyl group directs incoming electrophiles such as the nitronium ion to the ortho and para positions.

This directing effect is crucial for predicting and controlling the position of new substituents on the benzene ring, leading to isomeric products that vary in properties and uses.

Benzene Substitution

Benzene substitution refers to the process where one or more hydrogen atoms on the benzene ring are replaced by other atoms or groups. This kind of reaction is essential in organic chemistry for modifying benzene to create a range of aromatic compounds.

• Benzene's stability arises from its aromatic structure, making it less reactive than typical alkenes.
• However, it readily participates in electrophilic aromatic substitution due to its cloud of \(\pi\pi\) electrons above and below the ring, which attracts electrophiles.
• The nature of the substituent already present on the benzene ring affects where new groups are added. Certain groups can direct new substituents to specific locations, known as ortho, meta, and para positions.

By understanding substitution patterns, chemists can design reactions to synthesize a variety of benzene derivatives with particular functionalities.

Nitro Compounds

Nitro compounds are a class of organic compounds that contain one or more nitro groups (-NO2) bound to a carbon atom. These compounds are significant in various chemical industries and play a role in the production of explosives, pharmaceuticals, and dyes.

• The nitro group is a strong electron-withdrawing group, imparting distinct properties to the compounds it is part of.
• When bound to an aromatic ring, such as benzene, it usually deactivates the ring, making it less reactive in further electrophilic substitution reactions.
• Nitro compounds can be reduced to amines, which are important intermediates in many synthetic pathways.

Understanding the chemistry of nitro groups and their influence on molecular reactivity is key for developing efficient synthetic routes in organic chemistry.