Question

What is the number of isomers possible that may have a benzene ring and a molecular formula \(\mathrm{C}_{\gamma} \mathrm{H}_{9} \mathrm{~N} ?\)

Short answer

There are 5 possible isomers for the given compound.

Step-by-step solution

Understand the Formula

The molecular formula given is \(\mathrm{C}_{6}\mathrm{H}_{9}\mathrm{~N}\). This indicates that we have a benzene ring (\(\mathrm{C}_{6}\mathrm{H}_{5}\)\(()\) as a basic structure. The remaining part of the molecular formula is \(\mathrm{C}_{1}\mathrm{H}_{4}\mathrm{~N}\) that suggests substitutions to the benzene ring.

Identify possible structures

Consider the possibilities to attach an \(\mathrm{NH}_2\), \(\mathrm{CH}_3\), and \(\mathrm{H}_\) groups to the benzene ring. \(\mathrm{NH}_2\) is an amino group while \(\mathrm{CH}_3\) is a methyl group. These can be combined in different positions around the benzene ring to form different structures.

Count the structural isomers

For the molecular formula \(\text{C}_6\text{H}_9\text{N}\), there are 3 primary structures that can be formed: aniline (phenylamine), N-methylaniline (the methyl group attached to nitrogen), and o/ m/ p-toluidine (methyl group attached to the benzene ring in ortho, meta or para positions). Each position of substitution relative to other groups on the ring offers different isomers.

Key concepts

Molecular Formula

In chemistry, a molecular formula is an expression that conveys the number and types of atoms in a molecule. The formula \( \mathrm{C}_{6}\mathrm{H}_{9}\mathrm{~N} \) specifically indicates that this compound contains six carbon atoms, nine hydrogen atoms, and one nitrogen atom. To better understand the molecular formula, it's useful to think of it as a recipe. Each component has a fixed role and number, much like ingredients listed in a recipe.

• The six carbon atoms are typically assumed to form a strong framework, often a benzene ring in aromatic compounds.
• The nine hydrogen atoms must be distributed across the structure.
• Finally, the nitrogen atom usually indicates the presence of a functional group like an amino group.

This formula is a starting point for understanding how different isomers, or molecules with the same formula but different structures, can be constructed. The challenge and intrigue lie in rearranging these atoms in multiple configurations to achieve distinct isomers.

Benzene Ring Structure

The benzene ring is a fundamental concept in organic chemistry. It consists of six carbon atoms connected in a planar, hexagonal ring, with alternating double bonds between them. This configuration bestows the benzene ring with remarkable stability and unique chemical properties.

• Benzene itself is represented as \( \text{C}_6\text{H}_6 \), with each carbon atom bonded to a hydrogen atom.
• For the given molecular formula, the benzene ring serves as the backbone to which other groups are attached.
• The characteristic feature of benzene is its resonance stability, which means its electrons are delocalized over the entire ring structure, providing added stability.

Understanding the benzene ring is crucial in identifying how additional atoms or groups can be positioned, which directly affects the number of possible isomers. The ring structure remains unchanged as different groups are substituted.

Functional Group Substitution

In the context of benzene isomers, functional group substitution refers to replacing one or more hydrogen atoms on the benzene ring with other atoms or groups. Substitution is key to creating isomers because the position and type of substituents determine the structural uniqueness of each isomer.

• An amino group, denoted \( \text{NH}_2 \), can be attached to the benzene ring, forming aniline or phenylamine when placed on a carbon atom of the ring.
• A methyl group, represented as \( \text{CH}_3 \), can also be attached, leading to structures like toluidines where the methyl group is positioned at various points (ortho, meta, para).
• Different orientations of these substitutions result in varied isomers, each with distinct chemical and physical properties.

These substitutions are never random and are often studied in specific positions around the benzene ring, strategically influencing the number and characteristics of the possible isomers.