Question

Draw and name the three isomers of the solvent xylene, \(\mathrm{C}_{6} \mathrm{H}_{4}\left(\mathrm{CH}_{3}\right)_{2}\).

Short answer

The three isomers are ortho-xylene, meta-xylene, and para-xylene.

Step-by-step solution

Understanding Xylene

Xylene is an aromatic hydrocarbon based on the benzene ring structure with two methyl groups \((CH_3)\) attached. The chemical formula for xylene is \(C_6H_4(CH_3)_2\).

Identifying Isomer Possibilities

Xylene has several structural isomers due to the different positions the methyl groups can occupy on the benzene ring. Specifically, the isomers differ in the relative positions of the two methyl groups around the benzene ring.

First Isomer - o-Xylene

The first isomer is ortho-xylene (o-xylene), where the two methyl groups are attached to adjacent carbon atoms on the benzene ring. This means they occupy the 1,2 positions. Draw a benzene ring and place the methyl groups on carbons 1 and 2.

Second Isomer - m-Xylene

The second isomer is meta-xylene (m-xylene), where the two methyl groups are separated by one carbon atom on the benzene ring. This configuration places them at the 1,3 positions. Draw a benzene ring and place the methyl groups on carbons 1 and 3.

Third Isomer - p-Xylene

The third isomer is para-xylene (p-xylene), with the methyl groups on opposite sides of the benzene ring, separated by two carbon atoms. This configuration places them at the 1,4 positions. Draw a benzene ring and place the methyl groups on carbons 1 and 4.

Key concepts

Aromatic Hydrocarbons

Aromatic hydrocarbons are a unique class of hydrocarbons that feature a cyclic, planar structure that allows for resonance stabilization. This resonance gives the molecules certain stability and allows them to experience distinctive reactions compared to other hydrocarbons. A fundamental characteristic of aromatic hydrocarbons is the presence of a benzene ring.
- These compounds typically emit a sweet or pleasant odor, which is a trait linked to the term "aromatic."- They exhibit significant resonance energy due to the delocalization of \(\pi\)-electrons within the ring.
Xylene is an example of aromatic hydrocarbons and is prominently utilized in industrial settings, particularly due to its effective solvent properties. Understanding the properties of aromatic hydrocarbons like xylene can be pivotal in diverse chemical applications, ensuring efficient industrial processes.

Benzene Ring Structure

The benzene ring structure is a vital aspect of aromatic hydrocarbons. It comprises six carbon atoms arranged in a hexagonal ring, with alternating single and double bonds. However, due to resonance, all carbon-carbon bonds are identical, possessing equal bond lengths.
- Benzene is often represented as a hexagon encircled by a circle to symbolize this electron delocalization. - The bond angles within the benzene ring are all 120 degrees, indicating a perfectly planar structure.
This stable, symmetric nature of the benzene ring makes it a pivotal component in the structure of various aromatic compounds. Within this structure, substituents like methyl groups can attach at specific positions, giving rise to different isomers, such as xylene isomers, by altering the spatial arrangement of these groups.

Methyl Group Positioning

In the context of xylene isomers, the positioning of methyl groups on the benzene ring is crucial as it determines the specific isomer.
- **Ortho-xylene (o-xylene):** The two methyl groups are on adjacent carbon atoms in the benzene ring, denoting a 1,2 relationship. - **Meta-xylene (m-xylene):** In this configuration, the methyl groups are separated by one carbon, registering a 1,3 arrangement. - **Para-xylene (p-xylene):** The methyl groups are on opposite ends, depicting a 1,4 relationship.
These different positions affect the physical and chemical properties of each isomer, making them suitable for various industrial applications. Understanding how substituents like methyl groups impact the benzene ring provides valuable insight into the behavior and distinction of organic compounds.