Question

Give some examples of molecules containing "fused" benzene rings.

Short answer

Examples of molecules containing fused benzene rings include naphthalene (\(C_{10}H_{8}\)), anthracene (\(C_{14}H_{10}\)), and phenanthrene (\(C_{14}H_{10}\)). In naphthalene, two benzene rings share two carbon atoms, while anthracene and phenanthrene both consist of three fused benzene rings with different arrangements.

Step-by-step solution

Example 1: Naphthalene

Naphthalene is a molecule consisting of two fused benzene rings, sharing two carbon atoms. Its chemical formula is \(C_{10}H_{8}\), and its structure can be represented as: ``` C1-C2-C3-C4-C5 \\ | C10==C9-C8 \ / C7 | C6 ```

Example 2: Anthracene

Anthracene is another molecule containing fused benzene rings; in this case, three benzene rings are fused together. Its chemical formula is \(C_{14}H_{10}\) and its structure can be represented as: ``` C1-C2-C3-C4-C5 \\_ | C14==C9==C8-C7 \| | C10-C11-C12-C13 ```

Example 3: Phenanthrene

Phenanthrene is another example of a molecule containing fused benzene rings. Like Anthracene, it also consists of three benzene rings, but the arrangement of the rings is different. Its chemical formula is \(C_{14}H_{10}\) and its structure can be represented as: ``` C1-C2-C3-C4-C5 \\ | C14==C9-C8 X C7 | C6 ``` In conclusion, we have provided three examples of molecules containing fused benzene rings, which are naphthalene, anthracene, and phenanthrene.

Key concepts

Naphthalene

Naphthalene is a well-known organic compound, easily identified by its distinct smell, most commonly associated with mothballs. It is a simple aromatic hydrocarbon featuring a pair of benzene rings that share two carbon atoms, thus forming a structure known as fused benzene rings.

The chemical structure of naphthalene is \[ C_{10}H_{8} \] where the rings are fused such that they create a single compound. This structure provides naphthalene with its characteristic planar shape and contributes significantly to its chemical behavior, including its aromaticity.

• Aromaticity is the concept where cyclic, planar structures with conjugated bonds exhibit enhanced stability.
• In simple terms, aromatic compounds like naphthalene tend to be more stable than their non-aromatic counterparts.
• This stability is due to delocalized electrons above and below the plane of the atom.

Naphthalene’s utility extends to numerous applications, such as in the production of dyes, resins, and as a fumigant in pest control. Its unique properties are derived from its fused structure, making it a key example when discussing fused benzene rings.

Anthracene

Anthracene is another fascinating example of fused benzene rings. This compound consists of three benzene rings lined up in a linear arrangement. Each ring shares a pair of carbon atoms with its neighbor, resulting in a contiguous sequence of aromatic rings.

The chemical formula for anthracene is \[ C_{14}H_{10} \] reflecting its structure made from a series of fused benzene rings. The alignment of the rings in anthracene provides it with unique optical and electronic properties.

• Anthracene is often used in the manufacturing of dyes and plastics.
• Additionally, its aromatic nature makes it useful in organic light-emitting diodes (OLEDs).
• The linear morphology of anthracene contributes to its solid appearance and high melting point.

The linear tricyclic arrangement in anthracene contributes to more complex interactions compared to smaller aromatic structures like naphthalene, allowing for diverse applications in materials science and engineering.

Phenanthrene

Phenanthrene also showcases three benzene rings, but unlike anthracene, these rings are not linearly arranged. Instead, phenanthrene is structured in a bent shape, providing it with unique chemical characteristics.

The chemical formula of phenanthrene is \[ C_{14}H_{10} \] similar to anthracene but differing in structure. This bent configuration offers phenanthrene different reactivity and properties compared to anthracene.

• Phenanthrene is found in high-temperature environments like coal tar, indicating strong thermal stability.
• Its non-linear arrangement makes it valuable in the study of polymers and as a precursor in the synthesis of other chemicals.
• Its three-ringed structure leads to unique absorption and fluorescence properties, essential in chemical sensing and research applications.

The bent structure of phenanthrene not only alters its physical properties but also influences its interactions, making it versatile for various chemical processes and studies.