The organic molecules shown here are derivatives of benzene in which six-membered rings are 'fused' at the edges of the hexagons.
(b) Suppose you are given a sample of one of the compounds. Could combustion analysis be used to determine unambiguously which of the three it is?

Key Concepts

Combustion Analysis

Combustion analysis is a technique used to determine the elemental composition of organic compounds. In this method, a sample is burned in excess oxygen, producing carbon dioxide and water. By measuring the amounts of these products, one can calculate the ratios of carbon and hydrogen in the original compound, which can help identify the compound's structure.

Isomerism

Isomerism refers to the phenomenon where compounds have the same molecular formula but different structural arrangements or spatial orientations. In the context of fused benzene derivatives, isomers can exhibit distinct physical and chemical properties, which may affect their combustion products. Understanding isomerism is crucial for interpreting combustion analysis results.

Molecular Formula vs. Structural Formula

The molecular formula indicates the number and types of atoms in a compound, while the structural formula shows how these atoms are arranged. In combustion analysis, knowing the molecular formula is essential, but distinguishing between different structural isomers is necessary to determine the specific compound. This distinction is vital when analyzing combustion products to identify the original compound.