Assume that you have samples of the following two compounds,...

Assume that you have samples of the following two compounds, both with formula $\mathrm{C}_{7} \mathrm{H}_{8} \mathrm{O} .$ Both compounds dissolve in ether, but only one of the two dissolves in aqueous $\mathrm{NaOH}$. How could you use this information to distinguish between them?

Key Concepts

Ether Functional Group

Ethers consist of an oxygen atom connected to two alkyl or aryl groups and generally lack acidic protons. Due to the absence of ionizable hydrogen atoms near the oxygen, ethers do not react with bases like NaOH. This inertness towards deprotonation means that ethers remain uncharged and typically insoluble in aqueous base, providing a contrast in solubility behavior when compared to phenolic compounds.

Acid-Base Reaction as a Diagnostic Tool

The differing responses of phenolic and ether functional groups to basic conditions can be used as a diagnostic tool to distinguish between compounds with similar molecular formulas. In a base like aqueous NaOH, a phenol will undergo deprotonation to form a soluble phenoxide ion, whereas an ether will not react and remain insoluble. This selective reactivity based on acid-base chemistry is key to identifying the presence or absence of a phenolic group in an unknown sample.

Phenolic Functional Group

Phenols contain a hydroxyl group (-OH) attached directly to an aromatic ring. This structure imparts acidity to phenols because the aromatic system stabilizes the negative charge of the phenoxide ion formed upon deprotonation. This acidic character is significant because it allows phenols to react with bases, such as sodium hydroxide (NaOH), resulting in soluble phenoxide salts in aqueous media.

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