Assume that you have samples of the following two compounds, both with formula C₇H₈O. Both compounds dissolve in ether, but only one of the two dissolves in aqueous NaOH. How could you use this information to distinguish between them?

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Identify the functional groups in the two compounds with the formula C₇H₈O. One compound likely contains a phenol group (-OH attached to an aromatic ring), while the other may contain an alcohol group (-OH attached to a non-aromatic carbon). Phenols are acidic, whereas alcohols are not significantly acidic.

Recall that phenols can react with aqueous NaOH because they are weak acids and can donate a proton to form a phenoxide ion, which is soluble in water. Alcohols, on the other hand, do not react with NaOH because they are not acidic enough.

Set up a test: Dissolve a small amount of each compound in ether (a nonpolar solvent). Then, add aqueous NaOH to each solution and observe whether the compound dissolves in the aqueous layer (indicating a reaction).

If the compound dissolves in aqueous NaOH, it is the phenol because it reacts to form the water-soluble phenoxide ion. If the compound does not dissolve in aqueous NaOH, it is the alcohol because it does not react.

Conclude the test by identifying the compound that dissolves in aqueous NaOH as the phenol and the one that does not as the alcohol. This distinction is based on the chemical reactivity of their functional groups with a base.

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주요 개념

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Solubility in Aqueous NaOH

The solubility of a compound in aqueous NaOH indicates its acidic or basic properties. Compounds that can react with NaOH, typically acidic compounds, will dissolve in this basic solution. This property can help differentiate between compounds that may otherwise appear similar, as one may contain a functional group that reacts with NaOH, while the other does not.

Functional Groups

Functional groups are specific groups of atoms within molecules that are responsible for the characteristic chemical reactions of those molecules. In the case of C₇H₈O compounds, the presence of functional groups such as phenols or carboxylic acids can influence solubility in NaOH. Identifying these groups is crucial for understanding the reactivity and solubility behavior of the compounds.

Ether Solubility

Ether solubility indicates that the compounds are likely non-polar or have non-polar characteristics, allowing them to dissolve in organic solvents like ether. This property is important for understanding the overall polarity and potential reactivity of the compounds. While both compounds dissolve in ether, the differing solubility in NaOH provides a means to distinguish between them based on their polar or non-polar functional groups.

Assume that you have samples of the following two compounds, both with formula C7H8O. Both compounds dissolve in ether, but only one of the two dissolves in aqueous NaOH. How could you use this information to distinguish between them?