How do you distinguish between alcohol and phenol

How to distinguish between alcohol and phenol: chemical characteristics and identification methods

in chemical analysis, alcohol (such as ethanol) and phenol are two common organic compounds, which have obvious differences in appearance, odor and chemical reaction. How to distinguish between alcohol and phenol? This article will analyze their chemical properties, physical properties and common identification methods in detail.

1. alcohol and phenol chemical structure difference

The difference in chemical structure between alcohol and phenol is the root cause of the difference in their properties. Alcohol is an organic compound containing a hydroxyl (-OH) functional group with a hydroxyl group attached to an alkyl group in the molecule (for example, ethanol has the formula C₂ H∞OH). Phenol, on the other hand, is a hydroxyl derivative of the benzene ring structure, with the molecular formula C- HHY-OH, where the benzene ring is attached to a hydroxyl group. This structural difference makes alcohol and phenol different in the nature of the reaction.

2. Physical Properties Comparison

Alcohol and phenol are obviously different in physical properties, which allows us to distinguish them through some simple experiments in actual operation.

1. Odor: Alcohol usually has a weak pungent smell, while phenol has a unique pungent smell, similar to the smell of disinfectant or tar. This difference can be quickly distinguished by the sense of smell.

2. Solubility: Alcohol has good water solubility and is usually fully miscible with water at room temperature, while phenol is not easy to completely dissolve in water. Its solubility in water is low, forming a partial solution.

3. Boiling point and melting point: The boiling point of alcohol (such as ethanol is 78°C) is significantly lower than the boiling point of phenol (181°C). Therefore, they can be preliminarily distinguished by the boiling point test.

3. chemical reactions are different

The performance of alcohol and phenol in chemical reactions is also an effective means of distinguishing them.

1. Reaction with oxidants: alcohol in the strong oxidant (such as potassium permanganate or hydrogen peroxide) under the action of oxidation reaction, the generation of aldehyde or acid, and phenol can be in the strong oxidant under the action of oxidation to a higher price of benzoquinone substances. This reaction can help distinguish between the two.

2. Reaction with potassium ferricyanide: Phenol appears purple when it reacts with potassium ferricyanide solution, while alcohol does not have this reaction. Therefore, the potassium ferricyanide reagent is a simple and effective discrimination tool.

3. The difference of acid-base properties: phenol has a certain acidity (pKa is about 9.95), which can react with strong alkali to generate phenoxide, while alcohol shows weak acidity and is not easy to react with alkali.

4. laboratory common identification methods

In the laboratory, in addition to distinguishing alcohol and phenol based on physical properties and chemical reactions, the following simple experimental methods can also be used to distinguish:

1. Purple reaction reagent method: as mentioned above, add potassium ferricyanide solution to the liquid to be tested. If purple appears, it can be confirmed that the substance is phenol, and if there is no purple reaction, it is alcohol.

2. Solubility method: Dissolve the test substance in water and observe the solubility. If the substance is completely dissolved and has no peculiar smell, it is more likely to be alcohol; if it is less soluble and has a pungent smell, it is most likely to be phenol.

3. Oxidation reaction observation method: potassium permanganate solution was used to detect the oxidation reaction of the sample. If the solution changes color or reacts violently, it can be preliminarily judged as alcohol; the reaction of phenol is relatively slow.

5. summary

Through the above analysis, we can find that "how to distinguish between alcohol and phenol" is not a difficult problem. We can easily distinguish these two chemicals by comparing their chemical structures, physical properties, and reaction characteristics. In practice, combined with regular laboratory detection methods, such as potassium ferricyanide reaction method, solubility method and oxidation reaction method, alcohol and phenol can be more accurately and efficiently distinguished.

Whether it is chemical identification in daily life or chemical research in the laboratory, understanding how to distinguish between alcohol and phenol is a very important skill.