Difference between benzaldehyde and phenylethyl alcohol

Benzaldehyde and phenethyl alcohol are two organic compounds that are often confused, and they have significant differences in chemical structure, physical properties and uses. Distinguishing these two substances not only contributes to safety in daily life, but also plays an important role in chemical experiments and industrial production. This article from the physical properties, chemical properties and identification methods of three aspects, a detailed analysis of how to distinguish between benzaldehyde and phenylethyl alcohol.

1. physical property differences

1. Appearance color The appearance of benzaldehyde and phenylethyl alcohol is very similar, both are colorless liquids, but in some cases can be roughly distinguished by appearance. But because of their different densities, it can be determined by measuring the volume. Benzaldehyde has a density of about 1.08g/cm³, while phenylethyl alcohol has a density of about 0.811g/cm³. Therefore, if the two are poured into the same container, the higher density is benzaldehyde, and the lower density is phenylethyl alcohol.

2. Smell Benzaldehyde has a pungent odor, similar to the taste of burnt feathers, while phenylethyl alcohol is softer than benzaldehyde and has a typical alcoholic smell. This odor difference can be used as a basis for preliminary judgment in actual operation.

3. Solubility Benzaldehyde has low solubility in water and high solubility in organic solvents, especially with benzene-containing organic solvents such as toluene. Phenylethyl alcohol has a high solubility in water, but its solubility in organic solvents is not as good as benzaldehyde.

2. chemical differences

1. chemical reaction tendency Benzaldehyde contains an aldehyde group, which is reductive and prone to reduction reactions. For example, under acidic conditions, benzaldehyde can react with sodium hydroxide solution to form a salt of benzyl alcohol and formaldehyde. However, phenylethyl alcohol has no aldehyde group, and its chemical properties are relatively stable, and similar reactions do not occur.

2. chemical structure From the chemical structure, there is an aldehyde group (-CHO) in the molecular structure of benzaldehyde, and a hydroxyl group (-OH) in the molecular structure of phenylethyl alcohol. This structural difference results in their very different physical and chemical properties.

3. Products after the reaction If these two substances are oxidized, benzaldehyde will be oxidized to benzoic acid, and phenylethyl alcohol will be oxidized to phenylacetic acid. Because the products are different, the identity of the original material can be judged by the subsequent reaction.

3. identification method

1. density measurement method Two substances can be effectively distinguished by measuring their densities. Under the same temperature and pressure conditions, use a densitometer (such as a shaker) to measure the density of the two liquids. The denser one is benzaldehyde, and the denser one is phenylethyl alcohol.

2. Solubility Test The two substances were added to different solvents and their dissolution was observed. For example, the two substances are added to water, and their dissolution rate and amount are observed. The greater solubility is benzaldehyde, and the smaller solubility is phenylethyl alcohol.

3. Odor test Taste, as an aid, can sense the difference between the odors of two substances through the sense of smell. Pour the two into the test tube, gently shake, smell the smell, the stimulation is more obvious for benzaldehyde, more mild for phenylethanol.

4. Chemical Reaction Testing In the laboratory, these two substances can be identified by introducing a chemical reaction. For example, sodium hydroxide solution is added to the two substances respectively, and the reaction phenomenon is observed. The obvious reduction reaction was benzaldehyde, while no obvious reaction was phenylethanol.

5. Ignition Test Another method is through the ignition test. The two substances are respectively close to the flame to observe the combustion. Due to the reductive nature of benzaldehyde, different combustion phenomena may occur in the flame, while phenylethyl alcohol is more stable.

4. summary

Through the above analysis, it can be seen that there are significant differences in physical and chemical properties between benzaldehyde and phenylethanol, mainly reflected in the density, solubility, chemical reaction tendency and molecular structure. Mastering these identification methods can help us accurately distinguish these two substances and avoid potential safety hazards caused by misuse. In practice, physical experiments and chemical reactions can also be combined to achieve more accurate identification. By understanding the difference between the two in depth, we can be more handy in our daily life and work.