How to Distinguish Ethanol Acetaldehyde Acetic Acid

In the chemical industry, ethanol, acetaldehyde and acetic acid are three common organic compounds, which are significantly different in chemical properties, physical properties and uses. Distinguishing these three helps to use and distinguish them correctly in different applications. The following will analyze in detail how to distinguish these three substances from several aspects.

1. material structure and group

1. Structure of Ethanol The chemical formula of ethanol is C₂ Hwithin OH, and its molecular structure contains a hydroxyl group (-OH), which makes it a typical alcohol. The presence of hydroxyl groups allows them to exhibit unique characteristics in chemical reactions, such as easy reaction with metallic sodium.

2. Structure of acetaldehyde The chemical formula of acetaldehyde CHO, molecular structure contains an aldehyde group (-CHO). The presence of the aldehyde group allows acetaldehyde to exhibit aldehyde properties in chemical reactions, such as being susceptible to oxidation.

3. Structure of acetic acid The chemical formula of acetic acid is CH, and its molecular structure contains a carboxyl group (-COOH). The presence of a carboxyl group causes acetic acid to behave as an acid in a chemical reaction, such as being able to react with metallic sodium to form a sodium salt.

Summary: From the structural point of view, the main difference between ethanol, acetaldehyde and acetic acid is the group contained in the molecule: hydroxyl group, aldehyde group and carboxyl group. The presence of such groups directly affects their chemical properties and uses.

2. physical property differences

1. Boiling Point

• Ethanol has a boiling point of 78.3 ° C., a relatively low boiling point, and is easily volatilized.
• Acetaldehyde has a boiling point of 65°C, slightly higher than ethanol.
• Acetic acid has a boiling point of 125.6°C, the highest, and is less volatile.

1. Density

• Ethanol has a density of 0.789g/cm³.
• Acetaldehyde is slightly less dense than ethanol, about 0.684g/cm³.
• Acetic acid has a density of 1.049g/cm³, which is slightly greater than water.

1. Color and smell

• Ethanol is usually a colorless liquid with a faint fragrance.
• Acetaldehyde is also a colorless liquid, but has a pungent sour taste.
• Acetic acid is also colorless, but the smell is more complex, with acidic characteristics.

Summary: Differences in physical properties can help in the initial identification of these three substances. For example, boiling point and density can be used as an aid to quickly distinguish between them.

3. chemical differences

of Reaction of Sodium with
1. All three substances can react with metallic sodium, but the degree of reaction is different:

• Ethanol reacts violently with sodium, producing sodium ethoxide and hydrogen gas.
• Acetaldehyde and sodium reaction is slow, the reaction generates aldehyde sodium and hydrogen.
• Acetic acid reacts most slowly with sodium and usually requires heating to react.

1. Oxidation
   All three substances are oxidizing, but behave differently:

• Ethanol in the oxygen shortage is oxidized to acetaldehyde, completely oxidized to acetic acid.
• Acetaldehyde itself has strong oxidation, can be further oxidized to acetic acid.
• Acetic acid itself cannot be further oxidized.

on the Reaction of Acidic Potassium Permanganate with
1. Three substances were added to the acidic potassium permanganate solution:

• Ethanol will not be oxidized, the solution color has no obvious change.
• Acetaldehyde and potassium permanganate reaction, the solution color from orange to colorless.
• Acetic acid and potassium permanganate reaction, the solution color also from orange red to colorless.

Summary: The difference in chemical reactions is an important basis for identifying these three substances. Through the reaction rate of metallic sodium, oxidation products and high acidity... ', you may need further explanation.