Formaldehyde – Formula, Structure, Uses, and Safety Facts

Formaldehyde is essential in chemistry and helps students understand various practical and theoretical applications related to this topic.

What is Formaldehyde in Chemistry?

A formaldehyde refers to the simplest aldehyde with the chemical formula HCHO. This concept appears in chapters related to organic compounds, aldehydes, and industrial chemistry, making it a foundational part of your chemistry syllabus.

Molecular Formula and Composition

The molecular formula of formaldehyde is CH₂O or HCHO. It consists of one carbon atom, two hydrogen atoms, and one oxygen atom. It is categorized under the aldehyde family of organic compounds and its IUPAC name is methanal.

Preparation and Synthesis Methods

Formaldehyde is mainly produced industrially by the catalytic oxidation of methanol. A common method involves passing methanol vapor mixed with air over a silver or copper catalyst at about 600°C, which forms formaldehyde gas. In the lab, it can also be prepared by heating methanol with potassium dichromate and dilute sulfuric acid. Naturally, small amounts are produced in the atmosphere and in living organisms during metabolism.

Physical Properties of Formaldehyde

Formaldehyde is a colorless gas with a pungent, irritating odor. It is highly soluble in water and usually sold as an aqueous solution called formalin (about 37% formaldehyde by mass). It’s flammable, boils at −19°C, and has a melting point of −92°C. Due to its volatility, it can be detected by smell even at low concentrations.

Chemical Properties and Reactions

Formaldehyde is highly reactive. Its main chemical properties include easy polymerization (to form paraformaldehyde or trioxane), reducing nature (reacts with Tollens' and Fehling's reagents), and participation in condensation reactions such as with ammonia to form hexamethylenetetramine (hexamine). It also reacts with phenol, urea, and melamine to form different synthetic resins. Oxidation of formaldehyde produces formic acid.

Frequent Related Errors

• Confusing formaldehyde (CH₂O) with acetaldehyde (C₂H₄O) or other aldehydes.
• Neglecting formaldehyde’s reactivity during redox and polymerization reactions.
• Using "formalin" and "formaldehyde" interchangeably, though formalin is the aqueous solution.
• Assuming formaldehyde is only artificial; it also occurs naturally in living organisms and the atmosphere.

Uses of Formaldehyde in Real Life

Formaldehyde is widely used in industries and daily life. Some major uses include:

• Production of resins (phenol-formaldehyde, urea-formaldehyde) used in plywood, particle boards, and adhesives.
• Preservation of biological specimens and tissues (in the form of formalin).
• Disinfectant in hospitals and laboratories.
• Manufacture of plastics, paints, explosives, and pharmaceutical products.
• As a starting material to synthesize other chemicals such as hexamine, methanol derivatives, and pentaerythritol.
• Found as a byproduct in small amounts in smoke, car exhaust, and tobacco.

Relation with Other Chemistry Concepts

Formaldehyde is closely related to topics such as Aldehydes and Ketones and Preparation of Aldehydes, helping students build a conceptual bridge between chapters on organic compounds, functional groups, and environmental chemistry.

Step-by-Step Reaction Example

1. Preparation of formaldehyde from methanol

Heat methanol with excess air in the presence of copper or silver catalyst at about 600°C.

CH₃OH + ½ O₂ → HCHO + H₂O

2. The produced formaldehyde gas is cooled and absorbed in water to form formalin.

Final Answer: Formaldehyde is industrially made by methanol oxidation.

Lab or Experimental Tips

Remember formaldehyde by its sharp, irritating odor and use proper safety equipment when handling it in labs. Vedantu educators often explain that formalin (aqueous solution) is commonly used instead of pure formaldehyde gas because it’s easier and safer to handle, especially for biology practicals or chemistry demonstrations.

Try This Yourself

• Write the IUPAC name of HCHO.
• Draw the Lewis structure of formaldehyde.
• Name two products that use formaldehyde-derived resins.
• Explain why formaldehyde is toxic to humans.

Final Wrap-Up

We explored formaldehyde—its structure, properties, reactions, and real-life importance. For more in-depth explanations and exam-prep tips (NEET, JEE, CBSE), explore live classes and notes on Vedantu. Understanding formaldehyde helps you connect key topics in organic chemistry and real-world applications.

• Acetaldehyde
• Hexamine
• Methanol
• Aldehydes and Ketones