Formaldehyde (CH2O) - Properties, Uses and FAQs

Edited By Team Careers360 | Updated on Jul 02, 2025 04:55 PM IST

Introduction:-
Let us clear up the concept of aldehydes before learning about the formaldehyde formula.
Aldehydes are a class of organic compounds consisting of a carbon doubly bonded to oxygen i.e. carbonyl group at the centre. The carbonyl carbon is attached to hydrogen and an alkyl/aryl/hydrogen atom on either side. The aldehydes can be classified by the presence of the carbonyl group acting as the functional group itself. It is also typically known as the formal group. Click here to get more information about Aldehydes, Ketones and Carboxylic Acids.

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Formaldehyde (CH2O) - Properties, Uses and FAQs

Aldehydes are generally prepared by eliminating a hydrogen atom from alcohol and can be commonly identified as formaldehyde. Now, let us have a look at the formaldehyde formula.

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One of the simplest aldehydes is formaldehyde, also inferred as formalin or methanal. Formaldehyde structural formula is given as follows:-

Methanal or formalin is a flammable and colourless gas with a pungent smell. Methanal or formalin is a generally existing organic compound having a molecular mass of 30.026 g/mL. Formaldehyde structural formula or methanal formula is given as follows:-

Formaldehyde structural formula

Formaldehyde or methanal gas further polymerises to form paraformaldehyde and so it is conserved as an aqueous solution. We all know that the formaldehyde chemical formula is CH₂O. The bond between carbon and oxygen in the carbonyl functional group is polar, making the compound highly reactive. The oxygen atom of the carbonyl group is capable of attracting electrons more strongly than the carbon atom. This creates a partial negative charge and a partial positive charge at both the ends of the functional group. This causes it to stick to the polar particles and empowers it with some ability to attract and donate electrons.

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Some properties of formaldehyde are listed below:-

Formation of salt formats and ethanol on reacting with a strong base like NaOH.

The chemical equation is represented below-

2HCHO + NaOH →HCOONa + CH₃OH

Formaldehyde forms formidable and water in reacting with ammonia, and the reaction is given below-

6HCHO + 4NH₃ → (CH₂)₆N₄+ 6H₂O

Now let us study the preparation techniques of methanal or formaldehyde:-

Lab method:

A blend of methanol vapours and the air is passed over platinumised asbestos or silver or copper catalyst at 300°C.

Industrial method:

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A blend of methanol vapours and the air is passed over iron oxide – molybdenum oxide at 500°C.

Methanal structural formula:-

Methanal structure and methanal formula is same as formaldehyde i.e. CH₂O.

Methanal is nothing but a 37% (w/w) aqueous solution, furthermore known as formalin. It usually consists of methyl alcohol and an inhibitor which is usually an ethyl (vinyl) polymer to prevent it from further polymerization. The most important use of methanal is in the manufacture of methanal resins. Methanal is mostly produced by a process that involves both dehydrogenation and oxidation.

August von Hofmann discovered methanal in 1867. The majority of methanal exist as formalin and is used in the production of dyes and plastic material.

In the early days, chemical compounds were frequently named on the subject of how they have been derived, or maybe, where they have been derived. Even the factors maintain the historical terminology of their symbols, like Fe (Ferro) for iron and Hg (mercury). As this case illustrates, we've systematized the preceding useful organization designations (aldehydes are represented with the aid of using the suffix-“al” in preference to the complete word).

As an increasing number of new compounds (and factors) have been located or made, a consistent nomenclature system has become more important to transfer knowledge in the textual aspect. Hence, IUPAC (International Union of Pure and Applied Chemistry) was established to construct nomenclature rules.

So, the word formaldehyde was derived from formic acid.

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Formalin:-

Formalin chemical formula is CH₂O; same as formaldehyde formula. Formalin is usually used as a reducing agent for producing formic acid as it has a neutral pH. It also has its application as herbicides and disinfectants. It is so used because it inactivates viruses and toxins when used in a vaccine. Further, it is used in cosmetic products.

This aqueous solution of formaldehyde or methanal is termed formalin. Formalin formula is the same as formaldehyde i.e CH₂O.

Formalin

Formalin is nothing but formaldehyde/methanal dissolved in water. A 37% aqueous solution of methanal is usually used as formalin for various purposes.

People often get confused with formaldehyde and formalin, but forget about a basic difference between these two. Formaldehyde is a colourless gas while formalin is an aqueous solution of formaldehyde.

Let us have a look at the role of formaldehyde in human beings:

Formaldehyde plays an important role in the cellular metabolism of humans and mammals. A human can die after ingesting 30 ml of 37% of formaldehyde solution. Formaldehyde irritates the eyes when exposed to concentrations above 0.1 ppm. Inhaling this much amount of formaldehyde results in headaches, burning sensation, breathing problems and is fatal for asthmatic patients.

Uses of formaldehyde:-

It is applied withinside the manufacture of resins like urea-formaldehyde and plastics along with bakelite.
It is employed in the production of dyes – indigo, pararosaniline, etc.
Also applied as a decolourising agent in barrel dyeing.
Used in the production of urinary antibacterial which is urotropine.
Used to process the polio vaccine.

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Frequently Asked Questions (FAQs)

1. What is the key difference between formaldehyde and formalin?

Formaldehyde exists as a gas and formalin is an aqueous solution containing formaldehyde.

2. Does exposure to formaldehyde cause cancer?

Exposure to relatively greater concentrations of formaldehyde can cause cancer according to laboratory tests conducted on lab animals.

3. What is formaldehyde a problem?

Some populations may experience health issues when exposed to a concentration greater than 0.1 parts per million. They are listed below-

Watery eyes.

Burning sensations in eyes, mouth, throat

Coughing

Wheezing

Nausea

Irritation to skin.

4. What are the various forms of formaldehyde?

Formaldehyde encompasses various forms which are interconvertible. They are-

Molecular formaldehyde – It is a colourless gas having a pungent odour.
1,3,5 Trioxane – It is a trimer of formaldehyde having molecular formula (CH₂O)₃. It exists as a white solid dissolving without getting degraded in organic solvents.
Paraformaldehyde – Formaldehyde gets converted to paraformaldehyde on polymerization. Again it resists as a white solid which is mostly insoluble in all solvents. The formula for paraformaldehyde is HO(CH₂O)_nH.

5. Why formaldehyde is highly reactive?

Formaldehyde which is a member of aldehydes, is highly reactive due to its strong electrophilic properties. It is a colorless, pungent , low molecular weight. It is poisonous gas which rapidly passes into gaseous phase at room temperature, can burn, and can dissolve very well in water.

6. What is the main function of formalin?

Formalin is used as a preservative. It is specially used to preserve biological specimens in zoological and medical laboratories. Formalin solution helps the specimens to stay as it is for a longer duration delaying the decaying process.

7. How does formaldehyde impact human skin?

Exposure to a certain amount of formaldehyde irritates the eyes and burning sensations in the mouth.

8. Why formaldehyde is soluble in water?

Formaldehyde is not an ionic compound but it is a polar compound. When it is mixed with water, it is solvated by water molecules (i.e. surrounded) by hydrogen bonding interaction, hence it is soluble in water.

9. How does the structure of formaldehyde contribute to its reactivity?

The carbonyl group (C=O) in formaldehyde makes it highly reactive. The carbon atom is electrophilic due to the electronegative oxygen, while the oxygen can act as a nucleophile. This dual nature allows formaldehyde to participate in various addition and condensation reactions.

10. What is the difference between formaldehyde and methanal?

Formaldehyde and methanal are the same compound. Methanal is the IUPAC name for formaldehyde, derived from methane (the simplest alkane) with the -al suffix indicating an aldehyde. Formaldehyde is the more common trivial name used in everyday chemistry and industry.

11. How does the polarity of formaldehyde affect its properties?

The carbonyl group in formaldehyde creates a significant dipole moment, making the molecule polar. This polarity contributes to its high solubility in water, its ability to form hydrogen bonds, and its relatively high boiling point compared to molecules of similar molecular weight.

12. How does formaldehyde affect proteins in biological systems?

Formaldehyde can react with various functional groups in proteins, particularly amino groups, forming cross-links between proteins. This process, known as protein fixation, can alter the structure and function of proteins, which is why formaldehyde is used in tissue preservation but can also be harmful to living organisms.

13. What is the mechanism of formaldehyde's toxicity?

Formaldehyde's toxicity primarily stems from its ability to react with and modify proteins and DNA. It can form cross-links between proteins and DNA, disrupting cellular functions. Additionally, it can irritate mucous membranes and potentially act as a carcinogen through prolonged exposure.

14. Why is formaldehyde a gas at room temperature while other aldehydes are liquids?

Formaldehyde is a gas at room temperature due to its small molecular size and weak intermolecular forces. Unlike larger aldehydes, it lacks the additional carbon chains that would increase Van der Waals forces and raise the boiling point.

15. How does formaldehyde differ from other aldehydes in terms of oxidation?

Formaldehyde is unique among aldehydes as it can be oxidized to formic acid (HCOOH) but cannot undergo further oxidation. Other aldehydes can be oxidized to carboxylic acids with longer carbon chains.

16. What is the Tollens' test, and how does it apply to formaldehyde?

The Tollens' test is used to distinguish aldehydes from ketones. Formaldehyde, being an aldehyde, will produce a silver mirror when reacted with Tollens' reagent (silver nitrate in ammonia solution) due to its ability to be oxidized.

17. What is the difference between formaldehyde and paraformaldehyde?

Paraformaldehyde is a polymer of formaldehyde. While formaldehyde is a gas at room temperature, paraformaldehyde is a solid white powder. Paraformaldehyde slowly releases formaldehyde when heated or in solution, making it a convenient way to store and transport formaldehyde.

18. How does formaldehyde participate in the Cannizzaro reaction?

The Cannizzaro reaction is a unique redox reaction that formaldehyde undergoes in the presence of strong bases. In this reaction, one molecule of formaldehyde is oxidized to formic acid while another is reduced to methanol, demonstrating formaldehyde's ability to act as both an oxidizing and reducing agent.

19. What is formalin, and how does it relate to formaldehyde?

Formalin is an aqueous solution containing 37-40% formaldehyde with a small amount of methanol as a stabilizer. It's the common form in which formaldehyde is stored and used, particularly for preservation and disinfection purposes.

20. Why is formaldehyde used as a preservative?

Formaldehyde is an effective preservative because it can cross-link proteins, preventing their decomposition. This property makes it useful for preserving biological specimens and in the embalming process.

21. How does formaldehyde contribute to indoor air pollution?

Formaldehyde can be released from various household products and building materials, such as pressed wood products and certain fabrics. Its volatility allows it to easily enter the air, potentially causing respiratory irritation and other health issues.

22. What is the role of formaldehyde in the production of plastics?

Formaldehyde is a key component in the production of various plastics, particularly formaldehyde-based resins like urea-formaldehyde and phenol-formaldehyde resins. These resins are used in the manufacture of plywood, particleboard, and other composite wood products.

23. What is formaldehyde and why is it important in chemistry?

Formaldehyde (CH2O) is the simplest aldehyde, consisting of a carbonyl group (C=O) bonded to two hydrogen atoms. It's important in chemistry due to its widespread use in industry, its role in biological processes, and its status as a model compound for understanding aldehyde reactions.

24. What is the mechanism of formaldehyde's reaction in the Prins reaction?

In the Prins reaction, formaldehyde reacts with an alkene in the presence of an acid catalyst. The mechanism involves the protonation of formaldehyde, followed by electrophilic addition to the alkene. This reaction is important in organic synthesis for creating new carbon-carbon bonds.

25. How is formaldehyde produced industrially?

Industrially, formaldehyde is primarily produced through the catalytic oxidation of methanol. This process, known as the FORMOX process, uses a silver or metal oxide catalyst to convert methanol and oxygen into formaldehyde and water.

26. What is the importance of formaldehyde in the synthesis of other organic compounds?

Formaldehyde is a versatile building block in organic synthesis. It can participate in various reactions like aldol condensations, Mannich reactions, and reductive aminations, leading to the formation of more complex organic molecules used in pharmaceuticals, dyes, and other industrial products.

27. What is formose reaction, and why is it significant?

The formose reaction is a complex series of reactions where formaldehyde polymerizes to form various sugars in the presence of alkaline catalysts. This reaction is significant in prebiotic chemistry theories, suggesting a possible route for the formation of complex carbohydrates in early Earth conditions.

28. How does formaldehyde interact with DNA, and what are the implications?

Formaldehyde can react with DNA, forming cross-links between DNA and proteins or between DNA strands. This property is utilized in some molecular biology techniques for fixing genetic material. However, it also underlies formaldehyde's potential mutagenic and carcinogenic effects.

29. How does formaldehyde contribute to the "new car smell"?

The "new car smell" is partly due to the off-gassing of formaldehyde from various car components. Formaldehyde is used in the production of many car interior materials, including adhesives, plastics, and fabrics. As these materials slowly release formaldehyde, it contributes to the characteristic odor.

30. What is the role of formaldehyde in the production of mirrors?

Formaldehyde is used in the production of mirrors as a reducing agent in the silvering process. When mixed with silver nitrate and ammonia (Tollens' reagent), formaldehyde reduces silver ions to metallic silver, which deposits on the glass surface to create the reflective layer.

31. How does formaldehyde behave in aqueous solution?

In aqueous solution, formaldehyde exists primarily as its hydrate, methylene glycol (CH2(OH)2). This hydration is reversible, with an equilibrium strongly favoring the hydrate form. This behavior affects its reactivity and properties in water-based environments.

32. What is the significance of formaldehyde in the Strecker synthesis?

In the Strecker synthesis, formaldehyde is used to produce glycine, the simplest amino acid. This reaction involves the condensation of formaldehyde with ammonia and hydrogen cyanide, followed by hydrolysis. It demonstrates formaldehyde's role in the synthesis of biologically important molecules.

33. How does formaldehyde compare to acetaldehyde in terms of reactivity?

Formaldehyde is generally more reactive than acetaldehyde due to less steric hindrance around the carbonyl group. The absence of an alkyl group adjacent to the carbonyl in formaldehyde makes it more accessible to nucleophiles, enhancing its reactivity in many reactions.

34. What is the environmental impact of formaldehyde emissions?

Formaldehyde emissions can contribute to air pollution and the formation of ground-level ozone. It can also react with other air pollutants to form secondary organic aerosols, which are a component of smog. In aquatic environments, formaldehyde can be harmful to organisms but typically breaks down rapidly.

35. How is formaldehyde detected and measured in air or materials?

Formaldehyde can be detected using various methods, including colorimetric tests, chromatographic techniques (like HPLC or GC-MS), and specialized formaldehyde meters. For air quality testing, passive samplers or active air sampling devices are often used, followed by laboratory analysis.

36. What is the role of formaldehyde in the human body?

Formaldehyde is naturally produced in small amounts in the human body as part of normal metabolic processes. It plays a role in the one-carbon pool, which is important for various biosynthetic pathways. However, the body rapidly metabolizes formaldehyde to prevent accumulation.

37. How does formaldehyde contribute to the production of textiles?

Formaldehyde is used in the textile industry to produce wrinkle-resistant and easy-care fabrics. It's a key component in resins that are applied to fabrics to create cross-links between cellulose molecules, improving the fabric's resistance to wrinkling and shrinking.

38. How does formaldehyde's structure contribute to its ability to form polymers?

Formaldehyde's small size and high reactivity make it an excellent monomer for polymerization. Its carbonyl group can react with various compounds, forming new carbon-carbon or carbon-heteroatom bonds. This allows for the formation of diverse polymers like polyoxymethylene and phenol-formaldehyde resins.

39. What is the relationship between formaldehyde and methanol in terms of oxidation states?

Formaldehyde represents an intermediate oxidation state between methanol and formic acid. Methanol can be oxidized to formaldehyde, which can be further oxidized to formic acid. This sequence demonstrates the progressive increase in the oxidation state of the carbon atom.

40. How does formaldehyde interact with amino acids, and what are the implications for protein structure?

Formaldehyde can react with the amino groups of amino acids, forming methylene bridges. In proteins, this can lead to cross-linking between different amino acid residues or between different protein molecules. This process can significantly alter protein structure and function, which is the basis for its use in tissue fixation.

41. What is the significance of formaldehyde in the production of vaccines?

Formaldehyde is used in vaccine production to inactivate viruses or bacterial toxins. It modifies proteins in these pathogens, rendering them harmless while still allowing them to stimulate an immune response. The formaldehyde is then removed or reduced to negligible levels in the final vaccine product.

42. How does the presence of formaldehyde affect indoor air quality?

Formaldehyde can negatively impact indoor air quality by causing respiratory irritation, headaches, and other health issues. It's often released from building materials, furniture, and household products. Proper ventilation and use of low-emission materials are important for maintaining good indoor air quality.

43. What is the role of formaldehyde in the synthesis of methylenedioxy compounds?

Formaldehyde is a key reagent in the synthesis of methylenedioxy compounds, which are important in the production of certain pharmaceuticals and fragrances. It reacts with catechols (1,2-dihydroxybenzenes) to form the methylenedioxy bridge, a characteristic structural feature in these compounds.

44. How does formaldehyde participate in the Eschweiler-Clarke reaction?

In the Eschweiler-Clarke reaction, formaldehyde is used to methylate primary or secondary amines. The reaction involves the condensation of the amine with formaldehyde, followed by reduction, typically using formic acid. This reaction is valuable for selectively introducing methyl groups to amines.

45. What is the significance of formaldehyde in the production of melamine resins?

Formaldehyde is a crucial component in the production of melamine resins. It reacts with melamine to form a thermosetting plastic with excellent heat resistance and hardness. These resins are widely used in laminates, kitchenware, and other applications requiring durable, heat-resistant materials.

46. How does formaldehyde's reactivity compare to that of other carbonyl compounds?

Formaldehyde is generally more reactive than other carbonyl compounds like higher aldehydes or ketones. This enhanced reactivity is due to its small size, lack of steric hindrance, and the absence of electron-donating groups that could stabilize the carbonyl. This makes formaldehyde particularly prone to nucleophilic addition reactions.

47. What is the role of formaldehyde in the synthesis of acetal polymers?

Formaldehyde is the key monomer in the production of acetal polymers, such as polyoxymethylene (POM). These polymers are formed through the polymerization of formaldehyde or its cyclic trimer, trioxane. Acetal polymers are known for their high strength, stiffness, and resistance to wear and chemicals.

48. How does formaldehyde contribute to the Leuckart reaction?

In the Leuckart reaction, formaldehyde is used along with formic acid to convert ketones or aldehydes into formamides. This reaction is valuable in organic synthesis for the production of various nitrogen-containing compounds, including pharmaceuticals and agrochemicals.

49. What is the significance of formaldehyde in the production of bakelite?

Formaldehyde is a crucial component in the production of bakelite, one of the first synthetic plastics. It reacts with phenol in the presence of a catalyst to form a thermosetting resin. Bakelite's heat resistance and electrical insulation properties made it revolutionary in the early 20th century.

50. How does formaldehyde interact with sulfur-containing compounds?

Formaldehyde can react with various sulfur-containing compounds. For example, it reacts with hydrogen sulfide to form trithiane, a cyclic trimer. With thiols, it can form thiazolidines. These reactions are important in organic synthesis and have implications in biological systems where sulfur-containing amino acids are present.

51. What is the role of formaldehyde in the production of hexamine?

Formaldehyde reacts with ammonia to produce hexamine (hexamethylenetetramine), a compound used in the production of plastics, pharmaceuticals, and explosives. This reaction demonstrates formaldehyde's ability to form complex, nitrogen-containing structures through condensation reactions.

52. How does formaldehyde contribute to the formation of atmospheric aerosols?

Formaldehyde can participate in photochemical reactions in the atmosphere, contributing to the formation of secondary organic aerosols. These reactions, often involving other volatile organic compounds and nitrogen oxides, play a role in the formation of smog and can impact air quality and climate.

53. What is the significance of formaldehyde in the synthesis of methylal?

Formaldehyde reacts with methanol in the presence of an acid catalyst to form methylal (dimethoxymethane). This compound is used as a solvent and fuel additive. The reaction demonstrates formaldehyde's ability to form acetals, a characteristic reaction of aldehydes.

54. How does formaldehyde behave in Grignard reactions?

Formaldehyde reacts with Grignard reagents to form primary alcohols. This reaction is unique among aldehydes as it always results in a primary alcohol, regardless of the Grignard reagent used. It's a valuable method for extending carbon chains by one carbon atom in organic synthesis.

55. What is the role of formaldehyde in the production of 1,4-butanediol?

Formaldehyde is used in the production of 1,4-butanediol through the Reppe process. It reacts with acetylene in a series of steps to form the diol. This process demonstrates formaldehyde's importance in