Difference Between Paraformaldehyde and Formaldehyde

Main Difference – Paraformaldehyde vs Formaldehyde

Formaldehyde is an aldehyde. It is the simplest aldehyde in the aldehyde series. At room temperature and pressure, it is a gaseous compound. Paraformaldehyde is a white solid with a light pungent odor. It is a polymer formed from formaldehyde. Typically, it is composed of 8-100 formaldehyde units. Paraformaldehyde has chemical and physical properties that are different from formaldehyde. The main difference between paraformaldehyde and formaldehyde is that paraformaldehyde is in the solid phase at room temperature and pressure whereas formaldehyde is a gas.

Key Areas Covered

1. What is Paraformaldehyde
     – Definition, Chemical Properties, Uses
2. What is Formaldehyde
     – Definition, Chemical Properties, Uses
3. What is the Difference Between Paraformaldehyde and Formaldehyde
     – Comparison of Key Differences

Key Terms: Aldehyde, Formaldehyde, Methanal, Paraformaldehyde, Polymerization, Polyoxymethylene, Stabilizer, Trigonal Planar Shape

Difference Between Paraformaldehyde and Formaldehyde - Comparison Summary

What is Paraformaldehyde

Paraformaldehyde is the product obtained from the polymerization of formaldehyde. The IUPAC name of paraformaldehyde is Polyoxymethylene. Paraformaldehyde may have 8-100 formaldehyde units bonded to each other forming a polymer chain. It is a linear polymer of formaldehyde. At room temperature and pressure, it is a white crystalline solid compound.

Paraformaldehyde has a slight odor of formaldehyde due to the decomposition. The general formula of paraformaldehyde is given as OH (CH2O)nH in which “n” ranges from 8 to 100. The melting point of this compound is about 120 °C.

Difference Between Paraformaldehyde and Formaldehyde

Figure 1: Chemical Structure of a Formaldehyde Unit in Paraformaldehyde

Paraformaldehyde is formed in aqueous formaldehyde solutions. But the synthesis is slow. This happens when the solution is kept cool. Usually, methanol is added to formaldehyde solutions as a stabilizer. Without the stabilizer, the solution is unstable and tends to undergo polymerization. First, insoluble macromolecules are formed, which later form paraformaldehyde.

Depolymerization of paraformaldehyde gives formaldehyde gas. Dry heating can be used for depolymerization. A pure formaldehyde solution in water can be obtained in the presence of a base or heat.

Paraformaldehydes with longer polymer chains are used as thermoplastic material. It also participates as an external CO source in the synthesis of aromatic aldehydes and esters. Paraformaldehyde is commercially available as a white powder.

What is Formaldehyde

Formaldehyde is the simplest aldehyde with the chemical formula CH2O. The IUPAC name of formaldehyde is Methanal. The molar mass of formaldehyde is 30 g/mol. At room temperature and pressure, formaldehyde is a colorless gas and has a pungent, irritating odor.

The melting point of formaldehyde is −92 °C, and the boiling point is −19 °C. Formaldehyde contains a carbon atom, two hydrogen atoms and an oxygen atom bonded to each other via covalent chemical bonds. The shape of the molecule is Trigonal planar.

Main Difference - Paraformaldehyde vs Formaldehyde

Figure 2: Chemical Structure of Formaldehyde

Formaldehyde aqueous solution is flammable and corrosive. When preparing the formaldehyde solution, methanol is added to prevent formaldehyde from precipitating as paraformaldehyde. In cold conditions, formaldehyde tends to form a cloudiness in the solution due to the formation of macromolecules via formaldehyde polymerization.

There are many applications of formaldehyde in industries and other areas. It is used as a precursor for many organic synthesis processes; ex: resins such as melamine resin, phenol formaldehyde resin, etc. Apart from that, it is used as a disinfectant. It can kill bacteria and fungi on wood surfaces. However, formaldehyde is toxic and known to be carcinogenic.

Difference Between Paraformaldehyde and Formaldehyde

Definition

Paraformaldehyde: Paraformaldehyde is the product obtained from the polymerization of formaldehyde.

Formaldehyde: Formaldehyde is the simplest aldehyde with the chemical formula CH2O.

Chemical Formula

Paraformaldehyde: The chemical formula of paraformaldehyde is OH(CH2O)nH (where “n” ranges from 8 to 100).

Formaldehyde: The chemical formula of Formaldehyde is CH2O.

Melting Point

Paraformaldehyde: The melting point of paraformaldehyde is about 120 °C.

Formaldehyde: The melting point of Formaldehyde is about −92 °C.

IUPAC Name

Paraformaldehyde: The IUPAC name of paraformaldehyde is Polyoxymethylene.

Formaldehyde: The IUPAC name of formaldehyde is Methanal.

Nature

Paraformaldehyde: Paraformaldehyde is a polymer compound.

Formaldehyde: Formaldehyde is a covalent compound.

Phase of Matter

Paraformaldehyde: Paraformaldehyde is a solid at room temperature and pressure.

Formaldehyde: Formaldehyde is a gas at room temperature and pressure.

Applications

Paraformaldehyde: Paraformaldehyde with longer polymer chains are used as thermoplastic material and participates as an external CO source in the synthesis of aromatic aldehydes and esters.

Formaldehyde: Formaldehyde is used as a precursor for many organic synthesis processes, used as a disinfectant, etc.

Conclusion

Formaldehyde is a monomeric chemical compound. Paraformaldehyde is a polymeric compound. Paraformaldehyde is formed by the polymerization of formaldehyde. The main difference between paraformaldehyde and formaldehyde is that paraformaldehyde is in the solid phase at room temperature and pressure whereas formaldehyde is a gas.

Reference:

1. “Paraformaldehyde 158127.” HO(CH2O)NH, Available here.
2. “Formaldehyde.” National Center for Biotechnology Information. PubChem Compound Database, U.S. National Library of Medicine, Available here.
3. “Paraformaldehyde.” Wikipedia, Wikimedia Foundation, 17 Dec. 2017, Available here.

Image Courtesy:

1. “Paraformaldehyd” By NEUROtiker – Own work (Public Domain) via Commons Wikimedia
2. “Formaldehyde-2D” By Wereon – Own work (Public Domain) via Commons Wikimedia

About the Author: Madhusha

Madhusha is a BSc (Hons) graduate in the field of Biological Sciences and is currently pursuing for her Masters in Industrial and Environmental Chemistry. Her interest areas for writing and research include Biochemistry and Environmental Chemistry.

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