Formaldehyde (CH₂O) — Properties, Uses & Safety

Overview

Formaldehyde (HCHO), systematically named methanal, is the simplest aldehyde and one of the most important industrial chemicals. With a molar mass of 30.03 g/mol, formaldehyde is a colorless gas at room temperature with a strong, pungent, suffocating odor. It is highly reactive due to its aldehyde functional group — a carbonyl group (C=O) bonded to a hydrogen atom — which makes it susceptible to nucleophilic addition reactions. Formaldehyde is commonly encountered in aqueous solution as formalin (typically 37% formaldehyde by weight), which has been used for over a century as a biological preservative and embalming fluid. Industrially, formaldehyde is produced by the catalytic oxidation of methanol (2 CH3OH + O2 → 2 HCHO + 2 H2O) using silver or iron-molybdenum oxide catalysts. Global production exceeds 50 million tons per year. The largest use of formaldehyde is in the production of resins and adhesives — urea-formaldehyde, phenol-formaldehyde (Bakelite), and melamine-formaldehyde resins are used in plywood, particleboard, insulation, and laminates. Other uses include textile finishing (wrinkle-resistant fabrics), production of the disinfectant glutaraldehyde, manufacture of the plastic polyoxymethylene (Delrin), and as a precursor to various pharmaceuticals and agricultural chemicals. Formaldehyde is also produced naturally in small amounts by the human body as part of normal metabolism and is present in fruits, vegetables, and combustion products (including cigarette smoke and vehicle exhaust). Safety is a critical concern with formaldehyde. It is classified as a Group 1 carcinogen by the International Agency for Research on Cancer (IARC), with chronic exposure linked to nasopharyngeal cancer and leukemia. It is also a potent irritant to the eyes, skin, and respiratory tract, and a common cause of contact dermatitis. GHS pictograms include the skull and crossbones, health hazard, corrosion, and flame symbols. For chemistry students, formaldehyde is valuable for learning about the aldehyde functional group, nucleophilic addition reactions (including the formation of hemiacetals and acetals), condensation polymerization (formaldehyde resins), oxidation of alcohols to aldehydes, and the Tollens and Fehling tests for aldehydes. Its role in everyday materials from furniture to clothing connects organic chemistry to real-world applications and safety awareness.

IUPAC Name

methanal

CAS Number

50-00-0

PubChem CID

712

Molecular Formula

CH₂O

Molar Mass

30.026 g/mol

State at STP

gas

Appearance

Colorless gas with pungent odor (aqueous solution is formalin)