Formaldehyde (/fɔːrˈmældɪhaɪd/ (listen) for-MAL-di-hide, US also /fər-/ (listen) fər-) (systematic name methanal) is a naturally occurring organic compound with the formula CH₂O and structure H−CHO. The pure compound is a pungent, colourless gas that polymerises spontaneously into paraformaldehyde (refer to section Forms below), hence it is stored as an aqueous solution (formalin), which is also used to store animal specimens. It is the simplest of the aldehydes (R−CHO). The common name of this substance comes from its similarity and relation to formic acid.

Formaldehyde

Names
Preferred IUPAC name Formaldehyde
Systematic IUPAC name Methanal
Other names Methyl aldehyde Methylene glycol (diol forms in aqueous solution) Methylene oxide Formalin (aqueous solution) Formol Carbonyl hydride
Identifiers
CAS Number	50-00-0 Y
3D model (JSmol)	Interactive image
3DMet	B00018
Beilstein Reference	1209228
ChEBI	CHEBI:16842 Y
ChEMBL	ChEMBL1255 Y
ChemSpider	692 Y
DrugBank	DB03843 Y
ECHA InfoCard	100.000.002
EC Number	200-001-8
E number	E240 (preservatives)
Gmelin Reference	445
IUPHAR/BPS	4196
KEGG	D00017 Y
MeSH	Formaldehyde
PubChem CID	712
RTECS number	LP8925000
UNII	1HG84L3525 Y
UN number	2209
CompTox Dashboard (EPA)	DTXSID7020637
InChI InChI=1S/CH2O/c1-2/h1H2 Y Key: WSFSSNUMVMOOMR-UHFFFAOYSA-N Y InChI=1/CH2O/c1-2/h1H2 Key: WSFSSNUMVMOOMR-UHFFFAOYAT
SMILES C=O
Properties
Chemical formula	CH2O
Molar mass	30.026 g·mol−1
Appearance	Colorless gas
Density	0.8153 g/cm3 (−20 °C) (liquid)
Melting point	−92 °C (−134 °F; 181 K)
Boiling point	−19 °C (−2 °F; 254 K)
Solubility in water	400 g/L
log P	0.350
Vapor pressure	> 1 atm
Acidity (pKa)	13.27 (hydrate)
Magnetic susceptibility (χ)	−18.6·10−6 cm3/mol
Dipole moment	2.330 D
Structure
Point group	C2v
Molecular shape	Trigonal planar
Thermochemistry
Heat capacity (C)	35.387 J·mol−1·K−1
Std molar entropy (S⦵298)	218.760 J·mol−1·K−1
Std enthalpy of formation (ΔfH⦵298)	−108.700 kJ·mol−1
Gibbs free energy (ΔfG⦵)	−102.667 kJ·mol−1
Std enthalpy of combustion (ΔcH⦵298)	571 kJ·mol−1
Pharmacology
ATCvet code	QP53AX19 (WHO)
Hazards
GHS labelling:
Pictograms
Signal word	Danger
Hazard statements	H301, H311, H314, H317, H331, H335, H341, H350, H370
Precautionary statements	P201, P280, P303+P361+P353, P304+P340+P310, P305+P351+P338, P308+P310
NFPA 704 (fire diamond)	3 4 0 COR
Flash point	64 °C (147 °F; 337 K)
Autoignition temperature	430 °C (806 °F; 703 K)
Explosive limits	7–73%
Lethal dose or concentration (LD, LC):
LD50 (median dose)	100 mg/kg (oral, rat)
LC50 (median concentration)	333 ppm (mouse, 2 h) 815 ppm (rat, 30 min)
LCLo (lowest published)	333 ppm (cat, 2 h)
NIOSH (US health exposure limits):
PEL (Permissible)	TWA 0.75 ppm ST 2 ppm (as formaldehyde and formalin)
REL (Recommended)	Ca TWA 0.016 ppm C 0.1 ppm [15-minute]
IDLH (Immediate danger)	Ca [20 ppm]
Safety data sheet (SDS)	MSDS(Archived)
Related compounds
Related aldehydes	Acetaldehyde Butyraldehyde Decanal Heptanal Hexanal Nonanal Octadecanal Octanal Pentanal Propionaldehyde
Related compounds	Methanol Formic acid
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). Y verify (what is YN ?) Infobox references

Formaldehyde is an important precursor to many other materials and chemical compounds. In 1996, the installed capacity for the production of formaldehyde was estimated at 8.7 million tons per year. It is mainly used in the production of industrial resins, e.g., for particle board and coatings.