Paraformaldehyde
3209372
214736674
2008-05-25T01:19:38Z
Cacycle
83784
Synthesis, used as
{{Chembox new
| ImageFile = Paraformaldehyd.svg
| ImageSize = 150px
| IUPACName = Polyoxymethylene
| OtherNames =
| Section1 = {{Chembox Identifiers
| CASNo = 30525-89-4
| PubChem = 24898648
| SMILES = }}
| Section2 = {{Chembox Properties
| Formula = (CH<sub>2</sub>O)<sub>n</sub> (n = 8 - 100)
| MolarMass =
| Appearance = white crystalline solid
| Density = 0.88 g·cm<sup>−3</sup> (20 ºC)
| MeltingPt = 120-170 °C
| BoilingPt =
| Solubility = low}}
| Section3 = {{Chembox Hazards
| EUClass = Toxic (T); Corrosive (C)
| ExternalMSDS = [http://msds.chem.ox.ac.uk/PA/paraformaldehyde.html Oxford MSDS]
| FlashPt =
| Autoignition = }}
}}
'''Paraformaldehyde''', also known as '''polyoxymethylene''', is the [[condensation]] product of [[formaldehyde]] with a typical chain length of 8 - 100 units. Long chain-length (high molecular weight) paraformaldehyde is used as a [[thermoplastic]] and is known known as [[polyoxymethylene plastic]] (POM, ''Delrin'', polyformaldehyde). Paraformaldehyde commonly has a slight odor of formaldehyde due to decomposition. Paraformaldehyde is a poly-[[acetal]]. Paraformaldehyde is used as [[fumigant]], [[disinfectant]], and [[fungicide]], and for the preparation of pure formaldehyde.
== Synthesis ==
Paraformaldehyde forms slowly in [[formaldehyde]] solutions (formaline) as a white precipitate, especially if stored in the cold. Formaline actually contains very little monomeric formaldehyde most of it forms short chains of polyformaldehyde. A few percent of [[methanol]] is often added as a [[stabilizer]] to limit the extent of [[polymerization]].
== Reactions ==
Paraformaldehyde can be [[depolymerization|depolymerized]] to formaldehyde gas by dry heating and to formaldehyde solution by [[water (molecule)|water]] in the presence of [[acid]] or heat. The very pure formaldehyde solutions obtained in this way are used as a [[fixation (histology)|fixative]] for [[microscopy]] and [[histology]].
Paraformaldehyde is flammable as it decomposes in the heat into the flammable gas formaldehyde.
== Toxicity ==
As a formaldehyde releasing agent, paraformaldehyde is a suspected carcinogen. Its acute oral [[LD50|LD<sub>50</sub>]] in rats is 592 mg/kg.
== See also ==
* [[Polyoxymethylene plastic]]
* [[1,3,5-Trioxane]], the cyclic trimer of formaldehyde
* [[Polymer]]
== References ==
<references/>
[[Category:Polyethers]]
[[Category:Acetals]]
[[cs:Paraformaldehyd]]
[[de:Paraformaldehyd]]
[[ca:Poliacetal]]
[[en:Polyoxymethylene]]
[[es:Poliacetal]]
[[it:Paraformaldeide]]
[[pl:Polioksymetylen]]
[[pt:Poliacetal]]
[[ru:Полиформальдегид]]
[[uk:Поліформальдегід]]