PARAFORMALDEHYDE

Paraformaldehyde=Paraform

IUPAC name
benzene;4,5-dibromo-2H-thiophen-2-ide;platinum(2+);2-pyridin-2-ylpyridine

CAS Number
30525-89-4

Molecular Formula
C20H14Br2N2PtS

General description
Paraformaldehyde (PFA) is the smallest polyoxymethylene, the polymerization product of formaldehyde with a typical degree of polymerization of 8–100 units.
Paraformaldehyde commonly has a slight odor of formaldehyde due to decomposition.
Paraformaldehyde is a poly-acetal.
Paraformaldehyde is also referred as polyoxymethylene. It participates as an external CO source in the synthesis of aromatic aldehydes and esters.Paraformaldehyde is a smallest polymerization product of formaldehyde. It possesses the similar features of formaldehyde, which has with a wider range of applications. Paraformaldehyde is extensively used in the manufacturing of synthetic resins like phenolic resins, thiourea, melamine formaldehyde resins, and as a substitute of formalin to generate the resinous binding material. Paraformaldehyde is usually used together with similar chemical compounds like urea, melamine, phenol, resorcinol, tannin or other reactants in the manufacturing of particle board, fibreboard and plywood.

PRODUCTION OF PARAFORMALDEHYDE
Paraformaldehyde is a produced as a white precipitate by condensation from the main species of methanediol in solution of formaldehyde which is also known as formalin. The solution is chiefly of oligomers, but when it becomes large, the material turn into sufficiently insoluble as to precipitate. The reaction is determined to the left, in order to release formaldehyde, by a low concentration of formaldehyde, and quickened by acidic or alkaline conditions. Solid paraformaldehyde has odour of formaldehyde monomer, so it is fundamentally a convenient means of delivering formaldehyde slowly.

Paraformaldehyde may cause skin itching and rash that leads to skin allergy when it is extensively exposed. It has moreover been reported to cause reproductive and mutagenic problems in humans when exposed more.

APPLICATIONS IN CHEMICAL INDUSTRY 
Avast solid form of formaldehyde is an extremely useful reagent in classical organic reactions. Several applications have been discovered in the chemical industry and organic chemistry research laboratories. Paraformaldehyde is used in organic reactions with transition metals as the catalysts. These methodologies, paraformaldehyde has been used as methylene blocks, hydroxymethylation reagents, CO source, syngas surrogate, hydrogen donor or acceptor, formylation and methylation reagents.
As a formaldehyde releasing agent, paraformaldehyde is a potential carcinogen.
Its acute oral median lethal dose in rats is 592 m3D Status
Conformer generation is disallowed since MMFF94s unsupported element, mixture or salt.

Moreover, in recent researches has reported organocatalyzed transformations of paraformaldehyde have been included as well.In some instance paraformaldehyde is depolymerized, the resultant formaldehyde may be make use as a disinfectant, fungicide, and fixative.
Longer chain-length polyoxymethylenes are used as a thermoplastic and are known as polyoxymethylene plastic.

Paraformaldehyde finds diversified usage in chemical industry which can be as both intermediate and a range of fields such as cleaning products, fluorescent lights, organic chemical synthesis, personal care products, and also in consumer goods.

Synthesis
Paraformaldehyde forms slowly in aqueous formaldehyde solutions as a white precipitate, especially if stored in the cold.
Formalin actually contains very little monomeric formaldehyde; most of it forms short chains of polyformaldehyde.
A small amount of methanol is often added as a stabilizer to limit the extent of polymerization.

Reactions
Paraformaldehyde can be depolymerized to formaldehyde gas by dry heating and to formaldehyde solution by water in the presence of a base, an acid or heat.
The high purity formaldehyde solutions obtained in this way are used as a fixative for microscopy and histology.
The resulting formaldehyde gas from dry heating paraformaldehyde is flammable.

Uses
Once paraformaldehyde is depolymerized, the resulting formaldehyde may be used as a fumigant, disinfectant, fungicide, and fixative.
Longer chain-length (high molecular weight) polyoxymethylenes are used as a thermoplastic and are known as polyoxymethylene plastic (POM, Delrin).
It was used in the past in the discredited Sargenti method of root canal treatment.¿

Paraformaldehyde is not a fixative; it must be depolymerized to formaldehyde in solution.
In cell culture, a typical formaldehyde fixing procedure would involve using a 4% formaldehyde solution in phosphate buffered saline (PBS) on ice for 10 minutes.
In histology and pathology specimens preparation, usually, the fixation step is performed using 10% Neutral Buffered Formalin (4% formaldehyde) for, at least, 24 hours.

Paraformaldehyde is also used to crosslink proteins to DNA, as used in ChIP (chromatin immunoprecipitation) which is a technique to determine which part of DNA certain proteins are binding to.

Paraformaldehyde can be used as a substitute of aqueous formaldehyde to produce the resinous binding material, which is commonly used together with melamine, phenol or other reactive agents in the manufacturing of particle board, medium density fiberboard and plywood.

Reactivity Profile
PARAFORMALDEHYDE may react violently with strong oxidizing agents (hydrogen peroxide, performic acid, perchloric acid in the presence of aniline, potassium permanganate, nitromethane).
May react with bases (sodium hydroxide, potassium hydroxide, ammonia), and with nitrogen dioxide (explosive reaction around 180°C).
Reacts with hydrochloric acid to form highly toxic bis(chloromethyl) ether.
Polymerization reaction with phenol may develop sudden destructive pressure.
May generate flammable and/or toxic gases in combination with azo, diazo compounds, dithiocarbamates, nitrides, and strong reducing agents.
Generates toxic formaldehyde gas when heated.
Can react with air to give first peroxo acids, and ultimately formic acid.
These reactions are activated by light, catalyzed by salts of transition metals, and are autocatalytic (catalyzed by the products of the reaction).
Incompatible with liquid oxygen.

Air & Water Reactions
Flammable. Forms aqueous solution of formaldehyde, often quite slowly.

Application Notes
Paraformaldehyde has been used in the past for disinfecting sickrooms, clothing, linen and sickroom utensils.
It has been used as a fumigant and in manufacturing synthetic resins & as a fixative in electron microscopy.
Used in the preparation of formalin fixatives for tissues or cells when the samples are to be used in florescence studies.

Formaldehyde is CH2O, the simplest aldehyde.
Formalin is the name for saturated (37%) formaldehyde solution.
Thus, a protocol calling for 10% formalin is roughly equivalent to 4% formaldehyde.
Beware though, that some solutions have methanol in them to stop polymerization but this could have a negative effect on your sample.
Paraformaldehyde (PFA) is actually polymerized formaldehyde.
"Pure", methanol-free formaldehyde can be made by heating the solid PFA. 
his might be called paraformaldehyde, but it actually isn't because it’s not the polymer form.
You can buy EM grade formaldehyde or you can make your own

Extract
Aldehydes are the most commonly used fixatives.
They serve to stabilize the fine structural details of cells and tissues prior to examination by light or electron microscopy.
Research workers, technicians, pathologists and others who regularly use aldehyde fixatives frequently do not appreciate the nature and properties of these compounds or the reasons for choosing to fix a specimen in formaldehyde, glutaraldehyde or a mixture of the two.
Misconceptions are widespread also about formalin and paraformaldehyde, the commercial products from which formaldehyde-containing solutions are made.

Computed Properties
Chemical formula: OH(CH2O)nH (n = 8 - 100)
Vapour density: 1.03
Specific gravity: 1.40
Flash point: 70 C
Explosion limits: 7.0 - 73%
Appearance: White crystalline solid
Density: 1.42 g·cm−3 (25 °C)
Melting point: 120 °C (248 °F; 393 K)
Solubility in water: Low
Molecular Weight: 669.3
Hydrogen Bond Donor Count: 0
Hydrogen Bond Acceptor Count: 5
Rotatable Bond Count: 1
Exact Mass: 668.88719
Monoisotopic Mass: 666.88924
Topological Polar Surface Area: 51.1Ų
Heavy Atom Count: 26
Formal Charge: 0    
Complexity: 420
Isotope Atom Count: 0
Defined Atom Stereocenter Count: 0
Undefined Atom Stereocenter Count: 0
Defined Bond Stereocenter Count: 0
Undefined Bond Stereocenter Count: 0
Covalently-Bonded Unit Count: 4
Compound Is Canonicalized    : Yes
InChI: 1S/CH2O/c1-2/h1H2
InChIKey: WSFSSNUMVMOOMR-UHFFFAOYSA-N
SMILES: C=O
Canonical SMILES: O=C

The method is applicable to solid paraformaldehyde of aldehyde contents in the range 67 % (m/m) to 97 % (m/m). The principle consists in the reaction of aldehyde present in a test portion with neutralized sodium sulphite solution.
Titration of the liberated sodium hydroxide with sulphuric acid solution using thymolphthalein as indicator. - This document has also been approved by the IUPAC.

Paraformaldehyde possesses the common characteristics with a wide range of applications. Paraformaldehyde is the smallest solid form of liquid formaldehyde, formed by the polymerization of formaldehyde with a typical degree of polymerization of 8-100 units.
As paraformaldehyde is basically a condensed form of formaldehyde, it possesses the common characteristics with a wide range of applications.
Advantages of paraformaldehyde in resin production as compared to aqueous formaldehyde Paraformaldehyde does not need to be dissolved in water in order to take part in a chemical reaction. Higher productivity from existing equipment and less water to be removed from the resin product. Paraformaldehyde made with very low acid content in a chemical resistant environment can prevent the formation of acidic by-products.

Paraformaldehyde generates formaldehyde gas when it is depolymerized by heating.
The depolymerized material reacts with the moisture in the air to form formaldehyde gas.
This process is used for the decontamination of large spaced and laminar-flow biological safety cabinets when maintenance work or filter changes require access to the sealed portion of the cabinet. It is used in the poultry industry as a disinfectant in the hatcheries, and cattle and sheep industry for sanitizing the bedding in the sheds.
It releases formaldehyde gas when the temperatures increase.
It reduces contamination levels caused by moulds, viruses and bacteria.
Agriculture and Pesticides Most paraformaldehyde consumed by the agrochemicals industry is for the herbicides such as bismerthiazol, butachlor, acetochlor, glyphosate, and machete.
Paraformaldehyde, Formadehyde and Formalin Confused?
Formaldehyde is CH2O, the simplest aldehyde.
Formalin is the name for saturated (37%) formaldehyde solution.
Thus, a protocol calling for 10% formalin is roughly equivalent to 4% formaldehyde.
Beware though, that some solutions have methanol in them to stop polymerization but this could have a negative effect on your sample.
Paraformaldehyde (PFA) is actually polymerized formaldehyde.
"Pure", methanol-free formaldehyde can be made by heating the solid PFA.
This might be called paraformaldehyde, but it actually isn`t because it`s not the polymer form. You can buy EM grade formaldehyde or you can make your own.

Paraformaldehyde is a cross-linking fixative used in histology, light and electron microscopy and flow cytometry. It is changed to formaldehyde by heating and by adding small amount of sodium hydroxide.
When the samples are to be used in fluorescence studies, paraformaldehyde is recommended as fixative. In histology it is generally preferred over other fixatives as the others result in more silver grains on the tissues.

A commonly used preservative for starch, xanthan gum, guar gum and other natural polymers that are prone to attack by bacteria.
It is as a trimer of formaldehyde and has the formula O-CH2-O-CH2-O-CH2. Paraformaldehyde is a white, water soluble powder.
When added to a mud in advance of a bacterial inoculation and maintained, paraformaldehyde can effectively control many strains of bacteria.
The amount or paraformaldehyde in a mud can be estimated by oxidizing it with sulfite into formic acid and performing an alkalinity titration, according to a procedure published by API.

Paraformaldehyde is a white, solid polymer of formaldehyde with the pungent, characteristic formaldehyde odor.
Paraformaldehyde is made up of connected formaldehyde molecules.
Paraformaldehyde is slightly soluble in alcohols and insoluble in ethers, hydrocarbons, and carbon tetrachloride.
It is relative insoluble in cold water, but soluble in hot water with depolymerization.
The solubility and rate of solution of paraformaldehyde in water are greatly influenced by pH and temperature.
Both acidic and alkaline pHs and higher temperatures accelerate the rate of solution.
Once dissolved, the paraformaldehyde solution behaves like the methanol-free formaldehyde solution of the same concentration.
Paraformaldehyde is composed of varying molecular weight polymers of polyoxymethylene glycols.
It is generally prepared as 91 or 95% formaldehyde by weight with the remainder being free and combined water.
The combined water is the terminating agent for the paraformaldehyde chains. Paraformaldehyde reacts chemically as formaldehyde at a rate determined by its rate of depolymerization under the conditions of use.
The rate of depolymerization and thus perceived reactivity decreases with increasing molecular weight of the polymer chains.

Paraformaldehyde is widely used by resin manufacturers seeking low water content, or more favorable control of reaction rates when compared to aqueous formaldehyde solutions.
With less dehydration required, paraformaldehyde resins are made in less time.
Better yields result from the complete or partial elimination of dehydration because fewer reactants are lost in the distillate.
Utility costs are reduced because paraformaldehyde requires less steam, cooling water and power for water removal.
The capability of charging more reactants to the process equipment (in the volume otherwise occupied by water and extra azeotroping agent) increases reactor capacity, and reduces capital required for equipment versus the equipment costs and capacity when using aqueous formaldehyde.
Finally, and of increasing importance, less wastewater is produced.
Paraformaldehyde provides a source of formaldehyde for the synthesis of phenol-, urea-, furfural alcohol-, resorcinol- and melamine- formaldehyde resins.
These products find extensive usage in industrial coatings, wood products, textiles, and foundry resins.
Oil well drilling chemicals, lubricating oil additives, adhesive resins, and electrical component molding materials also use Paraformaldehyde.
Miscellaneous end uses include photographic and graphic arts chemicals, pigments, rubber antioxidants, fluorescent tube and ink chemicals, pharmaceuticals, slow release fertilizers and others.

Too many names
There's plenty of confusion regarding this chemical because too many synonyms exist.
Paraformaldyhde is probably still the most common term among biologist, but it ignores attempts to introduce meaningful and systematic names in chemistry.
Polymethanal is clearer: poly - polymer, meth - single carbon, -al - aldehyde group.

Here's a list of equivalent terms: polymethanal, polyoxymethylene, polyformaldehyde, paraformaldehyde, paraform, polytrioxane,.. (regards from Babel) Common abbreviations are PFA, pMeO.

Comparison with methanal
Polymethanal is often preferred over methanal which is also used in fixation of live material.
This is because polymethanal is a solid which makes it easier to transport and a little safer to use. The chemistry of fixation is similar due to the partial depolymerisation of polymethanal in the buffer making process (basic hydrolysis).

Chemistry of fixation
The aldehyde group, especially of methanal, is very reactive. It readily combines with amino groups to amides or with alcohol groups to esters.
These reactions are mostly irreversible. Unreacted molecules have to be removed prior to subsequent experiments since they easily damage proteins like antibodies.

Synonyms
Aldacide    
Ethanol, 2-ethoxy-, polymer with formaldehyde
Flo-Mor
Formaldehyde, polymer with (2-methoxymethylethoxy)propanol    
Formaldehyde, polymer with 1(or 2)-methoxypropanol
Formaldehyde, polymer with 2-ethoxyethanol    
Propanol, (2-methoxymethylethoxy)-, polymer with formaldehyde
Propanol, 1(or 2)-methoxy-, polymer with formaldehyde
UN 2213
Caswell No. 633
EPA Pesticide Chemical Code 043002
Oilstop,
Halowax
Paraformaldehydum
Paraformic aldehyde
Polymerised formaldehyde
Polyoxymethylene glycol
UNII-Y19UC83H8E
TransFix
Granuform
PFA
Granuform 96
WANPFA 92
Granuform M
Granuform 91