Home > Formaldehyde
 | | | |
Learn more about "Formaldehyde"
|
|
|
Formaldehyde{{Chembox new
| Name = Formaldehyde ( methanal)
| ImageFile = Formaldehyde-2D.svg
| ImageSize = 120px
| ImageFileL1 = Formaldehyde-3D-balls-A.png
| ImageSizeL1 = 120px
| ImageFileR1 = Formaldehyde-3D-vdW.png
| ImageSizeR1 = 120px
| IUPACName= Methanal
| OtherNames = formol, methyl aldehyde, methylene oxide| Section1 =
| Section2 =
| Section3 =
| Section7 =
| Section8 =
}}
Formaldehyde (IUPAC name '''methanal''') is a chemical compound with the chemical formula|formula H2CO. It is the simplest aldehyde. Formaldehyde exists in several forms aside from H2CO: the cyclic trimer trioxane and the polymer Polyoxymethylene|paraformaldehyde. It exists in water as the hydrate H2C(OH)2. Aqueous solutions of formaldehyde are referred to as '''formalin'''. "100%" formalin consists of a saturated solution of formaldehyde (roughly 40% by mass) in water, with a small amount of stabilizer (chemistry)|stabilizer, usually methanol to limit oxidation and polymerization. It is produced on a substantial scale of 6M tons/y. In view of its widespread use, toxicity, and volatility, exposure to formaldehyde is significant consideration for human health.[G. Reuss, W. Disteldorf, A. O. Gamer, A. Hilt, “Formaldehyde” in Ullmann’s Encyclopedia of Industrial Chemistry Wiley-VCH, 2005, Weinheim.]
Occurrence
Formaldehyde is an intermediate in the oxidation (or combustion) of methane as well as other carbon compounds, e.g. forest fires, in automobile exhaust, and in tobacco smoke. When produced in the Earth's atmosphere|atmosphere by the action of sunlight and oxygen on atmospheric methane and other hydrocarbons, it becomes part of smog.
Biological occurrence
Formaldehyde, as well as its oligomers and hydrates are rarely encountered in living organisms. Methanogenesis proceeds via the equivalent of formaldehyde, but this one-carbon species is masked as a methylene group in methanopterin. Formaldehyde is the primary cause of methanol's toxicity, since methanol is metabolised into toxic formaldehyde by alcohol dehydrogenase. Formaldehyde is converted to formic acid in the body.
Interstellar formaldehyde
Initial Discovery
Formaldehyde was first discovered in interstellar space in 1969 by L. Snyder ''et al.''. using the National Radio Astronomy Observatory. H2CO was detected by means of the 111 - 110 ground state rotational transition at 4830 MHz [Snyder, L. E., Buhl, D., Zuckerman, B., & Palmer, P. 1969, ''Phys. Rev. Lett.'', 22, 679].
Subsequent detections
Formaldehyde was the first polyatomic Organic chemistry|organic molecule detected in the interstellar medium[Zuckerman, B.; Buhl, D.; Palmer, P.; Snyder, L. E. 1970, ''Astrophysical Journal'', 160, 485] and since its initial detection has been observed in many regions of the Milky Way galaxy|galaxy. The isotopic ratio of 12C/13C was determined to be about or less than 50% in the galactic disk [Henkel, C.; Guesten, R.; Gardner, F. F. 1985, ''Astronomy and Astrophysics'', 143, 148]. Formaldehyde has been used to map out kinematic features of dense clouds located near Gould's Belt of local bright stars [Sandqvist, A.; Tomboulides, H.; Lindblad, P. O. 1988, ''Astronomy and Astrophysics'', 205, 225]. In 2007, the first H2CO 6 cm maser flare was detected[Araya, E. _et al_. 2007, ''Astrophysical Journal'', 654, L95]. It was a short duration outburst in IRAS 18566 + 0408 that produced a line profile consistent with the superposition of two Gaussian components, which leads to the belief that an event outside the maser gas triggered simultaneous flares at two different locations[Hoffman, I. M.; Goss, W. M.; Palmer, P. 2007, ''Astrophysical Journal'', 654, 971]. According to Araya ''et al.''., H2CO are different from other masers in that they are weaker than most other masers (such as OH, CH3OH, and H2O) and have only been detected near very young massive stellar objects [Araya ''et al''. 2007, ''Astrophysical Journal'', 669, 1050]. Unlike OH, H2O, and CH3OH, only five galactic star forming regions have associated formaldehyde maser emission, which has only been observed through the 110 → 111 transition[J. G. Mangum ''et al''. 2008, ''Astrophysical Journal'', 673, 832.].
Interstellar reactions
The gas-phase reaction that produces formaldehyde possesses modest barriers and is too inefficient to produce the abundance of formaldehyde that has been observed[Woon, D.E. 2002, ''Astrophysical Journal'', 569, 541.]. One proposed mechanism for the formation is the hydrogenation of CO ice, shown below
- H + CO --> HCO + H --> H2CO (rate constant=9.2*10-3 s-1)
This is the basic production mechanism leading to H2CO; there are several side reactions that take place with each step of the reaction that are based on the nature of the ice on the grain according to David Woon[Awad ''et al''. 2005, ''Astrophysical Journal'', 626, 262.]. Awad ''et al.''. mention that this is a surface level reaction only and only the monolayer is considered in calculations; this includes the surface within cracks in the ice[W. A. Schutte ''et al''. 1993, ''Science'', 259, 1143.],[W. A. Schutte ''et al''. 1993, ''Icarus'', 104, 118.]. Reactions involving formaldehyde have been observed to produce molecules containing C-H, C-O, O-H, and C-N bonds
- H2CO + NH3 --> amine (when NH3:H2CO > .2)
- H2CO + H2O --> diols (always dominate as H2O > H2CO)
- H2CO + H2CO --> -CH2-O-n (catalyzed by NH3 when NH3:H2CO > .005)
There is no kinetic data available for these reactions as the entire reaction is not verified nor well understood. These reactions are believed to take place during warm-up of the ice on grains which releases the molecules to react. These reactions begin at temperatures as low as 40K - 80K but may take place at even lower temperatures.
Note that many other reactions are listed on the UMIST RATE06 database.
Importance of observation
Formaldehyde appears to be a useful probe for astrochemists due to its low reactivity in the gas phase and to the fact that the 110 - 111 and 211 - 212 K-doublet transitions are rather clear. Formaldehyde has been used in many capacities and to investigate many systems including,
- * Determination of the 12C/13C ratio to be less than 50% in the galactic disc
- * Mapping of the kinematic features of dark clouds located near Gould's Belt of local bright stars
- * Determination of the temperature of molecular formation from the ratio of ortho-/para- H2CO. H2CO is a good candidate for this process because of the near zero probability of nuclear spin conversion in gas phase protostar environments[M. Tudorie ''et al''. 2006, ''Astronomy and Astrophysics'', 453, 755.].
- * Determination of the spatial density of H2 and dense gas mass in several galaxies with varying luminosity (see Subsequent Discoveries for list of galaxies)Rotational spectrum
Above is the rotational spectrum at the ground state vibrational level of H2CO at 30 K. This spectrum was simulated using Pgopher and S-Reduction Rotational constants from Muller ''et al.''[H. S. P. Muller ''et al''. 2000, ''Journal of Molecular Spectroscopy'', 200, 143.]. The observed transitions are the 6.2 cm 111 - 110 and 2.1 cm 212 - 211 K-doublet transitions. At right is the rotational energy level diagram. The ortho/para splitting is determined by the parity of Ka, ortho if Ka is odd and para if Ka is evenSynthesis and industrial production
Formaldehyde was first Chemical synthesis|reported by the Russian chemist Aleksandr Butlerov (1828-1886), but was conclusively identified by August Wilhelm von Hofmann.[J Read, Text-Book of Organic Chemistry, G Bell & Sons, London, 1935]
Formaldehyde is produced industrially by the catalytic oxidation of methanol. The most common catalysts are silver metal or a mixture of an iron oxide|iron and molybdenum trioxide|molybdenum or vanadium pentoxide|vanadium oxides. In the more commonly used FORMOX process methanol and oxygen react at ca 250-400 °C in presence of iron oxide in combination with molybdenum and/or vanadium to produce formaldehyde according to the chemical equation:[G. Reuss, W. Disteldorf, A. O. Gamer, A. Hilt, “Formaldehyde” in Ullmann’s Encyclopedia of Industrial Chemistry Wiley-VCH, 2005, Weinheim.]
- 2 methanol|CH3OH + oxygen|O2 → 2 H2CO + 2 water (molecule)|H2O
The silver-based catalyst is usually operated at a higher temperature, about 650 °C. Two chemical reactions on it simultaneously produce formaldehyde: that shown above and the dehydrogenation reaction:
- CH3OH → H2CO + hydrogen|H2
Formalin can be produced on a smaller scale using a whole range of other methods including conversion from ethanol instead of the normally-fed methanol feedstock. Such methods are of less commercial importance.
In principle formaldehyde could be generated by oxidation of methane, but this route is not industrially viable because the formaldehyde is more easily oxidized than methane.[
] Organic chemistry
Formaldehyde is a building block in the synthesis of many other compounds of specialized and industrial significance. It exhibits most of the chemical properties of other aldehydes but is more reactive. For example it is more readily oxidation|oxidized by atmospheric oxygen to formic acid (formic acid is found in ppm levels in commercial formaldehyde). Formaldehyde is a good electrophile, participating in electrophilic aromatic substitution reactions with aromatic compounds, and can undergo electrophilic addition reactions with alkenes and aromatics. Formaldehyde undergoes a Cannizzaro reaction in the presence of base (chemistry)|basic catalysts to produce formic acid and methanol.
Examples of organic synthetic applications
Condensation with acetaldehyde affords pentaerythritol, a chemical necessary in synthesizing PETN, a high explosive.
- 3 CH2O + 3 H2S → (CH2S)3 + 3 H2O
Industrial applications
Formaldehyde is a common building block for the synthesis of more complex compounds and materials. In approximate order of decreasing consumption, products generated from formaldehyde include urea formaldehyde resin, melamine resin, phenol formaldehyde resin, polyoxymethylene plastics, 1,4-butanediol, and methylene diphenyl diisocyanate.[
When reacted with phenol, urea, or melamine formaldehyde produces, respectively, hard thermoset phenol formaldehyde resin, urea formaldehyde resin, and melamine resin, which are commonly used in permanent adhesives such as those used in plywood or carpeting. It is used as the wet-strength resin added to sanitary paper products such as (listed in increasing concentrations injected into the paper machine headstock chest) facial tissue, table napkins, and roll towels. They are also foamed to make Thermal insulation|insulation, or casting|cast into moulded products. Production of formaldehyde resins accounts for more than half of formaldehyde consumption.
Formaldehyde is also a precursor to polyfunctional alcohols such as pentaerythritol, which is used to make paints and explosives. Other formaldehyde derivatives include methylene diphenyl diisocyanate, an important component in polyurethane paints and foams, and hexamine, which is used in phenol-formaldehyde resins as well as the explosive RDX.
The textile industry uses formaldehyde-based resins as finishers to make fabrics crease-resistant.][FORMALDEHYDE IN CLOTHING AND OTHER TEXTILES]
It is also used as an ingredient by some shampoo manufacturers.
Miscellaneous applications
Formaldehyde is a common component of many niche uses. Formaldehyde, along with 18 Concentration#molarity|M (concentrated) sulfuric acid (the entire solution often called the Marquis reagent)[DanceSafe: testing kit info], is used as an MDMA "testing kit" by such groups as Dancesafe as well as MDMA consumers. The solution alone cannot verify the presence of MDMA but reacts with many other chemicals that the MDMA tablet itself may be adulterated with. The reaction itself produces colors that correlate with these components.
As a disinfectant and biocide
An aqueous solution of formaldehyde can be useful as a disinfectant as it kills most bacterium|bacteria and fungi (including their spores). It is also used as a preservative in vaccines. Formaldehyde solutions are applied topically in medicine to dry the skin, such as in the treatment of warts. Many aquarists use formaldehyde as a treatment for the parasites ichthyophthirius and Cryptocaryon irritans.[University of Florida - Use of Formalin to Control Fish Parasites http://edis.ifas.ufl.edu/VM061]
Formaldehyde preserves or Fixation (histology)|fixes tissue or cells by irreversibly cross-linking primary amino groups in proteins with other nearby nitrogen atoms in protein or DNA through a -CH2- linkage. This is exploited in ChIP-on-chip transcriptomics experiments. Formaldehyde is also used as a denaturing agent in RNA gel electrophoresis, preventing RNA from forming secondary structures.
In photography
Formaldehyde is still used in low concentrations for process C-41 (color negative film) stabilizer in the final wash step, as well as in the E-6 process|process E-6 pre-bleach step, to obviate the need for it in the final wash.
Tissue fixative and embalming agent
Formaldehyde solutions are used as a Fixation (histology)|fixative for microscopy and histology. Formaldehyde-based solutions are also used in embalming to disinfect and temporarily preserve human and animal remains. It is the ability of formaldehyde to fix the tissue that produces the tell-tale firmness of flesh in an embalmed body. Several European countries restrict the use of formaldehyde, including the import of formaldehyde-treated products and embalming, and the European Union is considering a complete ban on formaldehyde usage (including embalming), subject to a review of List 4B of the Technical Annex to the Report from the Commission to the European Parliament and the Council on the Evaluation of the Active Substances of Plant Protection Products by the European Commission Services. Countries with a strong tradition of embalming corpses, such as Ireland and other colder-weather countries, have raised concerns. The European Union decided on September 22, 2007 to ban Formaldehyde use throughout Europe due to its carcinogenic properties.[Formaldehyde Ban set for 22 Sept 2007]
Safety
Occupational exposure to formaldehyde by inhalation is mainly from three types of sources: Thermal decomposition|thermal or chemical decomposition of formaldehyde-based resins, formaldehyde emission from aqueous solutions (for example, embalming fluids), and the production of formaldehyde resulting from the combustion of a variety of organic compounds (for example, exhaust gases). Formaldehyde can be toxic, allergenic, and carcinogenic.[IARC Press Release June 2004, http://www.iarc.fr/ENG/Press_Releases/archives/pr153a.html] Because formaldehyde resins are used in many construction materials it is one of the more common indoor air pollutants.[Indoor Air Pollution in California, Final Report, California Air Resources Board (2005) http://www.arb.ca.gov/research/indoor/ab1173/finalreport.htm, at pages 65 – 70.] At concentrations above 3 ppb in air formaldehyde can irritate the eyes and mucous membranes, resulting in watery eyes. Formaldehyde inhaled at this concentration may cause headaches, a burning sensation in the throat, and difficulty breathing, as well as triggering or aggravating asthma symptoms.[ http://www.oehha.ca.gov/air/chronic_rels/AllChrels.html California Office Of Health Hazard Assessment ][Symptoms of Low-Level Formaldehyde Exposures, Health Canada, http://www.hc-sc.gc.ca/iyh-vsv/environ/formaldehyde_e.html]
Formaldehyde is classified as a probable human carcinogen by the U.S. Environmental Protection Agency. The International Agency for Research on Cancer (IARC) has determined that there is "sufficient evidence" that occupational exposure to formaldehyde causes nasopharyngeal cancer in humans. [http://monographs.iarc.fr/ENG/Monographs/vol88/volume88.pdf "Formaldehyde".]
The United States Environmental Protection Agency (USEPA) allows no more than 0.016 ppm formaldehyde in the air in new buildings constructed for that agency.[ Testing for Indoor Air Quality, Baseline IAQ, and Materials, http://www.epa.gov/rtp/new-bldg/environmental/s_01445.htm] On April 11th, 2008, FEMA announced that all trailers purchased by that agency in the future must meet the same standard.[ In the US, FEMA limits formaldehyde in trailers, Boston.com, referenced 9/4/2008http://www.boston.com/news/nation/washington/articles/2008/04/11/fema_limits_formaldehyde_in_trailers/]
Formaldehyde can cause allergies and is part of the standard patch test series. People with formaldehyde allergy are advised to avoid formaldehyde releasers as well (''e.g.'', Quaternium-15, imidazolidinyl urea, and diazolidinyl urea).FEMA trailer incidents
Hurricane Katrina & Rita
In the U.S. the Federal Emergency Management Agency (FEMA) provided travel trailers and mobile homes starting in 2006 for habitation by residents of the U.S. gulf coast displaced by Hurricane Katrina and Hurricane Rita. Some of the people who moved into the trailers complained of breathing difficulties, nosebleeds, and persistent headaches. Formaldehyde-catalyzed resins were used in the production of these homes.
The United States Centers For Disease Control and Prevention (CDC) performed indoor air quality testing for formaldehyde [http://www.cdc.gov/niosh/nmam/pdfs/2016.pdf] in some of the units. On Thursday, February 14, 2008 the CDC announced that potentially hazardous levels of formaldehyde were found in many of the travel trailers and mobile homes provided by the agency.[Formaldehyde Levels in FEMA-Supplied Trailers][ATSDR - Minimal Risk Levels for Hazardous Substances (MRLs)]. Levels measured ranged from 3 ppb to 590 ppb.[FEMA: CDC Releases Results Of Formaldehyde Level Tests]
The Federal Emergency Management Agency, which requested the testing by the CDC, said it would work aggressively to relocate all residents of the temporary housing as soon as possible. Lawsuits are being filed against FEMA as a result of the exposures.[Suit Filed Over FEMA Trailer Toxins - washingtonpost.com]
Iowa Floods of 2008
Also in the U.S., problems arose in trailers again provided by FEMA to residents displaced by the Iowa Flood of 2008|Iowa floods of 2008. A couple months after moving to the trailers, occupants reported violent coughing, headaches, as well as Asthma, Bronchitis, and other problems. Tests showed that in some trailers, levels of formaldehyde exceeded the limits recommended by the U.S. Environmental Protection Agency and American Lung Association.Contaminant in Food
Scandals have broken in both 2005 Indonesia food scare and 2007 Vietnam food scare regarding the addition of formaldehyde to foods to extend shelf life. Foods known to be contaminated include noodles, salted fish, tofu, and rumors of chicken and beer. In humans, it is known to cause a number of detrimental effects including cancer.
References
External links
- International Chemical Safety Card 0275 (''gas'')
- International Chemical Safety Card 0695 (''solution'')
- "Formaldehyde", IARC Monograph
- Formaldehyde (gas) from the 11th Report on Carcinogens of the U.S. National Toxicology Program (.pdf file)
- Formaldehyde fact sheet from the Australian National Pollutant Inventory
- NIOSH Pocket Guide to Chemical Hazards
- Process C-41 Using KODAK FLEXICOLOR Chemicals Publication Z-131
- Formaldehyde Council
- Formaldehyde Data Sheet, ChemSub Online
- Prevention guide – Formaldehyde in the work place
- National Institute for Occupational Safety and Health - Formaldehyde Page
Category:Aldehydes
Category:Carcinogens
Category:IARC Group 1 carcinogens
Category:Hazardous air pollutants
Category:Anatomical preservation
Category:Occupational safety and health
simple:Formaldehyde
Related Images- A rotational spectrum of H2CO at the ground state vibrational level at 30 K.
- The rotational energy level diagram of H2CO at 30 K shown with ortho/para splitting.
Sources: StartLearningNow, Wikipedia | Usage license: GNU FDL
 |
Welcome to Start Learning Now.
Explore to your heart's content, and we hope you enjoy reading the material we
have assembled for you here! |
 |
| | | | |
Related News
|
|
Further Resources
|
|
Related Resources
search
|
|
