Formaldehyde
Formaldehyde, CH2O, is the first of the series of aliphatic aldehydes. Russian chemist Aleksandr Butlerov is credited with the history of formaldehyde in 1859 and August Wilhelm von Hofmann synthesized it in 1868 and identified it as the first member of the aldehyde. It is prepared commercially by catalytic vapor phase oxidation of methanol using air as the oxidizing agent and heated silver, copper, alumina or coke as catalysts. There has been significant research activity to develop new processes for producing formaldehyde through three ways; either directly from methane by partial oxidation, from dehydrogenation of methanol (which would produce anhydrous and or highly concentrated formaldehyde solutions) or from methylal produced from methanol and formaldehyde but no commercial units are known to exist [1]. Formaldehyde is a basic chemical building block for the production of a wide range of chemicals finding a wide variety of end uses such as wood products, plastics, and coatings, e.g. amino and phenolic resins 1, 4-butanediol, polyols. It is also a by-product of combustion and certain other natural processes. Thus, it may be present in substantial concentrations both indoors and outdoors [2].
Formaldehyde is a flammable colorless gas and has a pungent suffocating odor. It can cause watery eyes, burning sensations in the eyes and throat and may trigger attacks in people. It has also been shown to cause cancer in animals and humans. It has a density of 1.067, a melting point of -92◦C, a boiling point of -19.5◦C. Ignition temperature is about 300◦C(572◦F). It is very soluble in water, up to 55%; soluble in alcohol, ether [3]. Its structure is trigonal planar and its polarity is molecular (the partial specific negative charge is on the oxygen atom and the partial specific positive charge is on the carbon atom). It is very reactive and combines readily with many substances. Formaldehyde is used in the form of anhydrous monomer solutions, polymers, and derivatives. For example, it exist as a mixture of oligomers, HO (CH2O)nH. Their distribution has been determined for 6-50wt% HCHO solutions with low methanol using nmr and gas chromatography techniques. Chemically, formaldehyde condenses with itself in an aldol
type reaction.

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The reaction is catalyzed by a base and a divalent metal such as calcium. The intermediary steps taking place are aldol reactions, reverse Aldol reactions, and aldose-ketose isomerizations. The reaction begins with two formaldehyde molecules condensing to make glycolaldehyde 1 which further reacts in an aldol reaction with another equivalent of formaldehyde to make glyceraldehyde 2. An aldose-ketose isomerization of 2 forms dihydroxyketone 3 which can react with 2 to form ribulose 4, and through another isomerization ribose 5. Molecule 3 also can react with formaldehyde to produce tetrulose 6 and then aldoltetrose 7. Molecule 7 can split into 2 in a retro-aldol reaction. Also,with acid catalysts in the liquid phase, formaldehyde and alcohols give formals, e.g. dimethoxymethane from methanol. Also, formaldehyde reacts with syn gas (CO, H2) to produce added value products like glycolaldehyde and glycolic [1].
Formaldehyde could induce genetic alterations which first appeared in the 1940's with the publication of studies describing it as a weak mutagen in Drosophila larvae, fungi and bacteria. More recent studies have demonstrated that formaldehyde can induce single-stranded DNA breaks, DNA-protein crosslinks, sister chromatid exchanges, chromosome aberrations and mutations in a variety of cultured mammalian cell types (including human). Genotoxic effects have also been recently observed in yeast, bacteria and Drosophila. Formaldehyde is a normal biological intermediate that appears to be present in all biological tissues. In the form of'active formaldehyde' (N5, N10-methylene tetrahydrofolate) it is used in mammals for the biosynthesis of purines, thymine, methionine and serine. Active formaldehyde is produced from serine (via the enzyme L-serine: tetrahydrofolate-5, 10-methylene transferase) and glycine (via the glycine cleavage reaction). A variety of other compounds containing N-, O-, and S-methyl groups also yield formaldehyde as a primary metabolic product.The reactivity of formaldehyde toward biological macromolecules has been well documented. Extensive crosslinking of DNA and protein has been observed in a variety of mammalian cells in culture following treatment with formaldehyde. These cross-links are rapidly repaired (repair half-time <4 h) in mouse LI210 and human bronchial cells. Repair probably proceeds via an excision repair process, which may account for the small numbers of single-strand DNA breaks observed in formaldehydetreated cells. Methods are not yet available to quantitate the molecular dosimetry of formaldehyde-induced DNA adducts. Since formaldehyde is rapidly metabolized and incorporated into normal macromolecules, the actual isolation and quantitation of DNA adducts is crucial. Furthermore, it is essential that these measurements be made following inhalation exposure of animals, wherein all defense mechanisms can function. This will permit risk estimation in laboratory animals, based on molecular dosimetry and the observed tumor response. If such data are proportional, the observed response could be extended to exposure levels of environmental concern. Providing ultrasensitive techniques can be developed, they could also be applied to cases of known human exposure. Confounding factors such as life-style, smoking habits or health status may affect human dosimetry and response to formaldehyde exposure [4].
The recent news on Formaldehyde is that EPA (Environmental Protection Agency) who is in charge of cases on formaldehyde failed to support the chemical’s link to leukemia and other health problems but concluded that it causes cancer in the nose, nasal cavity, and upper throat. The NCR (National Academies’ National Research Council) said "EPA should revisit its arguments and include detailed descriptions of the criteria that were used to weigh evidence and assess causality. The report also notes that EPA's draft assessment provides "little discussion about how asthma could be caused or exacerbated by formaldehyde exposure” [5].
Formaldehyde is causing more damage than ever. Because of its relatively low cost, high purity, and variety of chemical reactions, formaldehyde has become one of the world’s most important industrial and research chemicals. With the recent news, as consumers we should know about the effects of formaldehyde from two or more sources. Also ask about the formaldehyde content of pressed wood products, including materials, cabinetry and furniture, before you purchase them. You may wish to reduce your exposure as much as possible by purchasing exterior-grade products which emit less formaldehyde.


Bibliography

  1. Hoboken, N.J. (2007). Kirk-Othmer Concise Encyclopedia of Chemical Technology.
Chemistry Technical-Encyclopedias.Vol 5. Hoboken, N.J. Wiley-Interscience.
2. Laura, L. (2010). Environmental health sourcebook: Basic Consumer Health Information
the Environment and its Effects on Human Health. 3rd ed. Detroit, MI.
Omnigraphics.
3. O'Neil, Maryadele. (2006).The Merck index : an encyclopedia of chemicals, drugs, an
biological/.The Merck index: an encyclopedia of chemicals, drugs, and
biologicals / Maryadele J. O'Neil, editor ... [et al.].14ed. WhiteHouse station, N.J.
4. Swenberg, J.A et al. (1983). Non-linear biological responses to formaldehyde and their
implications for carcinogenic risk assessment. Chemical Industry Institute of
Toxicology.http://toxicology.usu.edu/endnote/Non-linear-biological-responses.pdf.
5.Hess, G. (2011, April 12). Doubting EPA on Formaldehyde. Chemical and Engineering
News. http://pubs.acs.org/cen/news/89/i16/8916news.html.