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Halocarbon

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Halocarbon

Halocarbon compounds are

Chemical bonds to carbon
Core organic chemistry Many uses in chemistry
Academic research, but no widespread use Bond unknown
CH He
CLi CBe CB CC CN CO CF Ne
CNa CMg CAl CSi CP CS CCl CAr
CK CCa CSc CTi CV CCr CMn CFe CCo CNi CCu CZn CGa CGe CAs CSe CBr CKr
CRb CSr CY CZr CNb CMo CTc CRu CRh CPd CAg CCd CIn CSn CSb CTe CI CXe
CCs CBa CHf CTa CW CRe COs CIr CPt CAu CHg CTl CPb CBi CPo CAt Rn
Fr CRa Rf Db CSg Bh Hs Mt Ds Rg Cn Uut Fl Uup Lv Uus Uuo
CLa CCe CPr CNd CPm CSm CEu CGd CTb CDy CHo CEr CTm CYb CLu
Ac CTh CPa CU CNp CPu CAm CCm CBk CCf CEs Fm Md No Lr
  • Anderson v. Grace (1986), 628 F. Supp. 1219, Massachusetts, USA , settled between the parties, reviewed in Harr, J., Ed.; Asher, M., Ed. (1996), A Civil Action, Minneapolis, MN, USA: Sagebrush Education Resources 
  • Carson, R. (1962), Silent Spring, Boston, MA, USA: Houghton Mifflin 
  • Flinn, F.B.; Jarvik, N.E. (1936), "Action of certain chlorinated naphthalenes on the liver", Proceedings of the Society for Experimental Biology and Medicine 35: 118,  
  • Jensen, S. (1966), "Report of a new chemical hazard", New Scientist 32: 612 
  • Molina, M.J.; Rowland, F.S. (1974), "Stratospheric sink for chlorofluoromethanes: chlorine atom-catalysed destruction of ozone", Nature 249: 810,  
  • Müller, P.H. (1948), "Dichloro-diphenyl-trichloroethane and newer insecticides" (PDF), Nobel Lecture 
  • Owens v. Monsanto (2001), 96-CV-440, Exhibit 3A03F (PDF), Alabama, USA , cited in Chemical Industry Archives, Anniston Case, by Environmental Working Group, Washington, DC, 2002
  • Scott, C.S., Ed.; Cogliano, V.J., Ed. (2000), "Trichloroethylene Health Risks--State of the Science", Environmental Health Perspectives 108 (S2),  
  • Teleky, L. (1927), "Die pernakrankheit", Klinische Wochenschrift (Berlin: Springer), Jahrgänge 6: 845 
  • U.S. National Academies of Science, Current Projects System (2004), Assessing the Human Health Risks of Trichloroethylene 
  • United States, Environmental Protection Agency (2004), Integrated Risk Information System, Trichloroethylene (CASRN 79-01-6) 
  • United States, Environmental Protection Agency (2010), PFOA Stewardship Program (begun in 2006) 

References

  1. ^ Yoel Sasson. "Formation of Carbon–Halogen Bonds (Cl, Br, I)" in Patai's Chemistry of Functional Groups (2009). Wiley-VCH, Weinheim. doi:10.1002/9780470682531.pat0011
  2. ^ M. Rossberg et al. “Chlorinated Hydrocarbons” in Ullmann’s Encyclopedia of Industrial Chemistry 2006, Wiley-VCH, Weinheim. doi:10.1002/14356007.a06_233.pub2
  3. ^ Gordon W. Gribble (1998), "Naturally Occurring Organohalogen Compounds",  .
  4. ^ Gordon W. Gribble (1999), "The diversity of naturally occurring organobromine compounds",  .
  5. ^ Gordon W. Gribble (2002), Neilson, A. H., ed., "Naturally Occurring Organofluorines", Organofluorines 3n: 121–136,  .
  6. ^ Phyllis A. Lyday "Iodine and Iodine Compounds" in Ullmann's Encyclopedia of Industrial Chemistry, Wiley-VCH, Weinheim, 2005.doi:10.1002/14356007.a14_381
  7. ^ Climate Change 2007: The Physical Science Basis. Summary for Policymakers, page 3
  8. ^ Villemur, R.; Lanthier, M.; Beaudet, R. ©J.; Lépine, F. §O. (2006). "TheDesulfitobacteriumgenus". FEMS Microbiology Reviews 30 (5): 706–733.  

Notes

See also

[8] Halocarbons, including those that might not be hazards in themselves, can present

Since the 1970s there have been longstanding, unresolved controversies over potential health hazards of trichloroethylene (TCE) and other halocarbon solvents that had been widely used for industrial cleaning (Anderson v. Grace 1986) (Scott & Cogliano 2000) (U.S. National Academies of Science 2004) (United States 2004). More recently perfluorooctanoic acid (PFOA), a precursor in the most common manufacturing process for Teflon and also used to make coatings for fabrics and food packaging, became a health and environmental concern starting in 2006 (United States 2010 (begun in 2006)), suggesting that halocarbons, though thought to be among the most inert, may also present hazards.

In 1962 a book by U.S. biologist Rachel Carson (Carson 1962) started a storm of concerns about environmental pollution, first focused on DDT and other pesticides, some of them also halocarbons. These concerns were amplified when in 1966 Swedish chemist Soren Jensen reported widespread residues of PCBs among Arctic and sub-Arctic fish and birds (Jensen 1966). In 1974, mexican chemist Mario Molina and U.S. chemist Sherwood Rowland predicted that common halocarbon refrigerants, the chlorofluorocarbons (CFCs), would accumulate in the upper atmosphere and destroy protective ozone (Molina & Rowland 1974). Within a few years, ozone depletion was being observed above Antarctica, leading to bans on production and use of chlorofluorocarbons in many countries. In 2007, the Intergovernmental Panel on Climate Change (IPCC) said halocarbons were a direct cause of global warming.[7]

The stability of halocarbons tended to encourage beliefs that they were mostly harmless, although in the mid-1920s physicians reported workers in polychlorinated naphthalene manufacturing suffering from chloracne (Teleky 1927), and by the late 1930s it was known that workers exposed to PCNs could die from liver disease (Flinn & Jarvik 1936) and that DDT would kill mosquitos and other insects (Müller 1948). By the 1950s, there had been several reports and investigations of workplace hazards. In 1956, for example, after testing hydraulic oils containing PCBs, the U.S. Navy found that skin contact caused fatal liver disease in animals and rejected them as "too toxic for use in a submarine" (Owens v. Monsanto 2001).

Hazards

A few halocarbons, including acid halides like acetyl chloride, are highly reactive; these are rarely found outside chemical processing. The widespread uses of halocarbons were often driven by observations that most of them were more stable than other substances. They may be less affected by acids or alkalis; they may not burn as readily; they may not be attacked by bacteria or molds; or they may not be affected as much by sun exposure.

Haloaromatics include the former Aroclors (Monsanto Company trademark for polychlorinated biphenyls, PCBs), once widely used in power transformers and capacitors and in building caulk, the former Halowaxes (Union Carbide trademark for polychlorinated naphthalenes, PCNs), once used for electrical insulation, and the chlorobenzenes and their derivatives, used for disinfectants, pesticides such as dichloro-diphenyl-trichloroethane (DDT, 1,1,1-trichloro-2,2-bis(p-chlorophenyl)ethane), herbicides such as 2,4-D (2,4-dichlorophenoxyacetic acid), askarel dielectrics (mixed with PCBs, no longer used in most countries), and chemical feedstocks.

Haloalkenes have also been used as solvents, including perchloroethylene (Perc, tetrachloroethene), widespread in dry cleaning, and trichloroethylene (TCE, 1,1,2-trichloroethene). Other haloalkenes have been chemical building blocks of plastics such as polyvinyl chloride ("vinyl" or PVC, polymerized chloroethene) and Teflon (duPont trademark for polymerized tetrafluoroethene, PTFE).

Before they became strictly regulated, the general public often encountered haloalkanes as paint and cleaning solvents such as trichloroethane (1,1,1-trichloroethane) and carbon tetrachloride (tetrachloromethane), pesticides like 1,2-dibromoethane (EDB, ethylene dibromide), and refrigerants like Freon-22 (duPont trademark for chlorodifluoromethane). Some haloalkanes are still widely used for industrial cleaning, such as methylene chloride (dichloromethane), and as refrigerants, such as R-134a (1,1,1,2-tetrafluoroethane).

Common uses for halocarbons have been as solvents, pesticides, refrigerants, fire-resistant oils, ingredients of elastomers, adhesives and sealants, electrically insulating coatings, plasticizers, and plastics. Many halocarbons have specialized uses in industry. One halocarbon, sucralose, is a sweetener.

The first halocarbon commercially used was Murex brandaris marine snail.

Uses

This treatment is seldom used today as a stand-alone therapy despite the rapid improvement of patients immediately following administration. The major disadvantage of iodide treatment lies in the fact that excessive stores of TH accumulate, slowing the onset of action of thioamides (TH synthesis blockers). In addition, the functionality of iodides fades after the initial treatment period. An "escape from block" is also a concern, as extra stored TH may spike following discontinuation of treatment.

Six mg of iodide a day can be used to treat patients with proteolysis of thyroglobulin, which permits TH to be synthesized and stored in colloid, but not released into the bloodstream.

The thyroxin hormones are essential for human health, hence the usefulness of iodized salt.

Organoiodine compounds, called organic iodides, are similar in structure to organochlorine and organobromine compounds, but the C-I bond is weaker. Many organic iodides are known, but few are of major industrial importance. Iodide compounds are mainly produced as nutritional supplements.[6]

Organoiodine compounds, including biological derivatives

[5][4][3] A large amount of the naturally occurring halocarbons are created by wood fire,

Natural halocarbons

A few halocarbons are produced in massive amounts by microorganisms. For example, several million tons of methyl bromide are estimated to be produced by marine organisms annually. Most of the halocarbons encountered in everyday life – solvents, medicines, plastics – are man-made. The first synthesis of halocarbons was achieved in the early 1800s. Production began accelerating when their useful properties as solvents and anesthetics were discovered. Development of plastics and synthetic elastomers has led to greatly expanded scale of production. A substantial percentage of drugs are halocarbons.

History and context

The halogen atoms in halocarbon molecules are often called "substituents," as though those atoms had been substituted for hydrogen atoms. However halocarbons are prepared in many ways that do not involve direct substitution of halogens for hydrogens.

Halocarbons are typically classified in the same ways as the similarly hydrogen atoms occupying the molecular sites of the halogen atoms in halocarbons. Among the chemical families are:[2]

Examples of organohalogens-chlorides

Chemical families

Contents

  • Chemical families 1
  • History and context 2
    • Natural halocarbons 2.1
  • Organoiodine compounds, including biological derivatives 3
  • Uses 4
  • Hazards 5
  • See also 6
  • Notes 7
  • References 8

For information on inorganic halide chemistry, see halide.

Many synthetic organic compounds such as Prozac have trifluoromethyl groups.

[1]

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