Heptachlor

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Heptachlor
(+)-Heptachlor.svg
Heptachlor-3D-balls.png
Names
Preferred IUPAC name
1,4,5,6,7,8,8-Heptachloro-3a,4,7,7a-tetrahydro-1H-4,7-methanoindene
Identifiers
3D model (JSmol)
ChEBI
ChEMBL
ChemSpider
ECHA InfoCard 100.000.876 OOjs UI icon edit-ltr-progressive.svg
KEGG
PubChem CID
UNII
  • InChI=1S/C10H5Cl7/c11-4-2-1-3-5(4)9(15)7(13)6(12)8(3,14)10(9,16)17/h1-5H Yes check.svgY
    Key: FRCCEHPWNOQAEU-UHFFFAOYSA-N Yes check.svgY
  • InChI=1/C10H5Cl7/c11-4-2-1-3-5(4)9(15)7(13)6(12)8(3,14)10(9,16)17/h1-5H
    Key: FRCCEHPWNOQAEU-UHFFFAOYAM
  • ClC1/C=C\C2C3(Cl)C(\Cl)=C(\Cl)C(Cl)(C12)C3(Cl)Cl
Properties
C10H5Cl7
Molar mass 373.32 g/mol
AppearanceWhite to tan solid
Odor Camphorous
Density 1.58 g/cm3
Melting point 95 to 96 °C (203 to 205 °F; 368 to 369 K)
Boiling point 135 to 145 °C (275 to 293 °F; 408 to 418 K) at 1-1.5 mmHg
0.0006% (20°C) [1]
Vapor pressure 0.0003 mmHg (25°C) [1]
Hazards
Flash point noncombustible [1]
Lethal dose or concentration (LD, LC):
116 mg/kg (oral, guinea pig)
40 mg/kg (oral, rat)
100 mg/kg (oral, rat)
68 mg/kg (oral, mouse)
100 mg/kg (oral, hamster) [2]
50 mg/kg (cat, oral) [2]
150 mg/m3 (cat, 4 hr)
200 mg/m3 (mammal, 4 hr) [2]
NIOSH (US health exposure limits):
PEL (Permissible)
TWA 0.5 mg/m3 [skin] [1]
REL (Recommended)
Ca TWA 0.5 mg/m3 [skin] [1]
IDLH (Immediate danger)
Ca [35 mg/m3] [1]
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
X mark.svgN  verify  (what is  Yes check.svgYX mark.svgN ?)

Heptachlor is an organochlorine compound that was used as an insecticide. Usually sold as a white or tan powder, heptachlor is one of the cyclodiene insecticides. In 1962, Rachel Carson's Silent Spring questioned the safety of heptachlor and other chlorinated insecticides. Due to its highly stable structure, heptachlor can persist in the environment for decades. In the United States, the Environmental Protection Agency has limited the sale of heptachlor products to the specific application of fire ant control in underground transformers. The amount that can be present in different foods is regulated. [3]

Contents

Synthesis

Analogous to the synthesis of other cyclodienes, heptachlor is produced via the Diels-Alder reaction of hexachlorocyclopentadiene and cyclopentadiene. The resulting adduct is chlorinated followed by treatment with hydrogen chloride in nitromethane in the presence of aluminum trichloride or with iodine monochloride. [4]

Compared to chlordane, it is about 3–5 times more active as an insecticide, but more inert chemically, being resistant to water and caustic alkalies. [4]

Metabolism

Soil microorganisms transform heptachlor by epoxidation, hydrolysis, and reduction. When the compound was incubated with a mixed culture of organisms, chlordene (hexachlorocyclopentadine, its precursor) formed, which was further metabolized to chlordene epoxide. Other metabolites include 1-hydroxychlordene, 1-hydroxy-2,3-epoxychlordene, and heptachlor epoxide. Soil microorganisms hydrolyze heptachlor to give ketochlordene. Rats metabolize heptachlor to the epoxide 1-exo-1-hydroxyheptachlor epoxide and 1,2-dihydrooxydihydrochlordene. When heptachlor epoxide was incubated with microsomal preparations form liver of pigs and from houseflies, the products found were diol and 1-hydroxy-2,3-epoxychlordene. [4] The metabolic scheme in rats shows two pathways with the same metabolite. The first involves following scheme: heptachlor → heptachlor epoxide → dehydrogenated derivative of 1-exo-hydroxy-2,3-exo-epoxychlordene → 1,2-dihydrooxydihydrochlordene. The second involves: heptachlor → 1-exo-hydroxychlordene → 1-exo-hydroxy, 2,3-exo-epoxychlordene → 1,2-dihydrooxydihydrochlordene. [5]

Environmental impact

Heptachlor is a persistent organic pollutant (POP). It has a half life of ~1.3-4.2 days (air), ~0.03-0.11 years (water), and ~0.11-0.34 years (soil). One study described its half life to be 2 years and claimed that its residues could be found in soil 14 years after its initial application. Like other POPs, heptachlor is lipophilic and poorly soluble in water (0.056 mg/L at 25 °C), thus it tends to accumulate in the body fat of humans and animals.

Heptachlor epoxide is more likely to be found in the environment than its parent compound. The epoxide also dissolves more easily in water than its parent compound and is more persistent. Heptachlor and its epoxide absorb to soil particles and evaporate. [6]

The range of oral rat LD50 values are 40 mg/kg to 162 mg/kg. Daily oral doses of heptachlor at 50 and 100 mg/kg were found to be lethal to rats after 10 days. For heptachlor epoxide, the oral LD50 values ranging from 46.5 to 60 mg/kg. With rat oral of LD5047mg/kg, heptachlor epoxide is more toxic. A product of hydrogenation of heptachlor, β-dihydroheptachlor, has high insecticidal activity and low mammalian toxicity, rat oral LD50>5,000mg/kg. [4]

Human impact

Humans may be exposed to heptachlor through drinking water and foods, including breast milk. [6] Heptachlor epoxide is derived from a pesticide that was banned in the U.S. in the 1980s. It is still found in soil and water supplies and can turn up in food.[ citation needed ] It can be passed along in breast milk.[ citation needed ]

The International Agency for Research on Cancer and the EPA have classified the compound as a possible human carcinogen. Animals exposed to heptachlor epoxide during gestation and infancy are found to have changes in nervous system and immune function. Exposure to higher doses of heptachlor in newborn animals leads to decreased body weight and death. [5]

The U.S. EPA MCL for drinking water is 0.0004 mg/L for heptachlor and 0.0002 mg/L for heptachlor epoxide. The U.S. FDA limit on food crops is 0.01 ppm, in milk 0.1 ppm, and on edible seafoods 0.3 ppm. The Occupational Safety and Health Administration has limit of 0.5 mg/m3 (cubic meter of workplace air) for 8-hour shifts and 40-hour work weeks. [6]

An ATSDR report in 1993 found no studies with respect to death in humans after oral exposure to heptachlor or heptachlor epoxide.

Chemical properties

The octanol-water partition coefficient (Kow) of heptachlor is ~105.27. Henry's Law constant is 2.3 · 10−3atm-m3/mol and the vapor pressure is 3 · 10−4mmHg at 20 °C. [7] [8]

Related Research Articles

Chlordane, or chlordan, is an organochlorine compound that was used as a pesticide. It is a white solid. In the United States, chlordane was used for termite-treatment of approximately 30 million homes until it was banned in 1988. Chlordane was banned 10 years earlier for food crops like corn and citrus, and on lawns and domestic gardens.

<span class="mw-page-title-main">1,2-Dibromoethane</span> Chemical compound

1,2-Dibromoethane, also known as ethylene dibromide (EDB), is an organobromine compound with the chemical formula C
2H
4Br
2. Although trace amounts occur naturally in the ocean, where it is probably formed by algae and kelp, it is mainly synthetic. It is a dense colorless liquid with a faint, sweet odor, detectable at 10 ppm, and is a widely used and sometimes-controversial fumigant. The combustion of 1,2-dibromoethane produces hydrogen bromide gas that is significantly corrosive.

<span class="mw-page-title-main">Chlorfenvinphos</span> Chemical compound

Chlorfenvinphos is an organophosphorus compound that was widely used as an insecticide and an acaricide. The molecule itself can be described as an enol ester derived from dichloroacetophenone and diethylphosphonic acid. Chlorfenvinphos has been included in many products since its first use in 1963. However, because of its toxic effect as a cholinesterase inhibitor it has been banned in several countries, including the United States and the European Union. Its use in the United States was cancelled in 1991.

<span class="mw-page-title-main">Ethion</span> Chemical compound

Ethion (C9H22O4P2S4) is an organophosphate insecticide. Ethion is known to affect a neural enzyme called acetylcholinesterase and prevent it from working.

Demeton-S-methyl is an organic compound with the molecular formula C6H15O3PS2. It was used as an organothiophosphate acaricide and organothiophosphate insecticide. It is flammable. With prolonged storage, Demeton-S-methyl becomes more toxic due to formation of a sulfonium derivative which has greater affinity to the human form of the acetylcholinesterase enzyme, and this may present a hazard in agricultural use.

<span class="mw-page-title-main">Dieldrin</span> Chemical compound

Dieldrin is an organochlorine compound originally produced in 1948 by J. Hyman & Co, Denver, as an insecticide. Dieldrin is closely related to aldrin, which reacts further to form dieldrin. Aldrin is not toxic to insects; it is oxidized in the insect to form dieldrin which is the active compound. Both dieldrin and aldrin are named after the Diels-Alder reaction which is used to form aldrin from a mixture of norbornadiene and hexachlorocyclopentadiene.

<span class="mw-page-title-main">2-Butoxyethanol</span> Chemical compound

2-Butoxyethanol is an organic compound with the chemical formula BuOC2H4OH (Bu = CH3CH2CH2CH2). This colorless liquid has a sweet, ether-like odor, as it derives from the family of glycol ethers, and is a butyl ether of ethylene glycol. As a relatively nonvolatile, inexpensive solvent, it is used in many domestic and industrial products because of its properties as a surfactant. It is a known respiratory irritant and can be acutely toxic, but animal studies did not find it to be mutagenic, and no studies suggest it is a human carcinogen. A study of 13 classroom air contaminants conducted in Portugal reported a statistically significant association with increased rates of nasal obstruction and a positive association below the level of statistical significance with a higher risk of obese asthma and increased child BMI.

<span class="mw-page-title-main">Aldrin</span> Chemical compound

Aldrin is an organochlorine insecticide that was widely used until the 1990s, when it was banned in most countries. Aldrin is a member of the so-called "classic organochlorines" (COC) group of pesticides. COCs enjoyed a very sharp rise in popularity during and after World War II. Other noteworthy examples of COCs include dieldrin and DDT. After research showed that organochlorines can be highly toxic to the ecosystem through bioaccumulation, most were banned from use. Before the ban, it was heavily used as a pesticide to treat seed and soil. Aldrin and related "cyclodiene" pesticides became notorious as persistent organic pollutants.

2-Chloroethanol (also called ethylene chlorohydrin or glycol chlorohydrin) is an organic chemical compound with the chemical formula HOCH2CH2Cl and the simplest beta-halohydrin (chlorohydrin). This colorless liquid has a pleasant ether-like odor. It is miscible with water. The molecule is bifunctional, consisting of both an alkyl chloride and an alcohol functional group.

<span class="mw-page-title-main">Mirex</span> Chemical compound

Mirex is an organochloride that was commercialized as an insecticide and later banned because of its impact on the environment. This white crystalline odorless solid is a derivative of cyclopentadiene. It was popularized to control fire ants but by virtue of its chemical robustness and lipophilicity it was recognized as a bioaccumulative pollutant. The spread of the red imported fire ant was encouraged by the use of mirex, which also kills native ants that are highly competitive with the fire ants. The United States Environmental Protection Agency prohibited its use in 1976. It is prohibited by the Stockholm Convention on Persistent Organic Pollutants.

<span class="mw-page-title-main">Methoxychlor</span> Synthetic organochloride insecticide, now obsolete.

Methoxychlor is a synthetic organochloride insecticide, now obsolete. Tradenames for methoxychlor include Chemform, Maralate, Methoxo, Methoxcide, Metox, and Moxie.

<span class="mw-page-title-main">Crotonaldehyde</span> Chemical compound

Crotonaldehyde is a chemical compound with the formula CH3CH=CHCHO. The compound is usually sold as a mixture of the E- and Z-isomers, which differ with respect to the relative position of the methyl and formyl groups. The E-isomer is more common (data given in Table is for the E-isomer). This lachrymatory liquid is moderately soluble in water and miscible in organic solvents. As an unsaturated aldehyde, crotonaldehyde is a versatile intermediate in organic synthesis. It occurs in a variety of foodstuffs, e.g. soybean oils.

<span class="mw-page-title-main">1,2-Dichlorobenzene</span> Chemical compound

1,2-Dichlorobenzene, or orthodichlorobenzene (ODCB), is an organic compound with the formula C6H4Cl2. This colourless liquid is poorly soluble in water but miscible with most organic solvents. It is a derivative of benzene, consisting of two adjacent chlorine atoms.

<i>n</i>-Butylamine Chemical compound

n-Butylamine is an organic compound (specifically, an amine) with the formula CH3(CH2)3NH2. This colourless liquid is one of the four isomeric amines of butane, the others being sec-butylamine, tert-butylamine, and isobutylamine. It is a liquid having the fishy, ammonia-like odor common to amines. The liquid acquires a yellow color upon storage in air. It is soluble in all organic solvents. Its vapours are heavier than air and it produces toxic oxides of nitrogen during combustion.

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<span class="mw-page-title-main">Demeton</span> Chemical compound

Demeton, sold as an amber oily liquid with a sulphur like odour under the name Systox, is an organophosphate derivative causing irritability and shortness of breath to individuals repeatedly exposed. It was used as a phosphorothioate insecticide and acaricide and has the chemical formula C8H19O3PS2. Although it was previously used as an insecticide, it is now largely obsolete due to its relatively high toxicity to humans. Demeton consists of two components, demeton-S and demeton-O in a ratio of approximately 2:1 respectively. The chemical structure of demeton is closely related to military nerve agents such as VX and a derivative with one of the ethoxy groups replaced by methyl was investigated by both the US and Soviet chemical-weapons programs under the names V.sub.X and GD-7.

<span class="mw-page-title-main">Phorate</span> Chemical compound

Phorate is an organophosphate used as an insecticide and acaricide.

Methacrylonitrile, MeAN in short, is a chemical compound that is an unsaturated aliphatic nitrile, widely used in the preparation of homopolymers, copolymers, elastomers, and plastics and as a chemical intermediate in the preparation of acids, amides, amines, esters, and other nitriles. MeAN is also used as a replacement for acrylonitrile in the manufacture of an acrylonitrile/butadiene/styrene-like polymer. It is a clear and colorless liquid, that has a bitter almond smell.

<span class="mw-page-title-main">EPN (insecticide)</span> Chemical compound

EPN is an insecticide of the phosphonothioate class. It is used against pests such as European corn borer, rice stem borer, bollworm, tobacco budworm, and boll weevil.

<span class="mw-page-title-main">Tebufenpyrad</span> Chemical compound

Tebufenpyrad is an insecticide and acaricide widely used in greenhouses. It is a white solid chemical with a slight aromatic smell. It is soluble in water and also in organic solvents.

References

  1. 1 2 3 4 5 6 NIOSH Pocket Guide to Chemical Hazards. "#0311". National Institute for Occupational Safety and Health (NIOSH).
  2. 1 2 3 "Heptachlor". Immediately Dangerous to Life or Health Concentrations (IDLH). National Institute for Occupational Safety and Health (NIOSH). 4 December 2014. Retrieved 27 March 2015.
  3. ↑ Robert L. Metcalf "Insect Control" in Ullmann’s Encyclopedia of Industrial Chemistry, Wiley-VCH, Weinheim, 2002. doi : 10.1002/14356007.a14_263
  4. 1 2 3 4 Plimmer, J. R., ed. (2003). The Encyclopedia of Agrochemicals, Volume 3. New York: John Wiley & Sons.
  5. 1 2 California Environmental Protection Agency (1999). Public Health Goal for Heptachlor and Heptachlor Epoxide In Drinking Water - Office of Environment Health Hazard Assessment, California Environmental Protection Agency. "Archived copy" (PDF). Archived from the original (PDF) on 2009-05-04. Retrieved 2013-12-19.{{cite web}}: CS1 maint: archived copy as title (link) (retrieved on April 04, 2009).
  6. 1 2 3 ATSDR, (2007). Heptachlor and Heptachlor Epoxide - Fact Sheet .
  7. ↑ The Foundation for Global Action on Persistent Organic Pollutants: A United States Perspective. DIANE Publishing. 2002. ISBN   978-1-4289-0041-7.
  8. ↑ Harmon, Katherine 2010 New Mass-Screening Method Finds Additional Environmental Risks for Diabetes. Scientific American, May 21, 2010.
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