Carbaryl (1-naphthyl methylcarbamate) is a chemical in the
carbamate family used chiefly as an
insecticide. It is a white crystalline solid previously sold under the brand name Sevin, which was a trademark of the
Bayer Company. The Sevin trademark has since been acquired by
GardenTech, which has eliminated carbaryl from most Sevin formulations.
Union Carbide
Union Carbide Corporation is an American chemical corporation wholly owned subsidiary (since February 6, 2001) by Dow Chemical Company. Union Carbide produces chemicals and polymers that undergo one or more further conversions by customers befo ...
discovered carbaryl and introduced it commercially in 1958. Bayer purchased Aventis CropScience in 2002, a company that included Union Carbide pesticide operations. Carbaryl was the third-most-used insecticide in the United States for home
gardens
A garden is a planned space, usually outdoors, set aside for the cultivation, display, and enjoyment of plants and other forms of nature. The single feature identifying even the wildest wild garden is ''control''. The garden can incorporate bot ...
, commercial agriculture, and forestry and rangeland protection. As a
veterinary
Veterinary medicine is the branch of medicine that deals with the prevention, management, diagnosis, and treatment of disease, disorder, and injury in animals. Along with this, it deals with animal rearing, husbandry, breeding, research on nutri ...
drug, it is known as carbaril (
INN
Inns are generally establishments or buildings where travelers can seek lodging, and usually, food and drink. Inns are typically located in the country or along a highway; before the advent of motorized transportation they also provided accommo ...
).
Production
Carbaryl is often inexpensively produced by direct reaction of
methyl isocyanate
Methyl isocyanate (MIC) is an organic compound with the molecular formula CH3NCO. Synonyms are isocyanatomethane and methyl carbylamine. Methyl isocyanate is an intermediate chemical in the production of carbamate pesticides (such as carbaryl, ...
with
1-naphthol
1-Naphthol, or α-naphthol, is a fluorescent organic compound with the formula . It is a white solid. It is an isomer of 2-naphthol differing by the location of the hydroxyl group on the naphthalene ring. The naphthols are naphthalene homolog ...
.
:C
10H
7OH + CH
3NCO → C
10H
7OC(O)NHCH
3
Alternatively, 1-naphthol can be treated with excess
phosgene to produce 1-
naphthylchloroformate
Chloroformates are a class of organic compounds with the formula ROC(O)Cl. They are formally esters of chloroformic acid. Most are colorless, volatile liquids that degrade in moist air. A simple example is methyl chloroformate, which is commer ...
, which is then converted to carbaryl by reaction with
methylamine.
[ The former process was carried out in ]Bhopal
Bhopal (; ) is the capital city of the Indian state of Madhya Pradesh and the administrative headquarters of both Bhopal district and Bhopal division. It is known as the ''City of Lakes'' due to its various natural and artificial lakes. It i ...
. In comparison, the latter synthesis uses exactly the same reagents, but in a different sequence. This procedure avoids the potential hazards of methyl isocyanate.
Biochemistry
Carbamate insecticides are slowly reversible inhibitors of the enzyme acetylcholinesterase. They resemble acetylcholine, but the carbamoylated enzyme undergoes the final hydrolysis step very slowly (minutes) compared with the acetylated enzyme generated by acetylcholine (microseconds). They interfere with the cholinergic nervous system and cause death because the effects of the neurotransmitter acetylcholine cannot be terminated by carbamoylated acetylcholinesterase.
Applications
The development of the carbamate insecticides has been called a major breakthrough in pesticides. The carbamates do not have the persistence of chlorinated pesticides. Although toxic to insects, carbaryl is detoxified and eliminated rapidly in vertebrates. It is neither concentrated in fat nor secreted in milk, so is favored for food crops, at least in the US.[Robert L. Metcalf "Insect Control" in Ullmann's ''Encyclopedia of Industrial Chemistry'' Wiley-VCH, Weinheim, 2002. ] It is the active ingredient in Carylderm shampoo used to combat head lice until infestation is eliminated.
Ecology
Carbaryl kills both targeted (e.g., malaria-carrying mosquitos) and beneficial insects (e.g., honeybee
A honey bee (also spelled honeybee) is a eusocial flying insect within the genus ''Apis'' of the bee clade, all native to Afro-Eurasia. After bees spread naturally throughout Africa and Eurasia, humans became responsible for the current cosm ...
s), as well as crustaceans.[Carbaryl General Fact Sheet - National Pesticide Information Center](_blank)
/ref> Because it is highly toxic to zooplankton
Zooplankton are the animal component of the planktonic community ("zoo" comes from the Greek word for ''animal''). Plankton are aquatic organisms that are unable to swim effectively against currents, and consequently drift or are carried along by ...
, the algae they feed on experience blooms. Boone & Bridges 2003 find that larger algae eater
Algae eater or algivore is a common name for any bottom-dwelling or filter-feeding aquatic animal species that specialize in feeding on algae and phytoplanktons. Algae eaters are important for the fishkeeping hobby and many are commonly kept b ...
s such as ''Bufo woodhousii
Woodhouse's toad (''Anaxyrus woodhousii'') is a medium-sized () true toad native to the United States and Mexico. There are three recognized subspecies. ''A. woodhousii'' tends to hybridize with '' Anaxyrus americanus'' where their ranges overla ...
'' benefit from this effect.[ 5.4.1 Taxon-Wide Impacts — Pesticides and Contaminants, and Their Roles in the Decline of Amphibian Populations. Moore, Robin D.; Claude Gascon. pp.111-145.]
It is approved for more than 100 crops in the US. Carbaryl is illegal in the EU and Angola.[Carbaryl Insecticide Hazard Data](_blank)
Safety
Carbaryl is a cholinesterase inhibitor and is toxic to humans. It is classified as a likely human carcinogen
A carcinogen is any substance, radionuclide, or radiation that promotes carcinogenesis (the formation of cancer). This may be due to the ability to damage the genome or to the disruption of cellular metabolic processes. Several radioactive subs ...
by the United States Environmental Protection Agency
The Environmental Protection Agency (EPA) is an independent executive agency of the United States federal government tasked with environmental protection matters. President Richard Nixon proposed the establishment of EPA on July 9, 1970; it ...
(EPA.)Interim Reregistration Eligibility Decision for Carbaryl
, U.S. EPA, June 2003. The oral is 250 to 850 mg/kg for rats and 100 to 650 mg/kg for mice.
Carbaryl can be produced using methyl isocyanate
Methyl isocyanate (MIC) is an organic compound with the molecular formula CH3NCO. Synonyms are isocyanatomethane and methyl carbylamine. Methyl isocyanate is an intermediate chemical in the production of carbamate pesticides (such as carbaryl, ...
(MIC) as an intermediary.[ A leak of MIC used in the production of carbaryl caused the ]Bhopal disaster
The Bhopal disaster, also referred to as the Bhopal gas tragedy, was a chemical accident on the night of 2–3 December 1984 at the Union Carbide India Limited (UCIL) pesticide plant in Bhopal, Madhya Pradesh, India. Considered the world's ...
, the most lethal industrial accident in history.
References
External links
Carbaryl Technical Fact Sheet - National Pesticide Information Center
* ttp://extoxnet.orst.edu/tibs/cholines.htm Cholinesterase Inhibition - Extension Toxicology Networkbr>EPA info
EPA factsheet
*
{{Authority control
Acetylcholinesterase inhibitors
Carbamate insecticides
IARC Group 3 carcinogens
Endocrine disruptors
Naphthol esters
Veterinary drugs
Aromatic carbamates
1-Naphthyl compounds