Carbaryl

Carbaryl

Names
Preferred IUPAC name Naphthalen-1-yl methylcarbamate
Other names Sevin (Generic trademark) α-Naphthyl N-methylcarbamate 1-Naphthyl methylcarbamate
Identifiers
CAS Number	63-25-2 Y
3D model (JSmol)	Interactive image
ChEBI	CHEBI:3390 Y
ChEMBL	ChEMBL46917 Y
ChemSpider	5899 Y
ECHA InfoCard	100.000.505
EC Number	200-555-0
KEGG	D07613 Y
PubChem CID	6129
RTECS number	FC5950000
UNII	R890C8J3N1 Y
UN number	2757
CompTox Dashboard (EPA)	DTXSID9020247
InChI InChI=1S/C12H11NO2/c1-13-12(14)15-11-8-4-6-9-5-2-3-7-10(9)11/h2-8H,1H3,(H,13,14) Y Key: CVXBEEMKQHEXEN-UHFFFAOYSA-N Y InChI=1/C12H11NO2/c1-13-12(14)15-11-8-4-6-9-5-2-3-7-10(9)11/h2-8H,1H3,(H,13,14) Key: CVXBEEMKQHEXEN-UHFFFAOYAZ
SMILES CNC(=O)Oc1c2ccccc2ccc1
Properties
Chemical formula	C12H11NO2
Molar mass	201.225 g·mol−1
Appearance	Colorless crystalline solid
Density	1.2 g/cm3
Melting point	142 °C (288 °F; 415 K)
Boiling point	decomposes
Solubility in water	very low (0.01% at 20°C)
Pharmacology
ATCvet code	QP53AE01 (WHO)
Hazards
GHS labelling:
Pictograms
Signal word	Danger
Hazard statements	H301, H302, H332, H351, H410
Precautionary statements	P201, P202, P261, P264, P270, P271, P273, P281, P301+P310, P301+P312, P304+P312, P304+P340, P308+P313, P312, P321, P330, P391, P405, P501
Flash point	193-202
Lethal dose or concentration (LD, LC):
LD50 (median dose)	710 mg/kg (rabbit, oral) 250 mg/kg (guinea pig, oral) 850 mg/kg (rat, oral) 759 mg/kg (dog, oral) 500 mg/kg (rat, oral) 150 mg/kg (cat, oral) 128 mg/kg (mouse, oral) 230 mg/kg (rat, oral)
NIOSH (US health exposure limits):
PEL (Permissible)	TWA 5 mg/m3
REL (Recommended)	TWA 5 mg/m3
IDLH (Immediate danger)	100 mg/m3
Safety data sheet (SDS)	ICSC 0121
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). N verify (what is YN ?) Infobox references

Spraying carbaryl on pine trees

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 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, commercial agriculture, and forestry and rangeland protection. As a veterinary drug, it is known as carbaril (INN).

Production

Carbaryl is often inexpensively produced by direct reaction of methyl isocyanate with 1-naphthol.

C₁₀H₇OH + CH₃NCO → C₁₀H₇OC(O)NHCH₃

Alternatively, 1-naphthol can be treated with excess phosgene to produce 1-naphthylchloroformate, which is then converted to carbaryl by reaction with methylamine. The former process was carried out in Bhopal. 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. 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., honeybees), as well as crustaceans. Because it is highly toxic to zooplankton, the algae they feed on experience blooms. Boone & Bridges 2003 find that larger algae eaters such as Bufo woodhousii benefit from this effect.

It is approved for more than 100 crops in the US. Carbaryl is illegal in the EU and Angola.

Safety

Carbaryl is a cholinesterase inhibitor and is toxic to humans. It is classified as a likely human carcinogen by the United States Environmental Protection Agency (EPA.) The oral LD₅₀ is 250 to 850 mg/kg for rats and 100 to 650 mg/kg for mice.

Carbaryl can be produced using methyl isocyanate (MIC) as an intermediary. A leak of MIC used in the production of carbaryl caused the Bhopal disaster, the most lethal industrial accident in history.

External links

• Carbaryl Technical Fact Sheet - National Pesticide Information Center
• Carbaryl Pesticide Information Profile - Extension Toxicology Network
• Cholinesterase Inhibition - Extension Toxicology Network
• EPA info
• EPA factsheet
• IPCS (WHO) Health and Safety Guide
• Environmental Health Criteria - WHO
• Exclusive Chemistry Ltd - routes of Sevin synthesis
• CDC - NIOSH Pocket Guide to Chemical Hazards
• Carbaryl in the Pesticide Properties DataBase (PPDB)