Cypermethrin - (R, S) -a-cyano-3-phenoxybenzyl (1RS) -cis-trans-3- (2,2-dichlorvinyl) -2,2-dimethylcyclopropanecarboxylate is a second generation pyrethroid . Despite the fact that cypermethrin appeared on the world market in the early 1970s, it is this compound that is currently the most widely consumed insecticide in the world (mainly for agriculture) .
| Cypermethrin | |
|---|---|
| Are common | |
| Chem. formula | C₂₂H₁₉Cl₂NO₃ |
| Classification | |
| Reg. CAS number | |
| PubChem | |
| Reg. EINECS number | |
| Smiles | |
| Inchi | |
| Chebi | |
| ChemSpider | |
| Security | |
| LD 50 | 250-300 mg / kg |
| Toxicity | medium toxic |
Content
Physical Properties
Viscous colorless liquid with crystals with a faint odor. It is practically insoluble in water (solubility at 20 ° C 0.009 mg / l [1] ), it is highly soluble in most organic solvents - ethyl acetate , acetone , methanol , hexane .
Chemical Structure
The cypermethrin molecule contains 3 asymmetric carbon atoms, that is, 2³ = 8 isomers are possible for it. Each of these isomers exhibits insectoacaricidal properties to one degree or another - one of the isomers is more active against lepidopteran insects, the other against beetles, etc. Thus, the activity of marketed cypermethrin, as well as the specificity of this activity, strongly depends on its isomeric composition, and therefore, on the world market, various isomeric mixtures of cypermethrin are labeled differently.
Cypermethrin is a racemic mixture of the cis- and trans-isomers of cypermethrin; their ratio varies approximately from 40:60 to 50:50. Technical cypermethrin is a viscous yellow or light brown liquid with a honey consistency.
Alpha cypermethrin is a racemic mixture containing only the cis isomers of cypermethrin - basically, it is (1R-cis) S and (1S-cis) R isomers.
Beta-cypermethrin (Kinmix) is a racemic mixture of cis and trans isomers of cypermethrin with a predominance of trans isomers (cis / trans ratio) of about 40:60. White crystalline powder.
Theta Cypermethrin - In contrast to alpha cypermethrin, theta cypermethrin contains only trans isomers with a predominance of (1R-trans) S + (1S-trans) R. It is a white or almost white crystalline powder.
Zeta-Cypermethrin (zeta-Cypermethrin, Fury) - it contains both cis and trans isomers, but unlike the above varieties, zeta cypermethrin is optically active - it contains the 4 most active cypermethrin isomers with S-configuration cyano groups.
The isomeric composition of commercial cypermethrin may depend on either the specific chemical synthesis scheme that forms the basis of the industrial method for its preparation, or on some technology details, purification methods, etc. In addition, the final product can be artificially enriched with some of the most active isomers, while less active isomers can be returned to the process for the purpose of racemization and subsequent recycling.
Cypermethrin can be considered not only the most common, but also the most typical representative of synthetic pyrethroids, which, as it were, has incorporated all the characteristic advantages and disadvantages of this class of insecticides.
Insect Effect
Like all pyrethroids , cypermethrin easily penetrates through the covers of insects, and disrupts the functioning of the nervous system, causing paralysis and death. It does not have a systemic effect (i.e., does not enter the vascular system of plants), but remains for a long time on the treated surfaces (20-30 days), since it is sufficiently resistant to high temperatures and ultraviolet rays. The period of protective action is 10-15 days. It also has a repellent (deterrent) property.
It is used against wheat pests (cereal aphids, breadworms, drunks, fleas, bread thrips, bug bugs , bread bugs, cereal gall midges , ground beetles , in- stem flies ), barley (in- stem flies, leech , bread fleas ( scoop ), , corn moth), flax flax (flax fleas), sunflower (meadow moth), grapes ( leaf moths ), potatoes ( Colorado potato beetle , potato cow ), cucumbers and tomatoes of protected ground ( whitefly , aphids , thrips ). They are also used for the destruction of flightless domestic insects ( bed bugs , cockroaches of various species, ants and fleas ), and for processing the landing sites of flies .
Environmental toxicity and sustainability
Highly toxic to bees (LD50 contact - 20 ng / individual) and other beneficial insects, fish and small aquatic crustaceans (daphnia, shrimp). It is medium toxic for mammals ( LD50 for rats 250-300 mg / kg), low toxicity for birds (LD50> 10000 mg / kg for mallard duck), moderately dangerous for earthworms [1] .
Under the influence of sunlight, oxygen and moisture, cypermethrin decomposes into neutral substances within a month after application. In loamy and sandy loamy soil it lasts 2-4 weeks, in clayey soil - up to 10 weeks [2] .