Tetramethrin

Description

Form: Colorless crystals with slight pyrethrum-like odor

Chemical properties

white crystals or powder

The Uses of Tetramethrin

Tetramethrin is used to control flies, wasps, cockroaches and other insects in public health, home and garden situations.

The Uses of Tetramethrin

Tetramethrin is a synthetic pyrethroid pesticide used in large-scale commercial agricultural applications as well as in consumer products for domestic purposes.

The Uses of Tetramethrin

Insecticide.

Definition

ChEBI: Tetramethrin is a phthalimide insecticide, a member of maleimides and a cyclopropanecarboxylate ester. It has a role as a pyrethroid ester insecticide. It is functionally related to a chrysanthemic acid.

General Description

Colorless crystals with slight odor. Non corrosive. Used as an insecticide.

Air & Water Reactions

Hydrolysis occurs with strong acid or base.

Reactivity Profile

A pyrethroid. Tetramethrin is an ester and nitrile. Esters react with acids to liberate heat along with alcohols and acids. Strong oxidizing acids may cause a vigorous reaction that is sufficiently exothermic to ignite the reaction products. Heat is also generated by the interaction of esters with caustic solutions. Flammable hydrogen is generated by mixing esters with alkali metals and hydrides.

Agricultural Uses

Insecticide: Tetramethrin is often formulated as an aerosol and used primarily for indoor pest control or in mosquito coils. It is also used in shampoos to control fleas and ticks on pets. It is often formulated with other insecticides and synergists. Not approved for use in EU countries. Registered for use in the U.S.

Trade name

FMC 9260®; ENT-27339; EVERCIDE INTERMEDIATE® 2265 (tetramethrin + fenvalerate); MULTICIDE®; NEO-PYNAMIN®; NEOPYNAMINE®; NEOPYNAMIN FORTE®; NIAGARA®-9260; NIA®- 9260; PHTHALTHRIN®; SP-1103; SUMITOMO® SP-1103

Metabolic pathway

Tetramethrin was the second synthetic pyrethroid to be produced commercially (1964). The compound has a rapid knock-down action and a reasonable killing activity which is enhanced by use with synergists. It is usually used with piperonyl butoxide and in the presence of other insecticides. It has two chiral centres, both in the acid group, and therefore is a 1 RS-cis-trans mixture. A(1R)-rich product containing cis- and trans-isomers in the ratio 20:80 is also used in public health; this is named dtetramethrin. The two products will not be distinguished here because metabolic studies have been performed with various combinations of isomers. Most published information relates to its mode of action in insects and its metabolism in rodents. This is a reflection of its limited outdoor and field use.

Degradation

Tetramethrin is a stable chemical but it is base labile and it is also sensitive to strong acids. It is hydrolysed to (1RS)-cis-trans-2,2-dimethyl-3-(2- methylprop-1-enyl)cyclopropanecarboxylic acid (chrysanthemic acid, 2) and tetrahydrophthalimide (4). It is oxidised by m-chloroperbenzoic acid to form epoxy-tetramethrin (5) which is ring-opened to the diol (6) in dilute aqueous acid (Smith and Casida, 1981). This reaction has been postulated as initiating the opening of the cyclopropane ring with the ultimate formation of CO ₂ in biological systems (see below). Another biomimetic reaction of tetramethrin and its ester cleavage product 4 is Michael addition of thiols to the double bond. Glutathionyl-tetramethrin (7) is formed by incubation of the constituents in buffered aqueous methanol (Smith et al., 1982). Its formation on incubation with mouse liver microsomes is probably non-enzymatic. At the time of this discovery there appeared to be no equivalent reaction in vivo but the more recent discovery of sulfonate metabolites (see below) demonstrates its role.
The chrysanthemic acid esters are very sensitive to photodegradation, being subject to ring-opening initiated by the formation of epoxides such as 5 (Ruzo et al., 1982) as described under bioallethrin and phenothrin. Isomerisation was observed only in de-oxygenated benzene solution because photo-oxidative degradation predominated under most conditions. Many products were seen in oxygenated benzene solution and in a thin film in sunlight.
These chemical and photochemical reactions are summarised in Scheme 1.

Toxicity evaluation

Acute oral LD₅₀ for rats: >5,000 mg/kg