theta-Cypermethrin

The Uses of theta-Cypermethrin

Theta-cypermethrin is used for public health and animal pest control.

Definition

ChEBI: (1R)-trans-(alphaS)-cypermethrin is a cyclopropanecarboxylate ester. It is an enantiomer of a (1S)-trans-(alphaR)-cypermethrin.

Metabolic pathway

Theta-cypermethrin is composed of two of the four trans-cypermethrin isomers of cypermethrin (1RtransaS and 1StransaR). The fate of these two isomers (separately) has been reported for soils. Metabolite analysis was conducted in enough detail to indicate that the fate of the components was very similar to their fate when presented to biological systems as part of cypermethrin. Thus reference can be made to the cypermethrin entry for details. The structure and Scheme numbering used below refers to the cypermethrin entry.

Degradation

Theta-cypermethrin is stable as a solid but it is readily hydrolysed in alkaline solution. Its half-lives at pH values 3,7 and 9 (25 °C) were 50,20 and 10 days (PM). By analogy with cypermethrin, the rate-determining step in dilute solution is nucleophilic attack by OH^-. Half-lives of transcypermethrin in river water and sea water at 25 °C were 5 and 7 days, respectively. Major products were 3-(2,2-dichlorovinyl)-2,2-dimethylcyclopropanecarboxylic acid (2, DCVA), 3-phenoxybenzaldehyde (9, 3PBAl) and a-carbamoyl-3-phenoxybenzyl 3-(2,2-dichlorovinyl)-2,2- dimethylcyclopropanecarboxylate (the amide 3); minor products were the a-carboxy analogue of 3 (4) and 3-phenoxybenzoic acid (10,3PBA) (see cypermethrin, Schemes la and 1b).
Photodecomposition would be expected to be similar to that of cypermethrin.