Fenvalerate General

Pyrethroid Esters of Benzene Acetate. These insecticides have more extensive stmctural optimization in both acid and alcohol moieties. Fenvalerate [51630-58-17, a-cyano-(3-phenoxyphenyl)methyl (+)-(2R,5)"Ct"isoprop5i-4-chlorophenylacetate (24) d 1.17, vp 1.4 p.Pa at 25°C), a mixture of four isomers, is soluble in water to 0.3 mg/L The rat oral LD q is 450 mg/kg. Esfenvalerate [66230-04-4] is the (+)-2-(i, 5)-isomer (mp 59°C). The rat LD qS are 75, 458 (oral), and the rabbit dermal LD q is 2000 mg/kg. These pyrethroids are widely used general-purpose insecticides for field, vegetable, and fmit crops. 

In biological samples, fenvalerate neither persists for lengthy periods nor is readily accumulated (Smith and Stratton 1986 Cooper 1991). In general, fenvalerate is rapidly (i.e., Tb 1/2 of 6 to 14 h) excreted by amphibians, birds, and mammals has low persistence in various reptiles, terrestrial... 

In general, these authorities agree that pyrethroids containing both a halogenated acid esterified with the a-cyano-3-phenoxybenzyl alcohol — such as fenvalerate, deltamethrin, and cyper-... 

Four datasets are taken as examples for discussion, those for chlorothalonil. Dataset B (a general fenvalerate data set). 

Pyrethroids, due to their high insecticidal activity and low mammalian toxicity (1), have been the subject of much synthetic effort (1-2). Most of the commercially available synthetic pyrethroids are generally related in that they contain the same meta-phenoxvbenzvl alcohol, or some close derivative thereof in the molecule, two examples being permethrin and fenvalerate. 

This symptom was hrst reported in 1948 on Andrena flavipes which was repelled by a DDT apphcation [16]. Further assessments were those on M. rotundata [23] and B. terrestris [25], which reacted negatively to residues of the three pyrethroids fenvalerate, deltamethrin, and lambda-cyhalothrin. Visits of plants treated with pyrethroids by M. rotundata females were reduced by 50 percent compared to control. Generally, bees approached the flowers but did not touch them, or if they did, the contact was very brief. This repellency lasted more than 1 hour with fenvalerate and more than 3 hours with deltamethrin [23]. 

In general, fenvalerate administered to mammals was rapidly eliminated and had little tendency to accumulate in tissues. Fenvalerate killed sensitive species of mammals at a brain injection concentration of 1.0 mg/kg FW brain (equivalent to 14.0 xg/kg body weight = BW), an intraperitoneal injection concentration of 3.9 mg/kg BW, acute oral doses of 50.0 to... 

A supplementary list was also drawn up for selective agents with particular rather than general uses dimethoate 13.35), diazinon 13.28), dicofol 6.43), chlorpyrifos 13.32), endosulfan 6.48), lindane 6.45), phosphamidon 13.33), methomyl 13.41), camphechlor (see p. 240), and three pyrethroids deca-methrin 6.54a), permethrin 6.54b), and fenvalerate 6.55) (Metcalf, 1980). 

In the last century, the development of organophosphorus, carbamate, and organochloride insecticides was followed by synthetic pyrethroids. As a result, pyrethroids are now used frequently in the domestic milieu. Pyrethroid insecticides are synthetically derived from the molecular structure or sharing the same mechanism of action of natural pyrethrins that have broader spectmm of activity, more stability, and residual activity (persists longer than that of natural pyrethrins) and include the following allethrin, cyfluthrin, cyhalothrin, cypermethrin, deltamethrin, fenvalerate, flumethrin, fluvalinate, tau-fluvalinate, and permethrin (see structure in Fig. 137.2). They are lipophilic compounds and generally of low acute oral toxicity to mammals but are very toxic to aquatic organisms. When synthetic pyrethroids are administered to mammals parenterally, the synthetic pyrethroids are neurotoxic. 

Pyrethroid insecticides are generally classified into one of two large groups on the basis of the central neurotoxic syndrome that they produce [5, 6]. Type I pyrethroids are esters of chrysanthemic acid and an alcohol, having a furan ring and terminal side chain moieties, and absence of a cyano moiety. Allethrin was the first pyrethroid identified in 1949. Allethrin and other pyrethroids such as phenothrin and permethrin with the basic cyclopropane carboxylic ester structure are type I pyrethroids. The insecticidal activity of these synthetic pyrethroids was enhanced further by the addition of a cyano group to give ot-cyano type II pyrethroids such as deltamethrin, fenvalerate, cyfluthrin, cyhalothrin, and lambda-cyhalothrin (Fig. 137.2). 

Synthetic analogs of the pyrethrins, pyrethroids, have been widely produced as insecticides during recent years. The first of these was allethrin, and another common example is fenvalerate (see structural formulas in Figure 4.6). Other examples of insecticidal pyrethroids that have water pollution potential include cypermethrin and deltamethrin. Because of the ways that they are applied and their biodegradabilities, these substances generally are not found to be significant water pollutants. 

Name (General Name) Fenvalerate (Code No.) S-S602 (CA Reg. No.) 51630-58-1... 

The molecular weight of most agrochemicals provides a simple generalization of the size and complexity of the molecules that are commercially employed as pesticides. The common names of some extensively used pesticides are followed by their molecular weights in parentheses DDT (354.5), 2,4-D (249), cap tan (300.6), malathion (330.4), atrazine (215.7), carbaryl (201.2), dicamba (221), glyphosphate—salt (228.2), fenvalerate... 

There are two general classes of synthetic pyrethroids, the halovinylcyclopropane types and the open chain types. Permethrin was the first of the halovinylcyclopropane type and fenvalerate was the first of the open chain type that had outstanding properties. 

---