Insecticides, halogenated

Cinnamyl—sesamol ethers, eg (35), are useful as insect chemosterilants (111). 3,4-Methylenedioxyphenyl-3-halo-2-propynyl ethers (36, X = halogen) are synergists for carbamate insecticides (112). HaloaLkyl or haloalkenyl ethers, eg (37), show acaricidal and insect juvenile hormone activity (113). The first total synthesis of gibbereUic acid was from 2-methoxy-6-aLkoxyethyl-l,4-benzoquinone, a derivative of hydroxyhydroquinone (114). 

Halogen Substituents. Halogen functional groups are readily replaced by nucleophiles, eg, hydroxide ion, especially when they ate attached at the a- or y-position of the pyridine ting. This reaction has been exploited in the synthesis of the insecticide chlorpyrifos [2921-88-2J (43) (42), and the insecticide tiiclopyi [55335-06-3] (44) (14,43). 2,3,5,6-Tetiachloiopyiidine [2402-79-1] reacts with caustic to form the hydioxylated material [6515-38-4], which then can be used to form (44) and (43). 

Halogenation. Halogens and halogen acids add readily to the unsaturated carbon linkages of the cyclopentadiene molecule. By such additions a series of halogenated derivatives range, in the case of the chloride, from 3-chlotocydopentene to tetrachlorocyclopentane. Of all the possible chloto derivatives of CPD, only hexachlorocyclopentadiene [77-47-4] ever reached commercial status. It was used as an insecticide, but this use has been discontinued because of its toxicity (see Chlorocarbons and chlorohydrocarbons, toxic aromatics). It can be prepared by a Hquid phase chlorination of CPD below 50°C (29). 

Amongst synthetic quinoxalines, numerous types of biological activity have been reported. 5,6,7,8-Tetrachloroquinoxaline (132) and related halogenated derivatives have found use in fungicidal formulations. Phosphoric esters of 6-hydroxyquinoxaline (133) have found use in insecticidal preparations, and phosphoric ester derivatives of 2-hydroxyquinoxalines, such as (134), function as anthelmintics. 

Halogen-containing substances e. g. chlorine-containing insecticides [1, 7] such as aldrin, dieldrin, DDT, perthane,... 

In the case of halogen-containing substances (e. g. insecticides) the chromatograms are moistened by spraying with water after treatment with the reagent and then exposed to unfiltered UV light for ca. 1 min [1, 7] or to sunlight for 30 min [8]. 

During a decanting operation of chloropicrin/propargyl bromide insecticide mixture, a very violent detonation took place when it came into contact with a pump that heated up accidentally. Note that this risk seems rather obvious since propargyl bromide (see NFRA stability code 4 see also halogen derivatives ) is as unstable as chloropicrin. 

Two new insect toxicants, aldrin and dieldrin, provide new halogenated insect toxicants with an extremely high order of toxicity toward insects, combined, for the first time, with complete stability to alkalies. Under all the usual conditions of use these new toxicants are also stable to acids. Data illustrate the order of magnitude of the insecticidal activity of these materials and their utility. Aldrin is a relatively nonresidual material, in contrast to dieldrin which, because of its high persistence, exhibits prolonged residual activity. 

Because the results obtained reflect the presence, not only of the insecticide in question, but also of any of its decomposition products or other organic compounds containing halogen, confirmatory evidence of the identity and amount of the residues was desired, Therefore, studies to correlate the results of organic-chlorine determinations with insecticidal activity were undertaken. 

Dining the blending of the two insecticides (endrin is a halogenated polycyclic epoxide) into a petroleum solvent, an unexpected exothermic reaction occurred which vaporised some solvent and led to a vapour-air explosion. Faulty agitation was suspected. 

There is only one simple anion commonly found in soil, and that is chloride (Cl ). Chloride is an essential nutrient for plants but is typically present in sufficiently high concentrations that deficiencies are never observed. If other halogens are present, they will also be present as simple anions. Most soils do contain small amounts of bromide as the second most common simple anion. In some cases, significant levels of fluoride and iodide may be present, although this is rare. These anions are generally soluble in water and tend to exist as the simple anion. However, they can combine with other components and exist as other species. For instance, halogens are present in organic compounds such as solvents, insecticides, and herbicides, which can be soil contaminants. There are also other nonionic species of these elements that may be present [20],... 

Von Oettingen WF. 1955. The halogenated aliphatic, olefinic, cyclic, aromatic, and aliphatic-aromatic hydrocarbons including the halogenated insecticides, their toxicity and potential dangers. Washington, DC U.S. Public Health Service. PHS Publication No. 414, 15-28. 

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