Pesticides, chlorinated stability

OC are man-made chemical substances that encompass a wide range of compounds with different structures and applications. They are known for their high chemical stability, which stems from their large proportion of halogen substituents, either chlorine, bromine or others. Some of them were synthesised for use as pesticides and others for industrial applications. 

Epichlorohydrin is usually prepared from propene and is mainly used in the manufacture of glycerol and epoxy resins. It is also used in the manufacture of elastomers, glycidyl ethers, cross-linked food starch, surfactants, plasticizers, dyestuffs, pharmaceutical products, oil emulsifiers, lubricants, and adhesives as a solvent for resins, gums, cellulose, esters, paints, and lacquers and as a stabilizer in chlorine-containing substances such as rubber, pesticide formulations, and solvents. 

Of the several classes of synthetic insecticides, the chlorinated hydrocarbon (CH) and organophosphate (OP) insecticides have the greatest psychiatric significance [Pesticides and Neurological Diseases 1982 Ecobichon 1996). The CH insecticides, also called organochlorine insecticides, include three chemical classes di-chlorodiphenyltrichloroethane (DDT), cyclodienes (aldrin, dieldrin, heptachlor, chlordane, endosulfan), and chlorinated benzene and cyclohexanes (lindane) (Ecobichon 1996). Their ban in the United States and Europe resulted from their high chemical stability and lipid solubility that allowed environmental persistence and magnification in the food chain (Ecobichon 1996 Kaloyanova and El Batawi 1991). 

A second group of important POP s is represented by chlorinated pesticides. Major attention was attributed to the environmental occurrence and fate of DDT and its numerous metabolites. As a result a comprehensive knowledge about the major properties with respect to environmental considerations (environmental stability, toxicological effects, transport processes including its global distribution etc.) exists. For instance the information on the degradation pathway under aerobic as well as under anaerobic conditions is nearly complete as illustrated in Fig. 3. 

Method performance in air analysis involves terms such as accuracy, storage stability, capacity, sampling rate, recovery, and sensitivity. To evaluate the performance of a developed method, certified reference materials for particulate matter, such as urban dust SRM 1649a particulate matter from NIST (Gaithersburg, MD, USA) can be purchased. In addition, a standard reference material has been recently developed for the determination of organic compounds in house dust the SRM 2585 is intended for using in method validation for the analysis of PAHs, PCBs, chlorinated pesticides, and PBDEs (Poster et al. 2007). 

Our laboratory investigations indicated that the purity of the dinitro compounds prepared by homogeneous or direct nitration would not exceed 90 2%. On the other hand, achieving product purity between 95 and 98% using the traditional sulfonation process followed by nitration was no problem. Since the pesticide DNBP was required to be at least 95% pure, the direct nitration process could not be adopted for that product. In this particular case, the client needed approximately a 22% solution of DNOC in styrene. Product testing by the user indicated that the DNOC purity requirement for the styrene monomer stabilizer solution was not critical as long as it exceeded 90%. The final formulation contained 22 to 24% DNOC in styrene. The product met the specifications, was tested by the user, and performed well in field tests. The product also had no chlorinated compounds present even in trace amounts as specified by the user. 

The stabilizing aromatic eiTect explains why the addition reactions characteristic of alkenes do not occnr with aromatics componnds. Addition of chlorine to benzene requires special conditions. The reaction can proceed only by irradiation of the mixture of benzene and chlorine with ultraviolet hght. The result of this reaction is a mixture of isomers of hexachlorocyclohexane. Some of these isomers known under the commercial name HCH are used as pesticides. 

Uses Emollient, solvent, emulsion stabilizer for cosmetics, topical pharmaceuticals solubilizer, coupling agent for perfumes, colors, flavors, sunscreen compds. solvent for sprayed org. pesticides plasticizer and stabilizer in vinyl copolymers made from PVAc and PVC defoamer in PVAc emulsions Features Stable base produces sprayable oils which spread well, have good adherence, and are not readily removed by rainfall Properties Yel. cl. liq., mild odor sol. in most org. soivs. such as alcohols, ketones, esters, glycol ethers, veg. oil, min. oil, aliphatic, aromatic, chlorinated hydrocarbons disp. in glycols, triols, polyols m.w. 258 (theorel) sp.gr. 0.905 0.01 dens. 7.45 Ib/gal f.p. 10 C acid no. 5 max. iodine no. 1 max. sapon no. 225-240 flash pt. (OC) 160 C min. pH 7.0 (10% disp.)... 

Uses Corrosion inhibitor, hydrotrope dry cleaning detergent emulsifier for pesticides, emulsion polymerization, cleaning formulations latex stabilizer and adhesion promoter in emulsion polymerization Features Stable in strongly alkaline and electrolytic sol ns. and at high temps. Properties Lt. amber vise, liq. sol. in alcohols, glycol ethers, aromatic and aliphatic hydrocarbons, chlorinated soivs. disp. in water sp.gr. 1.12 dens. 9.32 Ib/gal pH 2.0-2.5 (1% aq.) 100% act. 

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