Acidic pesticides, properties

Uses Emulsiferfor aromatic soivs., fats, oils, fatty acids, pesticides Properties Liq. HLB 9.6 99% cone. 

An extensive pesticide properties database was compiled, which includes six physical properties, ie, solubiUty, half-life, soil sorption, vapor pressure, acid pR and base pR for about 240 compounds (4). Because not all of the properties have been measured for all pesticides, some values had to be estimated. By early 1995, the Agricultural Research Service (ARS) had developed a computerized pesticide property database containing 17 physical properties for 330 pesticide compounds. The primary user of these data has been the USDA s Natural Resources Conservation Service (formerly the Soil Conservation Service) for leaching models to advise farmers on any combination of soil and pesticide properties that could potentially lead to substantial groundwater contamination. 

Table 10.2. Structure and Properties of Several Acidic Pesticides...

Hydroxy-l,2,4-thiadiazoles readily form esters with phosphoric acid and its various analogs. Because of the pesticidal properties of these organo-phosphorus compounds, and their reported relatively low toxicity to warmblooded animals, a large volume of preparative work has been undertaken. The patent literature exemplifies almost the full range of possible phosphoric and phosphonic acid derivatives, and their thio analogs. For their production, a hydroxy-1,2,4-thiadiazole is condensed with the phosphoro- or phosphono-chloridic ester (426 or 429), in the presence of a base.332-336 Alternatively, a halogeno-1,2,4-thiadiazole is allowed to react with the appropriate free acid (424 or 427).337-341 The use of mercapto-l,2,4-thiadiazoles, or of the... 

Chemical properties of some acidic pesticides are shown in Table IV. The chemicals are all herbicides except for TIBA, DMSA, and MH, which are plant growth regulators. They range in acid strengths from the strong acid TCA to the relatively weak acid MCPB. The first five compounds in Table IV are members of the chloro-phenoxy acids. The next five are substituted benzoic acids. Compounds starting with fenac and ending with MH are assorted acids, and the last four compounds are substituted phenols. 

Basic substances, listed in annex IB, without any pesticidal property, which are necessary, e.g., as diluents typical examples are carbon dioxide, nitrogen, ethanol, isopropanol, acetic acid, and kieselguhr. 

To use a more sophisticated example, we can look to the products of the neem tree (Azadirzchta indica), a tropical plant that is known for its pesticidal properties. The seed of this tree is abundant with limonoids and simple terpenoids that are responsible for its biological activity. One particular limonoid found in the seed is Azadirachtin (2.134). The bioactivity of Azadirachtin potentially leads to a wide range of applications in herbal medicine and healthcare products for the treatment of malaria and tuberculosis and in anti-worm, clotting, and blood-detoxification preparations. These uses of Azadirachtin as a biopesticide or herbal medicine is limited due to solubility constraints in water and its instability as a result of its propensity to undergo complicated, irreversible rearrangements under acidic, basic and photolytic conditions. Consequently, there has been much research in the structural modification of Azadirachtin to overcome its solubility constraints to increase stability. This process normally involves many protection and deprotection synthetic steps and chromatographic separations. 

Uses Wetting agent, dispersant for metal and acid cleaners, pesticides Properties Liq. HUB 13.0 99% min. cone. 

The zinc. salts of these acids are extensively used as additives to lubricating oils to improve their extreme-pressure properties. The compounds also act as antioxidants, corrosion inhibitors and detergents. Short-chain dialkyl dithiophosphates and their sodium and ammonium salts are used as flotation agents for zinc and lead sulfide ores. The methyl and ethyl derivatives (RO)2P(S)SH and (RO)2P(S)CI are of particular interest in the large-scale manufacture of pesticides such as parathion, malathion, dimethylparathion, etc. For example parathion. which first went into production as an insecticide in Germany in 1947. is made by the following reaction sequence ... 

Besides trace metals, adsorptive stripping voltammetry has been shown to be highly suitable for measuring organic compounds (including cardiac or anticancer drugs, nucleic acids, vitamins, and pesticides) that exhibit surface-active properties. 

There are a large number of literature references that refer the use of SPE cartridges for the extraction of pesticides from water. There are several comprehensive reviews of the use of SPE, including that by Soriano et al. who discussed the advantages and limitations of a number of sorbents for the analysis of carbamates. Hennion reviewed the properties and uses of carbon based materials for extraction of a wide multiclass range of pesticides. Thorstensen et al. described the use of a high-capacity cross-linked polystyrene-based polymer for the SPE of phenoxy acids and bentazone, and Tanabe et al reported the use of a styrene-divinylbenzene copolymer for the determination of 90 pesticides and related compounds in river water. SPE cartridges are also widely used for the cleanup of solvent extracts, as described below. 

A polyethylene-coated (PEE) silica column was used with water-methanol eluents to achieve the separation and retention of 27 pesticides.40 The retention times of 33 commercial pesticides were determined on an octadecyl (ODS)-derivatized alumina column using water-methanol eluents and compared with retention properties on an ODS-silica column packing.41 More recently, RP-HPLC was used in combination with diode array detection for the identification and quantification of 77 pesticides (acidic, basic, and neutral) in groundwater samples.42... 

The transformation and metabolism products of pesticides in plants may not only be of acute toxicity, but also may have other properties. Phosmet, for example, transforms into phthalimide and phthalic acid, teratogenic substances [21]. 

Esters represent an important class of chemical compounds with applications as solvents, plasticizers, flavors and fragrances, pesticides, medicinals, surfactants, chemical intermediates, and monomers for resins. Recently, esters of amino acids have attracted attention regarding their use as biobased surfactants with excellent adsorption and aggregation properties, low toxicity, and broad biological activity. 

Another compartmental partitioning issue of major consequence for pesticides is the dissolved versus adsorbed fraction in an aqueous environment. Carter and Suffet (16) present measurements of binding of pesticides to dissolved fulvic acids that-will provide inputs to compartment models. Data from laboratory measurements used in compartment models can often bypass costly field experiments in the screening stage. Thomas, Spillner and Takahashi (1 7) have related the soil mobility of alachlor, butylate and metachlor to physicochemical properties of these compounds. 

A possible source of groundwater contamination, which has up to now almost been neglected, is associated with the introduction of surfactants into soils as pesticide additives (Table 6.7.3). Non-ionic surfactants composed of alcohols and fatty acids are most widely recommended as adjuvants to facilitate and enhance the absorbing, emulsifying, dispersing, wetting and penetrating properties of pesticides. Other pesticide adjuvants are silicone-based surfactants,... 

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