Herbicides phenoxyacetic acids

Ditallow dimethyl ammonium Triazine herbicides Phenoxyacetic acid herbicides... 

Triazine herbicides Phenoxyacetic acid herbicides Multiherbicide-insecticide mixtures Humic and fulvic acids Optical whiteners Mixtures of organic 1 1.2.1(n/s) 11.2.2(n/s) 1 l.2.6(n/s) 10.1.3.3(s) ... 

In 1939, the highly efficient contact insecticide DDT (an abbreviation of the technically incorrect name dichlorodiphenyl-trichloroethane) was introduced to the market. Its use, as well as the use of several other organochlorine compounds, spread worldwide in the following years. Important active substances that appeared on the market in the period after World War II include carbamate insecticides and herbicides. Also significant was the discovery of herbicidal phenoxyacetic acids, which represent the first group of the so-caUed hormonally active pesticides. Around the middle of the last century a number of other biologically active substances were discovered, many of which, such as herbicides based on substituted urea, s-triazines (1,3,5-triazines), quaternary ammonium salts or insecticidal synthetic pyrethroids and many others, are still used in many countries around the world. 

Phenoxy acetic acid herbicides Phenoxyacetic acid, MCPA, dichloropro-pmecoprop 2,4-D, 2,4-dichlorophen-oxyacetic acid 2-(2,4,5-trichloro-phenoxy)propionic acid... 

Phenoxyalkanoics. The phenoxyalkanoic herbicide grouping is composed of two subgroups, the phenoxyacetic acids and the phenoxypropionic acids. The phenoxyacetic acid herbicides include some of the first commercially successhil herbicides, eg, 2,4-D. They continue to be widely used for foUar control of broadleaf weeds. The more heavily functionalized phenoxypropionic acid herbicides are relatively new herbicides compared to the phenoxyacetic acids and are used primarily for selective control of grassy weeds in broadleaf crops (2,296,297). 

Phenothiazines 44, 59, 299, 411, 413,416 Phenoxyacetic acid herbicides 260 Phenoxyalkanecarboxylic acid esters 210, 211... 

It was not until 1962 that the first quantitative structure-activity relationship was published by Corwin Hansch and co-workers [13], relating to the herbicidal activity of a series of phenoxyacetic acids ... 

Phenox process, 10 787 Phenoxyacetic acid herbicides, 13 314 Phenoxyacetic acids, 13 50, 304 Phenoxyalkanoic acids, 13 284 Phenoxyalkanoic herbicides,... 

Aliphatic hydrocarbons, triazine, substituted urea type and phenoxyacetic acid types of herbicides, Fluazifop and Fluazifop-butyl herbicides, ethylene diamine tetracetic acid salts in soil, aliphatic and polyaromatic hydrocarbons, phthalate esters, various organosulphur compounds, triazine herbicides, optical whiteners, mixtures of organic compounds and organotin compounds in non-saline sediments, aromatic hydrocarbons, humic and fulvic acids and mixtures of organic compounds in saline sediments and non-ionic surfactants and cobalamin in sludges. 

Conversion to methyl esters followed by gas chromatography has been used to determine phenoxyacetic acid herbicides in sewage sludge [162],... 

It is seen from Table 16.4, for example, that TCA a phenoxyacetic acid type of herbicide has a solubility exceeding 500000pg L 1 while chlorotoluron, a phenyl urea herbicide has a water solubility of 70mg L-1. Thus, due to rainfall over a period of time the concentration of TCA in soil will reduce considerably more rapidly than that of chlorotoluron. 

Other carboxylic acids that have become popular herbicides, though they are not phenoxyacetic acid derivatives, are dicamba and glyphosate or Roundup . Notice that dicamba does have a methoxy group and two chlorines, so it is similar to 2,4-D. Glyphosate is used on cotton and... 

Phenoxyacetic acid herbicides (see Chlorophenoxy herbicides) Phenoxybenzamine hydrochloride... 

Other herbicidal phenoxyacetic and phenoxypropionic acids have some properties similar to those of (2,4-dichlorophenoxy)acetic acid, but often have quite different species selectivity. Some of the differences can be explained on the basis of molecular stability, persistence, or mobility in the toxic form, as well as on the basis of differences in solubility and in absorption through leaves or roots. 

Many synthetic auxins have been produced, including 2,4-dichIoro-phenoxyacetic acid or 2,4-D naphthalene-l-acetic acid and 2,3,6-trichlorobenzoic acid, among others. Used as a herbicide. 2.4-D is described in Herbicides. 

For instance, a 2,4-dichlorophenoxyacetic acid systemic herbicide has been determined by adopting this procedure. 2,4-Dichlorophenol and 2,5-dihydroxyphe-nylacetic acid (also known as homogentisic acid) were used as electroactive competitors and DPV for signal transduction [6]. Likewise, 2-chloro-4-hydroxy-phenoxyacetic acid was applied as the electroactive competitor for detection of the... 

Renberg [169] used an ion exchange technique for the determination of chlorophenols and phenoxyacetic acid herbicides in soil. In this method, the soil extracts are mixed with Sephadex QAE A-25 anion exchanger and the adsorbed materials are then eluted with a suitable solvent. The chlorinated phenols are converted into their methyl ethers and the chlorinated phenoxy acids into their methyl or 2-chloroethyl esters for gas chromatography. 

Gas chromatography has been used extensively for the determination of phenoxyacetic acid-type herbicides in soil extracts (Table 4.9). 

Chau and Terry [397] reported the formation of pentafluorobenzyl derivatives of ten herbicidal acids, including 4-chloro-2-methyl-phenoxyacetic acid [ 396 ]. They found that five hours was an optimum reaction time at ambient temperature with pentafluorobenzyl bromide in the presence of potassium carbonate solution. Bromination [398], nitrification [399] and esterification with halogenated alcohol [396] have also been used to study the residue analysis of 4-chloro-2-methylphenoxy acetic acid and 4-chloro-2-methylphenoxybutyric acid. Pentafluorobenzyl derivatives of phenols and carboxylic acids were prepared for detection by electron capture at very low levels [400,401 ]. 

Phenoxyacetic acid herbicide Extraction method Comments Reference... 

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