Phenoxyalkanoic Acids

In marked contrast to hydrophobic compounds, more polar ones tend to be less adsorbed and to reach relatively high concentrations in soil water. Phenoxyalkanoic acids such as 2,4-D and MCPA are good examples (Figure 4.3). Their half-lives in soil are measured in weeks rather than years, and they are more mobile than OC insecticides in soils. When first applied they are lost only slowly. After a lag period of a... 

To prevent this contamination, there were several approaches which this mechanistic information suggested. But the one which the manufacturers proposed ( ) was to stop using nitrite to control corrosion of the container. Most dimethylamine phenoxyalkanoic acid products now contain non-detectable NDMA (18). 

Natural systems may be quite complex. For example, the enantiomerization of phenoxyalkanoic acids containing a chiral side chain has been studied in soil using H20 (Buser and Muller 1997). It was shown that there was an equilibrium between the R- and 5-enantiomers of both 2-(4-chloro-2-methylphenoxy)propionic acid (MCPP) and 2-(2,4-dichlorophenopxy)propionic acid (DCPP) with an equilibrium constant favoring the herbicidally active / -enantiomers. The exchange reactions... 

Muller TA, SM Byrde, C Werlen, JR van der Meer, H-P Kohler (2004) Genetic analysis of phenoxyalkanoic acid degradation in Sphingomonas herbicidovorans MH. Appl Environ Microbiol 70 6066-6075. 

Buser H-R, MD Muller (1997) Conversion reactions of various phenoxyalkanoic acid herbicides in soil. 2. Elucidation of the enantiomerization process of chiral phenoxy acids from incubation in a DjO/soil system. Environ Sci Technol 31 1960-1967. 

Gintautas PA, SR Daniel, DL Macalady (1992) Phenoxyalkanoic acid herbicides in municipal landfill leachates. Environ Sci Technol 26 517-521. 

Table 7. Repeating unit composition of PHAs biosynthesized by P. oleovorans grown with various phenoxyalkanoic acids... 

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

Phenoxyalkanoic acid herbicides are not amenable to direct gas chromatographic determination because of the high polarity or low volatility of the compounds and must be converted to their... 

There are several routes for nitrosamine contamination in pesticides use of contaminated chemicals during synthesis, side reactions, use of nitrite as a preservative and corrosion inhibitor of metal containers and by reactions with environmental nitrosating agents. Over 300 formulations were shown to be contaminated with nitrosamines however, the main contamination was confined to 2,6-dinitroaniline herbicides, dimethylamino salts of phenoxyalkanoic acid herbicide, diethanolamine and triethanolamine salts of acid... 

The herbicide 2,4-D is itself a potent phytotoxin. However, a number of structurally related but inactive compounds may be converted by plants to 2,4-D following the activation process and thus act as herbicides. These phenoxyalkanoic acids are co-(2,4-dichlorophenoxy) alkanoic acids. The transformation may be viewed as shown in Fig. 12 as 6-(2,4-dichlorophenoxy)hexanoic acid as the parent compound. The sequence is called /1-oxidation because the steps in which two carbons are removed initially involve the oxidation of the /1-carbon to the aliphatic acid moiety. 

Loos MA (1975) Phenoxyalkanoic acids. In Kemey PC, Kaufman DD (eds) Herbicides chemistry, degradation and mode of action, vol 1. Marcel Dekker New York, pp 1-128 Lovley DR (1993) Dissimilatory metal reduction. Annual Review of Microbiology 47 263-290 Macalady DL, Wolfe NL (1983) New perspectives on the hydrolytic degradation of the organo-phosphorothionate insecticide chloropyrifos. J Agric Food Chem 31 1139-1147 Macalady DL, Wolfe NL (1985) Effects of sediment sorption and abiotic hydrolysis. J Agric Food Chem 33 167-173... 

Synthetic auxins Phenoxyalkanoic acids Benzoic acids Pyridinecarboxylic acids Quinolinecarboxylic acids 4... 

A new class of herbicides, the pyridylosy-phenoxyalkanoic acids, is typified by n-butyl 2-[4-(5-tnfluoromethyl-2-pyndyloxy)phenoxy] propionate, tradenamed Fusillade, active against annual and perennial grasses ... 

Phenoxyalkanoic acid herbicides are not amenable to direct gas chromatographic determination because of the high polarity or low volatility of the compounds and must be converted to their more volatile derivatives. The sensitivity of the electron capture detector towards alkyl esters of 4-chloro-2-methylphenoxy acetic acid, 4-chloro-2-methylphenoxy butyric acid, etc., is very poor. The methyl ester of 4-chloro-2-methylphenoxy acetic acid was 100 times less sensitive to electron affinity detection than the 2,4-D-methyl ester [396]. 

PCP (Pentachlorophenol) (See Chapter 14. Phenolic Compounds and Chapter 18. Insecticides) Phenoxyalkanoic acids ... 

Loos, M.A. (1975) Phenoxyalkanoic acids. In Herbicides, Chemistry, Degradation and Mode of Action. Vol. I, 2nd Edition, Kearney, P.C., Kaufmann, D.D., Editors, Marcel Dekker, New York. 

Uses In pure form, dicamba is a white crystalline solid. The technical acid is a pale buff crystalline solid. Dicamba is a benzoic acid herbicide that is used for the control of infestation on leaves and soil. Dicamba controls annual and perennial broadleaf weeds in grain crops and grasslands, and is used to control brush and bracken in pastures. It kills broadleaf weeds before and after they sprout. Legume weeds are killed by dicamba. In combination with a phenoxyalkanoic acid or other herbicides, dicamba is used in pastures, rangeland, and noncrop areas such as fencerows and roadways to control weeds.2,17... 

Lindane is relatively non-persistent, especially under anaerobic conditions, and although its more highly chlorinated residues may present the same problems as those of polychlorophenols, the less chlorinated residues should follow pathways similar to those established for the microbial degradation of the chlorinated phenoxyalkanoic acid herbicides. Recent evidence (46) indicates that certain microbes can dechlorinate DDT anaerobically, thereby making available intermediates which may undergo further aerobic attack, leading in principle to total degradation. The ultimate fate of the hexachloronorbornene nucleus of cyclodienes is still uncertain and this question continues to attract attention. 

Non-specific methods that employ simple methods and reagents have been frequently employed for determination of active ingredients. Total chlorine and acid content may, for example, be used to measure phenoxyalkanoic acids. These methods have been largely displaced by more specific methods, such as gas chromatography, but where specific methods are unavailable, as in the case of maneb, zineb, and other complex organometallic ethylene dithiocarbamate derivatives, indirect methods are used. 

Miiller, M.D. Buser, H.-R., Conversion reactions of various phenoxyalkanoic acid herbicides in soil. 1. Enantiomerization and enantioselective degradation of the chiral 2-phenoxypropionic acid herbicides Environ. Sci. Technol 1997, 31, 1953-1959. 

PHENOXYALKANOIC ACID DERIVATIVES C -f VoCHjCOOH CH, (4-Chlom-2-mthylphenoxy)aceSc add MPCA... 

ROLE OF HUMIC SUBSTANCES IN THE ENVIRONMENTAL CHEMISTRY OF CHLORINATED PHENOXYALKANOIC ACIDS AND ESTERS... 

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