Methoxychlor Methoxy-DDT

Methoxychlor, see Methoxychlor p,p -Methoxychlor, see Methoxychlor Methoxy-DDT, see Methoxychlor... 

Di (p-methoxyphenyl) trichloromethyl methane DMDT p,p -DMDT p,p -Methoxychlor Methoxy DDT... 

CsH40CH3)2CHCCl3 Combustible solid difficult to ignite. Liquid forms are dissolved in hydrocarbons (flash point about 100 to 150°F/38 to 66°C). Contact with strong oxidizers may cause fire and explosions. Incompatible with alkaline materials hydrolyzes in alkali. Attacks some plastics, mbber and coatings iron and aluminum. METHOXY DDT (72-43-5) see methoxychlor. 

Synonyms 2,2-Bis(p-anisyl)-1,1,1 -trichloroethane 1,1 -Bis(p-ethoxyphenyl)-2,2,2-trichloroethane 2,2-Bis(p-methoxyphenyl)-1,1,1-trichloroethane Chemform 2,2-Di-/ -anisyl-1,1,1 -trichloroethane Dimethoxy-DDT j9,/> -Dimethoxydiphenyltrichloroethane Dimethoxy-DT 2,2-Di(p-methoxyphenyl)-1,1,1 -trichloroethane Di(p-methoxyphe-nyl)trichloromethyl methane DMDT 4,4 -DMDT p,p -DMDT DMTD ENT 1716 Maralate Marlate Marlate 50 Methoxcide Methoxo 4,4 -Methoxychlor />,/> -Methox-ychlor Methoxy-DDT Metox Moxie NCI-C00497 RCRA waste number U247 1,1,1-Trichloro-2,2-bis(p-anisyl)ethane 1,1,1 -Trichloro-2,2-bis(p-methoxyphenol)ethanol 1,1,1 -Trichloro-2,2-bis(p-methoxypheny l)ethane 1,1,1 -Trichloro-2,2-di(4-methoxyphe-nyl)ethane 14 -(2,2,2-Trichloroethylidene)bis(4-methoxybenzene). 

The apparent rate of hydrolysis and the relative abundance of reaction products is often a function of pH because alternative reaction pathways are preferred at different pH. In the case of halogenated hydrocarbons, base-catalyzed hydrolysis will result in elimination reactions while neutral hydrolysis will take place via nucleophilic displacement reactions. An example of the pH dependence of hydrolysis is illustrated by the base-catalyzed hydrolysis of the structurally similar insecticides DDT and methoxy-chlor. Under a common range of natural pH (5 to 8) the hydrolysis rate of methoxychlor is invariant while the hydrolysis of DDT is about 15-fold faster at pH 8 compared to pH 5. Only at higher pH (>8) does the hydrolysis rate of methoxychlor increase. In addition the major product of DDT hydrolysis throughout this pH range is the same (DDE), while the methoxychlor hydrolysis product shifts from the alcohol at pH 5-8 (nucleophilic substitution) to the dehydrochlorinated DMDE at pH > 8 (elimination). This illustrates the necessity to conduct detailed mechanistic experiments as a function of pH for hydrolytic reactions. 

Methoxychlor is degraded in vivo by 0-dealkylation and excreted as mono-and bis-phenols. It is much less environmentally persistent also much less toxic to rats (oral LD q> 6000 mg/Kg compared with LD q 118 mg/Kg for DDT Metcalf, ref. 16). However, methoxychlor toxicity in fish approaches that of DDT, and in cold water fish, e.g., Atlantic salmon, it can accumulate to excessive levels. Although much less toxic in mammals than DDT it is similar in its estrogenic action. Methylchlor is less toxic to fish than methoxychlor, but also rather ineffectual as an insecticide. Comparison of the persistence characteristics of the methyl and methoxy analogs of DDT shows the microsomal side chain oxidation of the alkyl group to be more efficient than microsomal 0-dealkylation. 

Strategy. The only structural difference between these two molecules is the replacement of two chlorine atoms on DDT with two methoxy (also written as OCH3) moieties on methoxychlor. Thus, we can use the pi-values of these two groups to first remove the two chlorines and then add the two methoxys. 

Synonyms 1,1,1 -Trichloro-2,2-bis(p-methoxyphe-nyl)-ethane l,l -(2,2,2-Trichloroethylidene)bis(4-methoxy-benzene) Dimethoxy-DT DMDT ENT 1716 Higalmetox Methoxychlore Marlate Met-hoxy-DDT OMS 466 Prentox Marlate Met-ox Chemform... 

Muller himself and other entomologists tested a wide array of compounds similar to DDT in order to reveal the relationship between structure and activity. The most important outcome besides DDT was methoxychlor having p,p -methoxy groups instead of p,p -chloro groups. The methoxy groups have approximately the same size and shape as the chloro groups. 

Methoxychlor is much less stable and became popular when the environmental contamination caused by DDT was recognized. The methoxy groups are easily attacked by oxidative enzymes (CYP enzymes). Ethyl groups in the para position are also possible, as in Perthane. Another DDT analogue, more active as a miticide, is dicofol. The structures of DDT and some of the more important derivatives are shown. 

The groups on the phenyl rings appear to have some effect on the reductive dechlorination of the trichloroethane. Thus, o,p -DDT is de-chlorinated reductively to o,p -DDD by mechanisms and rates similar to the reductive dechlorination of p,p -DDT 17, 25). In contrast, Mendel et al. 17) were unable to obtain reductive dechlorination when the phenyl chlorine atoms of p,p -DDT were replaced by ethyl or methoxy groups. It is interesting, however, that they were unable to recover completely the methoxychlor. This indicates anaerobic degradation of this compound by some other route. 

Although the toxic properties are more or less the same for structurally similar compounds, such as Heptachlor and Chlordane, the degree of toxicity may vary significantly with chlorosubstitution in the compound. For example, substitution of chlorine atoms with methoxy group in the aromatic rings in DDT decreases the latter s toxicity. Thus, the methoxy derivative, Methoxychlor, is significantly less toxic than DDT. Similarly, ethyl-substituted Perthane is much less toxic than p,p -DDD. 

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