Dichlorotoluenes

Mono- and dichlorotoluenes ate used chiefly as chemical iatermediates ia the manufacture of pesticides, dyestuffs, pharmaceuticals, and peroxides, and as solvents. Total annual production was limited prior to 1960 but has expanded greatly siace that time. Chlorinated toluenes ate produced ia the United States, Germany, Japan, and Italy. Siace the number of manufacturers is small and much of the production is utilised captively, statistics covering production quantities ate not available. Worldwide annual production of o- and -chlorotoluene is estimated at several tens of thousands of metric tons. Yearly productions of polychlorotoluene ate ia the range of 100—1000 tons. 

Reactions of the Aromatic Ring. Ring chlorination of o-chlorotoluene yields a mixture of all four possible dichlorotoluenes, the 2,3-, 2,4-, 2,5-, and 2,6-isomers as shown in equation 1 (14). 

The rate of chlorination of toluene relative to that of ben2ene is about 345 (61). Usually, chlorination is carried out at temperatures below 70°C with the reaction proceeding at a profitable rate even at 0°C. The reaction is exothermic with ca 139 kj (33 kcal) of heat produced per mole of monochlorotoluene formed. Chlorine efficiency is high, and toluene conversion to monochlorotoluene can be carried to about 90% with the formation of only a few percent of dichlorotoluenes. In most catalyst systems, decreasing temperatures favor formation of increasing amounts of -chlorotoluene. Concentrations of requited catalysts are low, generally on the order of several tenths of a percent or less. 

A study to isolate and examine the genetic characteristics of bacteria that metaboli2e chlorotoluenes, such as OCT, PCT, and 2,6-dichlorotoluene, has been reported (74). Two products were isolated from a study of the metaboHsm of PCT by Pseudomonasputida ... 

Dichlorotoluene (2,4-dichloro-l-methylben2ene) constitutes 80—85% of the dichlorotoluene fraction obtained in the chlorination of PCT with antimony trichloride (76) or zirconium tetrachloride (77) catalysts. It is separated from 3,4-dichlorotoluene (l,2-dichloro-4-methylben2ene), the principal contaminant, by distillation. Chlorination of OCT with sulfuryl chloride gives mainly 2,4-dichlorotoluene and small amounts of the 2,3 isomer (78). 

Dichlorotoluene (l,3-dichloro-2-methylben2ene) is formed in up to 60% yield in the sulftde-cocataly2ed chlorination of OCT. Purification by recrystahhation gives 99% pure product (15,16). 

Chlorination of OCT with chlorine at 90°C in the presence of L-type 2eohtes as catalyst reportedly gives a 56% yield of 2,5-dichlorotoluene (79). Pure 2,5-dichlorotoluene is also available from the Sandmeyer reaction on 2-amino-5-chlorotoluene. 3,4-Dichlorotoluene (l,2-dichloro-4-methylben2ene) is formed in up to 40% yield in the chlorination of PCT cataly2ed by metal sulfides or metal halide—sulfur compound cocatalyst systems (80). 

Dichlorotoluene (l,2-dichloro-3-methylben2ene) is present in about 10% concentration in reaction mixtures resulting from chlorination of OCT. It is best prepared by the Sandmeyer reaction on 3-arnino-2-chlorotoluene. 

Dichlorotoluene (l,3-dichloro-2-methylben2ene) is prepared from the Sandmeyer reaction on 2-arnino-6-chlorotoluene. Other methods include ring chlorination of -toluenesulfonyl chloride followed by desulfonylation (81), and chlorination and dealkylation of 4-/ f2 -butyltoluene (82) or... 

Dichlorotoluene is an intermediate for manufacture of herbicides. It is also used to obtain 2,4-dichloroben2yl chloride and 2,4-dichloroben2oyl chloride. 2,6-Dichlorotoluene is appHed as a herbicide and dyestuff intermediate. 2,3,6-Trichlorotoluene is used as a herbicide intermediate. The other polychlorotoluenes have limited industrial appHcation. 

Benzal chloride [(dichloromethyl)benzene, a,a-dichlorotoluene, benzylidene chloride], C H CHCl, is a colorless Hquid with a pungent, aromatic odor. Benzal chloride is insoluble in water at room temperature but is miscible with most organic solvents. 

Case 2 - The Hyde Park Landfill site, located in an industrial complex in the extreme northwest corner of Niagara, New York, was used from 1953 to 1975 as a disposal site for an estimated 80,000 tons of chemical waste, including chlorinated hydrocarbons. A compacted clay cover was installed in 1978 over the landfill and a tile leachate collection system was installed in 1979. Hazardous compounds such as ortho-, meta- and para-chlorobenzoic acid toluene ortho- and meta-chlorotoluene 3,4-dichlorotoluene and 2,6-dichlorotoluene were detected in the leachate (Irvine et al., 1984). Since 1979, the existing leachate treatment system has used activated carbon as the technology for removing organic carbon. Although... 

Methyl 2,3-diamino-6-methylbenzoate gave methyl 6-methyl-2,3-dioxo-l,2,3,4-tetrahydro-5-quinoxalinecarboxylate (252) [(C02H)2,4M HCl, reflux, 90 min 69% note survival of the ester grouping]. 2,3-Diamino-5,6-dichlorotoluene gave 6,7-dichloro-5-methyl-2,3(l//,4//)-quinoxalinedione (253) [(C02H)2, 4M HCl, reflux, 6 h 66%], 2-Isopropylaminoaniline gave l-isopropyl-2,3(l//,4//)-quinoxalinedione (254)... 

Hindered lithium dialkylamides can generate aryl-substituted carbenes from benzyl halides.162 Reaction of a,a-dichlorotoluene or a,a-dibromotoluene with potassium r-butoxide in the presence of 18-crown-6 generates the corresponding a-halophenylcarbene.163 The relative reactivity data for carbenes generated under these latter conditions suggest that they are free. The potassium cation would be expected to be strongly solvated by the crown ether and it is evidently not involved in the carbene-generating step. 

Miconazole nitrate was prepared by Godefori and co-workers [5-7]. Imidazole 1 was coupled with brominated 2,4-dichloroacetophenone 2 and the resulting ke-tonic product 3 was reduced with sodium borohydride to its corresponding alcohol 4. The latter compound 4 was then coupled with 2,4-dichlorotoluene by sodium borohydride in hexamethylphosphoramide (an aprotic solvent), which was then extracted with nitric acid to give miconazole nitrate. 

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