1,3 -Dichlorobenzene

Like ONCB, 1,4-dichlorobenzene (1,4-DCB) first caught the attention of regulatory agencies early in the era of modem environmental directives. Unlike 

Product Stewardship Life Cycle Analysis and the Environment 

which has been primarily used as an intermediate, 1,4-DCB has been used in consumer products with consequent potential for human and environmental exposure. Such exposures ultimately led to restrictions on its use in the European Union. This case study compares how scientists and regulators viewed this substance in two eras, the mid-1970s and some 40 years later. 

One of the first reports issued by the newly formed US EPA, just before fhe passage of TSCA, described the use of 1,4-DCB circa 1975 [50, p. 324]  

Para-dichlorobenzene in its solid form, 99% purity, is used for moth control and space-deodorants and sublimes at 50 F to a heavier-than-air vapor. Action fumigant against moths and their larvae, vapors act as a space deodorant, and a fungistat. As a moth control agent, a usage of 1 Ib./lOO cubic feet of confined space is recommended.. .. The p-dichlorobenzene should be kept at a level such that the fumes in the confined area are concentrated enough to cause irritation to the eyes. 

The 2003 ACGIH ceiling-threshold limit value (C-TLV) for dichloroacetylene is 0.1 ppm (0.39mg/m ) with an A3-animal carcinogen designation. 

Humphrey JH, McClelland M Cranial nerve palsies with herpes following general anaesthesia. A report from the central Middlesex County Hospital. Br Med J 1 315-318, 1946 

Greim H, Wolff T, Hofler M, Lahaniatis E Formation of dichloroacetylene from trichloroethylene in the presence of alkaline material—Possible cause of intoxication after abundant use of chloroethylene-containing solvents. Arch Toxicol ISGEIMll, 1984 

Saunders RA A new hazard in closed environment atmospheres. Arch Environ Health 14 380-384, 1967 

US Department of Health and Human Services (NIOSH) Occupational safety and health guidelines for chemical hazards. Supplement IV-OHG (pub no 95-121), Occupational safety 

Fire point Flaah point Freeaing point Heat of combuation Heat of fuaion 

Refractive index Q22 C Solubility in water QZ5 C Specific gravity Q20/4 C 

Specific beat Specific reaiativity Weight per gallon ttZS C 

Solubility in water 20 C Solubility ot water in eolvent Z0 C Specific gravity 20/20 C Vapor preseure 20 C Weight per gallon 20 C 

Not more than 5% die tiUs below 180 C Not lest than 95% distills below 190 C 

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In the hquid-phase chlorination, 1,3-dichlorobenzene is found only in a small quantity, and 1,3,5-trichlorobenzene and 1,2,3,5-tetrachlorobenzene are undetectable. The ratios of 1,4- to 1,2-dichlorobenzene with various catalysts are shown in Table 3. Iodine plus antimony trichloride is effective in selectively chlorinating 1,2,4-trichlorobenzene to 1,2,4,5-tetrachlorobenzene (22), however, 1,2,4,5-tetrachlorobenzene is of limited commercial significance. 

Table 3. Ratio of 1,4- to 1,2-Dichlorobenzene with Various Catalysts...

Dichlorobenzene is sold as two grades technical chlorobenzene <0.05, trichlorobenzenes <1.0, 1,2-dichlorobenzene 80, and other isomers <19.0 and purified, produced by redistilling the technical product in a very efficient stiU chlorobenzene <0.05, 1,2,4 trichlorobenzene <0.2 and 1,2-dichlorobenzene 98.0. 

Ainino-3-chloroanthraquiQone [84-46-8] (68) is prepared from 2,3-dichloroanthraquiQone by partial chlorine replacement by a NH2 group. 2,3-Dichloroanthraquiaone [84-45-7] (67) is prepared by Friedel-Crafts reaction of phthaUc anhydride and 1,2-dichlorobenzene followed by ring closure of the resultant benzoylbenzoic acidia sulfuric acid (94). 

Chemical Designations - Synonyms 1,2-Dichlorobenzene Downtherm E Orthodichlorobenzene Chemical Formula 0-CJH4CI2. 

Repeat the analysis with 1,2-dichlorocyclohexatriene to 1,2-dichlorobenzene. Are there one or two energy minima If two, which is more stable, the structure with the short C1C2 bond or the long C1C2 bond Explain. 

Due to the commercial availability of EMME in good purity, there has not been a need to develop new methods to prepare 3-anilino-acrylates therefore, only a few alternatives have been reported. One approach described thermal carbene generation from 37, and rearrangement to form 38. Cyclization in refluxing 1,2-dichlorobenzene (1,2-DCB) provided the 2, 3, 4-trisubstituted quinolines. An electron-withdrawing group (EWG) on the carbene carbon was required for this reaction, and therefore led to the EWG substitution in the 2-position of the quinoline. 

Thermolysis of the azido derivative 143 (R = R =H) in refluxing 1,2-dichlorobenzene gave the pyrroloquinoline 144 and the dihydropyrrolo derivative 145 amongst other products (79H1021), whereas its thermal... 

Numbers can also be used these three compounds may be referred to as 1,2-dichlorobenzene, 1,3-dichlorobenzene, and 1,4-dichlorobenzene, respectively. When three or more substituents are present, numbers become mandatory. 

Recently, uniform Filins with high concentrations of Cwl were cast from 1,2-dichlorobenzene solutions containing up to 1 4 weight ratio MEH-PPV [110]. For devices made from these high concentration blends, charge collection efficiencies around //,.=26% (electron/incident photon) and power conversion efficiencies around tjc-2.5% (electrical power out/incident light power) have been realized. 

Diverse derivatives 5 (X = F or N02) of diphenyldiazene have similarly been converted into ll/7-dibenzo[c,/][l,2]diazepines 6 in refluxing 1,2-dichlorobenzene with the elimination of hydrogen fluoride or nitrous acid, respectively.150... 

A1C1, (0.8 g, 6 mmol) was added to a solution of the chloride 1 (1.6 g, 5.2 mmol) and a nitrile (6 mmol) in 1,2-dichlorobenzene and the mixture was heated at 120-130 C for 20 min. The mixture was cooled, made alkaline with dil aq NaOH and extracted with Et20. The solvents were removed by steam distillation and the residue was chromatographed (silica gel. EtOAc/petroleum ether 1 9) to give the yellow product (deep red if R = Ar). 

Heating the acetyltriazepine 2 in 1,2-dichlorobenzene in a sealed tube at 190-200CC for 65 hours gives yV-acetyl-5,6-dimethoxypyrazin-2-amine (4) presumably via the bicyclic valence tautomer 3.371... 

Cyclization of l-bromo-19-methyl-1.19-dideoxybiladicnes-ac 11 to porphyrins 12 occurs simply by heating the tetrapyrrole in 1,2-dichlorobenzene solution or in few cases in dimethyl sulfoxide. 

A highly efficient construction of the steroidal skeleton 166 is reported by Kametani and coworkers111 in the intramolecular Diels-Alder reaction of the a, jS-unsaturated sulfone moiety of 165 (equation 117). Thus, when the sulfone 165 is heated in 1,2-dichlorobenzene for 6h, the steroidal compound 166 can be obtained in 62% yield. The compound 166 produces estrone (167) by elimination of benzenesulfinic acid and subsequent hydrogenation of the formed double bond. The stereoselectivity of the addition reflects a transition state in which the p-tosyl group occupies the exo position to minimize the steric repulsion between methyl and t-butoxy groups and the o-quinodimethane group as shown in equation 117. 

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