Dichlorobenzene crystallization

Hepatic Effects. Liver effects reported in case studies in humans exposed to 1,4-dichlorobenzene via inhalation have included jaundice, cirrhosis, and atrophy (Cotter 1953). Estimates of exposure duration ranged from 1 to 18 months however, quantitative data on 1,4-dichlorobenzene levels were not available. One report was located that described a 3-year-old boy who may have ingested 1,4-dichlorobenzene crystals. Jaundice was reported, indicating that liver function was in some way compromised, although no further details were reported. No dermal exposures to 1,4-dichlorobenzene in humans were reported. The lack of reliable information regarding human exposures to 1,4-dichlorobenzene by all three routes of exposure makes it difficult to draw any helpful conclusions about the toxicity of 1,4-dichlorobenzene in humans. 

Dibromobenzene is planar in the gas phase (Bastiansen and Hassel, 1947). 1,4-Dichlorobenzene crystallizes in triclinic and monoclinic... 

Solubility and Solvent Resistance. The majority of polycarbonates are prepared in methylene chloride solution. Chloroform, i7j -l,2-dichloroethylene, yy -tetrachloroethane, and methylene chloride are the preferred solvents for polycarbonates. The polymer is soluble in chlorobenzene or o-dichlorobenzene when warm, but crystallization may occur at lower temperatures. Methylene chloride is most commonly used because of the high solubiUty of the polymer (350 g/L at 25°C), and because this solvent has low flammabiUty and toxicity. Nonhalogenated solvents include tetrahydrofuran, dioxane, pyridine, and cresols. Hydrocarbons (qv) and aUphatic alcohols, esters (see Esters, organic), or ketones (qv) do not dissolve polycarbonates. Acetone (qv) promotes rapid crystallization of the normally amorphous polymer, and causes catastrophic failure of stressed polycarbonate parts. 

The chlorination of benzene can theoretically produce 12 different chlorobenzenes. With the exception of 1,3-dichlorobenzene, 1,3,5-trichlorobenzene, and 1,2,3,5-tetrachlorobenzene, all of the compounds are produced readily by chlorinating benzene in the presence of a Friedel-Crafts catalyst (see Friedel-CRAFTS reactions). The usual catalyst is ferric chloride either as such or generated in situ by exposing a large surface of iron to the Hquid being chlorinated. With the exception of hexachlorobenzene, each compound can be further chlorinated therefore, the finished product is always a mixture of chlorobenzenes. Refined products are obtained by distillation and crystallization. 

The dichlorobenzene isomers have very similar vapor pressures making separation by distillation difficult. Crystallization is generally used in combination with distillation to obtain the pure 1,2 and 1,4-dichlorobenzene isomers. The small quantity of 1,3-dichlorobenzene isomer produced is not generally isolated as a pure product. Environmental concerns have led to the use of improved crystalliza tion systems that contain the products with minimal losses to the environment. 

The product separates as a gum from which the supernatant liquid is decanted, and the gum is triturated with 250 cc of water in order to induce crystallization. The crude product thus obtained is recrystallized from 3,200 cc of boiling water and then from 40% aqueous isopropyl alcohol yielding 4,5-dichlorobenzene-1,3-disulfonamide as a white solid, MP 228.5° to 229.0°C. 

Figure 20-8 shows the features of a horizontal center-fed column [Brodie, Aust. Mech. Chem. Eng. Trans., 37 (May 1979)] which has been commercialized for continuous purification of naphthalene and p-dichlorobenzene. Liquid feed enters the column between the hot purifying section and the cold freezing or recovery zone. Crystals are formed internally by indirect coohng of the melt through the walls of the refining and recoveiy zones. Residue liquid that has been depleted of product exits from the coldest section of the column. A spiral conveyor controls the transport of solids through the unit. 

Synonyms AI3-00050 BRN 1680023 Caswell No. 632 CCRIS 307 4-Chlorophenyl chloride p-Chlorophenyl chloride 1,4-DCB p-DCB Dichloricide 4-Dichlorobenzene p-Dichloro-benzene para-Dichlorobenzene 4-Dichlorobenzol p-Dichlorobenzol EINECS 203-400-5 EPA pesticide chemical code 061501 Evola NC1-C54955 NSC 36935 Paracide Para crystals Paradi Paradichlorobenzene Paradichlorobenzol Paradow Paramoth Paranuggetts Parazene Parodi PDB PDCB Persia-Perazol RCRA waste number U072 Santochlor UN 1592. 

The chemical 1,4-di chlorobenzene is usually called para-DCB or p-DCB, but there are about 20 additional names for it, including para crystals and paracide. It is also called paramoth because it is one of two chemicals commonly used to make mothballs. 1,4-Dichlorobenzene is used to make deodorant blocks used in garbage cans and restrooms, as well as to help control odors in animal-hoi ding facilities. 1,4-Dichlorobenzene has also been used as an insecticide on... 

Hepatic Effects. A single case study was located regarding hepatic effects in humans after oral exposure to 1,4-dichlorobenzene. In this case report, the author describes a 3-year-old boy who had been playing with crystals containing 1,4-dichlorobenzene for 4-5 days before being admitted to the hospital. On admission, the boy was jaundiced and his mucous membranes were pale. After a blood transfusion. 

Dichlorobenzene is produced by the chlorination of benzene or chlorobenzene in the presence of a catalyst (typically ferric oxide) followed by either fiactional distillation or crystallization of the resulting mixture of chlorinated benzenes to yield 1,4-dichlorobenzene (HSDB 1998 IRPTC 1985). 

Children are exposed to 1,4-diehlorobenzene primarily by inhalation of vapors from toilet deodorants, moth proofing crystals and moth balls used in the home or by consumption of moth balls. Consumption of 1,4-dichlorobenzene in foods (See Section 5.4.4) and drinking water (See Section 5.4.2) contaminated with 1,4-dichlorobenzene is thought to be a minor exposure pathway. There have been no body burden measurements made on children. 

In addition, individuals using space deodorants (air fresheners), toilet block deodorants, or moth repellents (moth balls or crystal) containing 1,4-dichlorobenzene in their homes have the potential for high exposure to this compound (Scuderi 1986). Indoor air concentrations resulting from the use of these products in bathrooms and closets have been measured at levels up to 1.3 mg/m (0.22 ppm) (Scuderi 1986). 

The formation of crystalline fulleride salts at the electrode occurs when less polar solvents and bulky cations are used for the electrosynthesis. The first fulleride salt was synthesized by Wudl by bulk electrolysis of in o-dichlorobenzene with tetraphenylphosphonium chloride as supporting electrolyte [39, 80]. This black microcrystalline material with the composition (Ph4P )3(Cgg )(Cr)2 exhibits an ESR line with a g-value of 1.9991 and a line width of 45 G at room temperature. Single crystals of the slightly different salts (Ph4P )2(Cgg )(Cr) and (Ph4P )2(C50 )(Br ) could be obtained by electrocrystallization and their crystal structure was determined [82, 83]. Magnetic measurements showed the presence of unpaired spins. 

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