Hydrocarbons, halogenated

Substituting a diird chlorine on the methane molecule results in the compound whose proper name is trichloromediane (tri- for three chloro- for chlorine and methane, the hydrocarbon s name for die one-carbon chain). It is more commonly known as chloroform. Its molecular formula is CHC13. Chlorofonn is a heavy, colorless, volatile liquid with a sweet taste and characteristic odor. It is classified as non-flammable, but it will bum if exposed to high temperatures for long periods of time. It is narcotic by inhalation and toxic in high concentrations. It is an insecticide and a fumigant and is very useful in the manufacture of refrigerants. 

What was true for one hydrocarbon compound is true for most hydrocarbon compounds, particularly straight-chain hydrocarbons that is, you may substitute a functional group at each of the bonds where a hydrogen atom is now comiected to the carbon atom. Where four hydrogen atoms exist in methane, there are six hydrogen atoms in ethane you recall that the difference in 

Fire and Explosion Hazards Handbook of Industrial Chemicals 

Although we are using chlorine as the functional group, it may be any of the other halogens. In addition, we are giving the common names, while the proper names may be used on the labels and shipping papers. Ethyl chloride s proper name is chloroethane. 

There are many uses for the halogenated hydrocarbons. Many of them are flammable most are combustible. Some halogenated hydrocarbons are classified as neither, and a few are excellent fire-extinguishing agents (the Halons ), but they will all decompose into smaller, more harmful molecular fragments when exposed to high temperatures for long periods of time. 

The commercial grade is purified by washing with portions of concentrated sulphuric acid until the acid layer remains colourless, and then with water, sodium carbonate solution and water again. It is dried initially over calcium chloride and then distilled from calcium hydride before use. The fraction b.p. 40-41 °C is collected. Dichloromethane should be stored in a brown bottle away from light over Type 3A molecular sieve. 

Dichloromethane is a useful substitute for diethyl ether in extraction processes when it is desired to employ a solvent which is more dense than water. 

Alternative drying agents for chloroform are phosphorus pentoxide, calcium sulphate, or powdered Type 4A molecular sieve. 

Pure chloroform has b.p. 61 °C/760mmHg. It must not be dried by standing with sodium or an explosion may occur. The solvent, when free of alcohol, should be kept in the dark in order to avoid the photochemical formation of dangerous quantities of phosgene. 

CAUTION Carbon tetrachloride is a suspect carcinogen avoid breathing vapour and contact with the skin or eyes. 

Secondary reactions then follow involving these and subsequently formed radicals. The nature of the species formed in the primary photolytic act has been inferred from the product distribution and other kinetic evidence, and also from observations of transient spectra during flash photolysis studies. For example, spectra characteristic of CIO, BrO, and 10 have been observed following the flash photolysis of methyl chloride , methyl bromide and methyl iodide in the presence of oxygen, and the absorption spectrum of the free methyl radical has been ob-served during the flash photolysis of methyl iodide and methyl bromide. 

In the case of iodides particularly, unless some radical scavenging agent is present, reactant molecules may be reformed either by the reverse of the above dissociation reaction or by the step 

In view of the action of trace impurities, many early observations on product distributions and on quantum yields in photolysis studies should be regarded with caution, particularly in the case of solution or liquid phase in which the reaction behaviour is extremely sensitive to traces of oxygen .  

Early studies on the photolysis of methyl iodide have been summarised by Emschwiller . In the gas phase at 25 °C with A 2537 A the main hydrocarbon products methane, ethane and ethylene, in the approximate 

The relatively large quantity of methane formed in the gas phase photolysis of methyl iodide is hard to reconcile with step (3) for which the activation energy would be about 9 kcal.mole . Schultz and Taylor showed that methane formation is independent of temperature over the range 40-100 °C and is also reasonably independent of iodine concentration. They therefore proposed that methane formation proceeds via a hot radical mechanism as follows 

Radicals of the alkanes are referred to as alkyl radicals. There are two other important radicals - the vinyl radical, which is produced when a hydrogen atom is removed from ethylene, and the 

Substituting another chlorine produces ethylene dichloride, whose proper name is 1,2-dichloroethane. In this case, an isomer is possible, which would be the chlorinated hydrocarbon where both chlorines attached themselves to the same carbon atom, whereby 1,1-dichloroethane is formed. These compounds have slightly 

The broken bonds (boldface = dissociated atom), AfH°(R), kcal/mol (kj/mol) 

1-Difluoro-l-chloro-e thane CF2CICH2-H 104.9 1.8 439.0 7.5 Review 2005GIA 

The aqueous photochemistry of simple chlorinated benzenes has been studied by only a few authors. The sunlight extinction of chlorobenzenes is quite low (8297 for PhCl = 0.12 [Dulin et al., 1986]), and their solubilities (especially for the more highly chlorinated isomers) are also relatively low. Chlorobenzene triplets appear to react by homolysis to phenyl radicals and chlorine atoms the subsequent fate of these radicals depends on the solvent used. Dulin et al. (1986) and Boule et al. (1987) indicated that monochlorobenzene was photohydrolyzed to phenol with a quantum yield of about 0.1 to 0.5. Additional very polar products were also observed, but no benzene. These quantum yields are similar to those observed in organic solvents however, the principal fate of photolyzed chlorobenzenes in organic solvents is reduction by hydrogen donation. Dichloro- and trichlorobenzenes were similarly converted to monochloro- and dichlorophenols, respectively, in water. The quantum efficiency for trichlorobenzene photodestruction in 10% acetonitrile was about 0.03 (Choudhry and Hutzinger, 1984). 

Hexachlorobenzene was very slowly photolyzed by direct or acetone-sensitized mechanisms (Choudry and Hutzinger, 1984), but it was photodecomposed much more rapidly (10-6(K)x) in the presence of various amine and indole derivatives (Hirsch and Hutzinger, 1989). Pentachlorobenzene was the only product identified in the amine experiments. Although no mechanistic speculations were engaged in by the authors, it appears plausible that electron transfer within ir-bonded complexes in the excited state could account for the observed rate enhancements. 

Hexachlorocyclopentadiene (23) is a widely used synthetic intermediate, produced in large quantities for the manufacture of pesticides and flame retardants. In the 

Although the maximum UV absorbance of PCBs occurs at wavelengths much shorter than those of sunlight, there is still sufficient extinction above 290 nm to permit some reactions to occur. In the presence of oxygen, these reactions are 

Only a few organoiodine compounds are of environmental importance. Methyl iodide, a metabolic product of some marine and freshwater algae, produces CHj and I by direct photolysis (Zafiriou, 1983). 

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Combustion in an incinerator is the only practical way to deal with many waste streams.This is particularly true of solid and concentrated wastes and toxic wastes such as those containing halogenated hydrocarbons, pesticides, herbicides, etc. Many of the toxic substances encountered resist biological degradation and persist in the natural environment for a long period of time. Unless they are in dilute aqueous solution, the most effective treatment is usually incineration. 

The main synthetic fluids used as special lubricants are esters, polyglycols, silicones, halogenated hydrocarbons and polyphenyl ethers. 

From the mono-halogenated hydrocarbon. The halogenated hydrocarbon is converted into the Grignard reagent and the latter allowed to react with diethyl carbonate, for example ... 

Typical nonsieve, polar adsorbents are siUca gel and activated alumina. Kquilihrium data have been pubUshed on many systems (11—16,46,47). The order of affinity for various chemical species is saturated hydrocarbons < aromatic hydrocarbons = halogenated hydrocarbons < ethers = esters = ketones < amines = alcohols < carboxylic acids. In general, the selectivities are parallel to those obtained by the use of selective polar solvents in hydrocarbon systems, even the magnitudes are similar. Consequendy, the commercial use of these adsorbents must compete with solvent-extraction techniques. 

Reference methods for criteria (19) and hazardous (20) poUutants estabHshed by the US EPA include sulfur dioxide [7446-09-5] by the West-Gaeke method carbon monoxide [630-08-0] by nondispersive infrared analysis ozone [10028-15-6] and nitrogen dioxide [10102-44-0] by chemiluminescence (qv) and hydrocarbons by gas chromatography coupled with flame-ionization detection. Gas chromatography coupled with a suitable detector can also be used to measure ambient concentrations of vinyl chloride monomer [75-01-4], halogenated hydrocarbons and aromatics, and polyacrylonitrile [25014-41-9] (21-22) (see Chromatography Trace and residue analysis). 

The question as to whether a flame retardant operates mainly by a condensed-phase mechanism or mainly by a vapor-phase mechanism is especially comphcated in the case of the haloalkyl phosphoms esters. A number of these compounds can volatilize undecomposed or undergo some thermal degradation to release volatile halogenated hydrocarbons (37). The intact compounds or these halogenated hydrocarbons are plausible flame inhibitors. At the same time, thek phosphoms content may remain at least in part as relatively nonvolatile phosphoms acids which are plausible condensed-phase flame retardants (38). There is no evidence for the occasionally postulated formation of phosphoms haUdes. Some evidence has been presented that the endothermic vaporization and heat capacity of the intact chloroalkyl phosphates may be a main part of thek action (39,40). 

Aqueous mineral acids react with BF to yield the hydrates of BF or the hydroxyfluoroboric acids, fluoroboric acid, or boric acid. Solution in aqueous alkali gives the soluble salts of the hydroxyfluoroboric acids, fluoroboric acids, or boric acid. Boron trifluoride, slightly soluble in many organic solvents including saturated hydrocarbons (qv), halogenated hydrocarbons, and aromatic compounds, easily polymerizes unsaturated compounds such as butylenes (qv), styrene (qv), or vinyl esters, as well as easily cleaved cycHc molecules such as tetrahydrofuran (see Furan derivatives). Other molecules containing electron-donating atoms such as O, S, N, P, etc, eg, alcohols, acids, amines, phosphines, and ethers, may dissolve BF to produce soluble adducts. 

Halogenated hydrocarbons that are inexpensive sometimes are used alone or in blends with phosphate esters as fire-resistant hydrauHc fluids. Other halogenated fluids are used for oxygen-compressor lubricants, lubricants for vacuum pumps that are in contact with corrosive materials, solvent-resistant lubricants, and other lubricant appHcations where highly corrosive or reactive materials are being handled. 

Commercial cmde lecithin is a brown to light yeUow fatty substance with a Hquid to plastic consistency. Its density is 0.97 g/mL (Uquid) and 0.5 g/mL (granule). The color is dependent on its origin, process conditions, and whether it is unbleached, bleached, or filtered. Its consistency is deterrnined chiefly by its oil, free fatty acid, and moisture content. Properly refined lecithin has practically no odor and has a bland taste. It is soluble in aflphatic and aromatic hydrocarbons, including the halogenated hydrocarbons however, it is only partially soluble in aflphatic alcohols (Table 5). Pure phosphatidylcholine is soluble in ethanol. 

Stabilized lithium acetyhde is not pyrophoric or shock-sensitive as are the transition-metal acetyhdes. Among its uses are ethynylation of halogenated hydrocarbons to give long-chain acetylenes (132) and ethynylation of ketosteroids and other ketones in the pharmaceutical field to yield the respective ethynyl alcohols (133) (see Acetylene-derived chemicals). 

At room temperature, HDPE is not soluble in any known solvent, but at a temperature above 80—100°C, most HDPE resins dissolve in some aromatic, aflphatic, and halogenated hydrocarbons. The solvents most frequently used for HDPE dissolution are xylenes, tetralin, decalin 1,2,4-trimethylbenzene, o-dichlorobenzene, and 1,2,4-ttichlorobenzene. 

Chemical Properties and Reactivity. LLDPE is a saturated branched hydrocarbon. The most reactive parts of LLDPE molecules are the tertiary CH bonds in branches and the double bonds at chain ends. Although LLDPE is nonreactive with both inorganic and organic acids, it can form sulfo-compounds in concentrated solutions of H2SO4 (>70%) at elevated temperatures and can also be nitrated with concentrated HNO. LLDPE is also stable in alkaline and salt solutions. At room temperature, LLDPE resins are not soluble in any known solvent (except for those fractions with the highest branching contents) at temperatures above 80—100°C, however, the resins can be dissolved in various aromatic, aUphatic, and halogenated hydrocarbons such as xylenes, tetralin, decalin, and chlorobenzenes. 

At temperatures near the critical temperature, many organic degradation reactions are rapid. Halogenated hydrocarbons loose the halogen in minutes at 375°C (38). At temperatures typical of nuclear steam generators (271°C (520°F)), the decomposition of amines to alcohols and acids is well known (39). The pressure limits for the treatment of boiler waters using organic polymers reflect the rate of decomposition. 

PMVEMA, supphed as a white, fluffy powder, is soluble in ketones, esters, pyridine, lactams, and aldehydes, and insoluble in aUphatic, aromatic, or halogenated hydrocarbons, as well as in ethyl ether and nitroparaffins. When the copolymer dissolves in water or alcohols, the anhydride group is cleaved, forming the polymers in free acid form or the half-esters of the corresponding alcohol, respectively. Table 7 illustrates the commercially available alternating copolymers and derivatives. 

Both lindane [58-89-9] (14) and hexachlorocyclopentadiene [77-47-4] (15) are halogenated hydrocarbons unlike the PCBs and PCNs, they do not contain an aromatic ring. 

It is important to produce HCl rather than elemental chlorine, CI2, because HCl can be easily scmbbed out of the exhaust stream, whereas CI2 is very difficult to scmb from the reactor off-gas. If the halogenated hydrocarbon is deficient in hydrogen relative to that needed to produce HCl, low levels of water vapor may be needed in the entering stream (45) and an optional water injector may be utilized. For example, trichloroethylene [79-01 -6] C2HCI2, and carbon tetrachloride require some water vapor as a source of hydrogen (45). 

Groundwater contaminated with chlorinated hydrocarbons is being remediated by a conventional air stripper or a rotary stripper, producing an air stream containing the halogenated hydrocarbon vapors and saturated with water vapor (45), which is then passed through a catalyst bed. 

In the late 1980s, however, the discovery of a noble metal catalyst that could tolerate and destroy halogenated hydrocarbons such as methyl bromide in a fixed-bed system was reported (52,53). The products of the reaction were water, carbon dioxide, hydrogen bromide, and bromine. Generally, a scmbber would be needed to prevent downstream equipment corrosion. However, if the focus of the control is the VOCs and the CO rather than the methyl bromide, a modified catalyst formulation can be used that is able to tolerate the methyl bromide, but not destroy it. In this case the methyl bromide passes through the bed unaffected, and designing the system to avoid downstream effects is not necessary. Destmction efficiencies of hydrocarbons and CO of better than 95% have been reported, and methyl bromide destmctions between 0 and 85% (52). 

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