Volatile organic halocarbons

Finally, there are also pollutants that do not cause direct health impacts hut that may have the potential to cause harm indirectly, through their actions on the overall ecology, or as they function as precursor chemicals that lead to the production of other harmful chemicals. The major indirect-action pollutants include volatile organic carbon (VOC) compounds that act as precursors to more harmful species chemicals called halocarbons and chemicals called greenhouse gases. 

Gas-phase, solution-phase, and heterogeneous reactions all play important roles in atmospheric chemistry. The mean atmospheric composition is given in Table 1. N2, O2, and Ar comprise 99.9% of the atmosphere and, for all practical purposes, the relative proportion of these gases is constant in the lower 100 km of the atmosphere. We are concerned here with the fate of pollutants such as CO, volatile organic compounds, halocarbons, sulfur compounds, and nitrogen oxides, which are present in trace amounts and whose concentrations vary significantly both spatially and temporally. 

Equilibrating a gas two or more times with an aqueous sample (waters, sediment slurries, biological fluids) permits calculation of distribution coefficients and measurements of volatile organic compounds, such as hydrocarbons and halocarbons at sub-fxg/L concentrations. Classes of volatile organic compounds have different distribution coefficients, which aids in their separation and identification. The multiple gas-phase equilibration method has been used to measure the solubilities of pure hydrocarbons in waters of various salinities and of volatile hydrocarbons in oils and in water from the Cook Inlet, Gulf of Mexico, and Santa Barbara Channel It was first to detect small amounts of chloroform and other contaminants in New Orleans drinking water it measured the loss of C1-C10 hydrocarbons from oil slicks on the ocean surface and the apparent absence of dissolved hydrocarbons under the slicks in less than 8 hr. It has simultaneously measured up to 8 anesthetic gases in blood and plasma. 

Gas-solid chromatography is used for a narrower range of separations than gas-liquid chromatography. Because of higher retention, typical applications are the separation of fixed gases, volatile hydrocarbons, halocarbons, organic solvents, and sulfur gases. The presence of immobilized active centers enhances the separation of isomers and isotopes. 

F. Laturnus, Volatile halocarbons released from Arctic macroalgae. Mar. Chem., 55 (1996), 359-366. F. Laturnus, C. Wiencke, H. Kloser, Antarctic macroalgae - sources of volatile halogenated organic compounds. Mar. Environ. Res., 41 (1996), 169-181. 

Bis(trifluoromethyl)mercury forms colorless, volatile crystals of pungent odor that melt at 163°. The crystals contain linear F3C—Hg—CFj units with inter-molecular F—Hg contacts. They are soluble in organic solvents, such as alcohols, ethers, halocarbons, and hydrocarbons, and also in water with slow decomposition. The F NMR spectrum of a solution in CHjCN consists of a singlet at — 37.8 ppm (upheld from CFClj) with g satellites (V gp 13(X) Hz) major IR bands are at 1145 (vs), 1070 (vs), 713 (m), and 272 (s) cm . ... 

The sensor array responses were determined for a series of different volatiles representing the common organic functionalities amines, arenes, alcohols, aldehydes, carboxylic acids, esters, halocarbons, ketones, phosphines, sulfides, and thiols. Each analyte response is represented as the red, green, and blue values of each of the 24 dyes, that is, a 72-dimensional vector. These results suggest that the familial similarities among compounds of the same functionality are exceptional amines, alcohols, aldehydes, esters, and so forth are all easily distinguished from each other. 

The mixture of glycerin and PVC emulsion is completely absorbed by sponge cubes, which are further tumbled to achieve uniform distribution of liquid. ITie impregnated cubes are exposed to 100"C for 30 min and at 127"C for 40 min, which is sufficient to sinter particles of PVC. Glycerin is washed out by water in the next step and cubes are dried. Cubes have a PVC/cellulose ratio of 3.41/1 and they have a microporous structure. The cubes are used to remove toxic organic species from water such as polychlorinated biphenyls, dioxins, polyaromatie hydrocarbons, nitroaromatics, pesticides, herbieides, and volatile halocarbons. 

Seawater contains considerable amounts of dissolved halogenated organic substances. The following chapter deals with the low relative molecular mass fraction, i.e., substances with one to four carbon atoms. This group of compounds is often called halocarbons or volatile halogenated organic compounds (VHOC). 

Short-chain halocarbons, volatile halogenated organic compounds (VHOCs), are another part of the VOCs group. Many of these compoimds are used in the industry. A subset is formed by disinfection by-products such as THMs, haloacetonitriles, etc. VOSCs lead to unpleasant odor in water by action of microorganisms. 

---