From Halocarbons

In the last decade, the refrigerant issue is extensively discussed due to the accepted hypothesis that the chlorine and bromine atoms from halocarbons released to the environment were using up ozone in the stratosphere, depleting it specially above the polar regions. Montreal Protocol and later agreements ban use of certain CFCs and halon compounds. It seems that all CFCs and most of the HCFCs will be out of produc tion by the time this text will be pubhshed. 

The preparation of metal dithiophosphate complexes usually involves the reaction of metal halides or acetates with dithiophosphoric acids or their salts. The metal complexes are generally purified by repeated fractional crystallization from halocarbon solvents such as chloroform. The reactions of mixtures of alcohols and alcohols and phenols with phosphorus(V) sulfide allegedly,... 

Obtainable from Halocarbon Products Corp., 82 Burlews Court, Hackensack, NJ, 07601. 

Figure 13.7 shows the effective total tropospheric concentration of chlorine from halocarbons from 1992 to 1996 (Montzka et al., 1996a). The concentration peaked in 1994 at 3.0 ppb, but when methyl chloride (CH-,C1) and other chlorinated organics are taken into account, the peak was likely 3.7 ppb. The total tropospheric chlorine concentration in mid-1995 decreased at a rate of approximately 25 ppt per year, in contrast to increases of 110 ppt per year in 1989 (Montzka et al., 1996a Cunnold et al., 1997). Bromine compounds show the same trend. As a result, the stratospheric levels of chlorine and bromine are expected to peak around the year 2000 (Montzka et al., 1996a World Meteorological Organization, 1995,1999). 

FIGURE 13.7 Effective total tropospheric concentration of chlorine from halocarbons from f992 to f996 in the Northern (------)... 

Montzka, S. A J. H. Butler, R. C. Myers, T. M. Thompson, T. H. Swanson, A. D. Clarke, L. T. Lock, and J. W. Elkins, Decline in the Tropospheric Abundance of Halogen from Halocarbons Implications for Stratospheric Ozone Depletion, Science, 272, 1318-1322 (1996a). 

Ramaswamy, V., M. D. Schwarzkopf, and K. P. Shine, Radiative Forcing of Climate from Halocarbon-Induced Global Stratospheric Ozone Loss, Nature, 355, 810-812 (1992). 

Solvents. Reagent grade THF (nD25 = 0.888, bp = 64-66°C) containing 0.025 wt-vol % di-ferf-butyl-p-cresol which served as an antioxidant was used for the preparative GPC fractionation. The solvent TFE (nD20 = 1.2907, d25 = 1.3823, bp = 76°C, ionization constant Ka — 4.3 X 10"13) was obtained from Halocarbon Products Corp., Hackensack, N. J., and was used for both analytical GPC and viscometry. The recovery and... 

I Li2[C(SiMe3)S02Ph] 4-7THF formation from halocarbons 10.2.2.6 C4oH6oFYb2... 

Li2[C(SiMe3)S02Ph] 6-Li20-1OTHF formation from halocarbons ... 

Li2Me3SiCCN) )2 6Et20-1 eye formation from halocarbons 10,2.6.6 C62H46N4Ti... 

Types of Halocarbon Photoreactions. In the following sections, we discuss several types of halocarbon photoreactions that provide sinks in aquatic environments. Emphasis in this chapter is placed on photoreactions that result in dehalogenation, in which halide ions (X ) are produced from halocarbons (RX). Here the term direct photoreactions indicates reactions that involve direct light absorption by the halocarbon itself (eq 4). 

Montzka S.A., Butler J.H., Meyers R.C., Thompson T.M., Swanson T.H., Clarke A.D., Lock L.T., ElkinsJ.W. (1996a) Decline in the tropospheric abundance of halogen from halocarbons implications for stratospheric ozone depletion. Science 212,1318-22. 

Available from Halocarbon Products Corp., 82 Burlews Court, Hackensack, N.J., Series 25-10M. Apiezon N stopcock grease is attacked by bromine but was successfully used by the checkers. However, it must be replaced before the vacuum line is used for other work. Available from Matheson Gas Products, East Rutherford, N.J. 07073. 

Li2 C(SiMe,)S02Ph]) LijO lOTHF Formation from halocarbons 14, 10.2.2.6 40 901 14 6RU2... 

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