The Chlorine Controversy

As NOTED IN the preceding chapter, almost all elemental chlorine is made as a by-product of caustic soda production, although the obsolete Deacon process of 1868 has been revived (with improvements) for recycling CI2 onsite in plants where chlorination of hydrocarbons forms gaseous HCl, an objectionable waste product  

The reaction is exothermic (see Exercise 12.1), but, since it is very slow, a catalyst is necessary. Nitric oxide, once again, can serve as an oxygen carrier, as in the lead chamber process (Section 10.2) and in reaction 10.8, where ( 113)28 generated in the kraft process is converted to DMSO. Even so, at the elevated temperatures required, reaction 12.1 needs to be forced to completion by absorption of the steam in concentrated sulfuric acid or some other desiccant. In variants of the Deacon process, copper chloride acts as the catalyst or as an intermediate for chlorine regeneration. 

Two-thirds of the chlorine produced in North America is consumed by the organic chemicals industry (25% goes to ethylene dichloride production alone). Pulp and paper mills account for another 15%, while 5% of the total is used in water treatment. All of these applications, however, have environmental implications that led to demands from activist groups that the production of chlorine derivatives be reduced (even, in the extreme view, phased out entirely). While these concerns are being taken seriously in all quarters, and some chlorinated products have already been banned, the fact is that chlorine-based technologies make, and will continue to malce, important positive contributions to human health and prosperity. Indeed, at the time of writing in 1996, chlorine consumption continues to rise, al- 

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R. Stone, Science, 1994, 265, 308 estrogen mimics and the chlorine controversy. 

The hydrogen-chlorine chain reaction has proved to be one of the most controversial systems yet studied. After thirty years of investigation Bodenstein43 was able to say in 1931 that every worker on the photochemical synthesis of HC1 had produced his own mechanism even as late as 1940 little positive information had been obtained. However, the accumulated techniques and experience had firmly established the importance of atom chain reactions. The mechanism of photo-initiation and propagation is the same as for the hydrogen bromide photosynthesis, a non-branching chain reaction... 

Some people object to the chlorination of water, and prefer to drink bottled spring water. There is controversy over the level of risk associated with chlorination, and over the possible benefits of spring water. For example, hypochlorous acid reacts with traces of organic materials in the water supply. These reactions can produce toxic substances, such as chloroform. Supporters of chlorination believe that these substances are present at very low, safe levels, but opponents of chlorination disagree. Complete the following practice problems to help you decide on your own opinion of chlorination. 

Although there has been some controversy over whether there is indeed a true ozone deficit problem (e.g., Crutzen et al., 1995), a combination of measured concentrations of OH, HOz, and CIO with photochemical modeling seems to indicate that it may, indeed, exist (Osterman et al., 1997 Crtuzen, 1997), although the source of the discrepancy remains unclear. Measurements of CIO in the upper stratosphere have found concentrations that are much smaller (by a factor of 2) than predicted by the models (e.g., Dessler et al., 1996 Michelsen et al., 1996). Because of the chlorine chemistry discussed later, model overestimates of CIO will also result in larger predicted losses of 03 and hence smaller concentrations. 

The eourBe of addition of phenols to epicMorohydrin has been a subject of some controversy, since one might suppose the Btrongly nucleophilic character of phenoxide ion to cause indiscriminate attack on the chlorine-substituted carbon atom and tbe epoxide ring... 

Another compound used in some countries as a hypnotic is lorazepam, which can show some rebound phenomena [18], A similar compound, the chlorinated derivative of temazepam, lormetazepam, shows marked rebound phenomena [19], Flunitrazepam is aparticularly controversial benzodiazepine [20], It has achieved notoriety as the date-rape drug, although documented instances of clandestine use are sparse. It has a high abuse potential, resulting in tight scheduling. However, it does not appear to have a particular propensity to prominent rebound or withdrawal problems. 

With the application of electron-capture (EC) and micro-coulometric detection to gas chromatograph effluents from i960, the era of the measurement of nothing in everything had arrived and the environmental controversy was truly on. It was easier to make an effective EC detector than to interpret the analytical results correctly and many of the identifications of chlorinated insecticide (OC) residues made in the early 1960s are undoubtedly suspect, especially since it was found in 1966 that widespread polychlorobiphenyl (FCB) contamination in the bio-sphere can simulate OC in gas chromatographic analysis. 

A. Tukker, Frames in the Toxicity Controversy Risk Assessment and Policy Analysis Related to the Dutch Chlorine Debate and the Swedish PVC Debate, Kluwer Academic Publishers, Dordrecht, The Netherlands, 1999, p.21. 

This was the opening of the so called chlorine controversy between Dr. John Davy and Dr. Murray, fervent supporter of the official theory. This debate took the form... 

In October, 1812, Sir Humphry wrote to his brother The controversy is closed [467c]. Nevertheless, Murray never accepted the chlorine theory [467b (Vol.l, p.l60),1465,1589e]. 

Levels of biomagnification of highly chlorinated PCBs, of DDT, DDE, and chlordane-related compounds were disturbingly high, and all of these compounds together with a-hexachloro[aaaaee] cyclohexane have been identified in the diet of Inuit who consume and are essentially dependent on the harvest of ring seal, beluga, eider, and arctic char (Cameron and Weis 1993). The more controversial issue of the risks as opposed to the benefits of such consumption has been addressed (Kinloch et al. 1992). 

The controversy has not hurt business for the chlorine industry, which is booming.238 There have been some shifts in the product line. Methylene chloride demand is dropping. More trichloroethylene is being produced as a feedstock for fluorocarbon production. More sodium chlorite is being produced as a precursor for chlorine dioxide to be used in the bleaching paper. The trend should start downward in the future as chlorine-free alternatives are found and as ageing plants are retired. 

We are dealing with a highly ordered array of substances. What that array is on the molecular level—i.e., how the plane of the chlorin ring is located with respect to these layers or with respect to the spherical globules of which the layers seem to be composed—is still a matter of controversy and remains one of the areas which this writer would like to see the physical chemists explore. It is necessary to bridge the gap between ordinary statistical molecular behavior and individual structures that can be seen. We do not know, for example, what the arrangement of the chlorophyll molecules is in the lamellar layers. Order is, however, the major factor with which we are left. 

Chloro-l,2-(and -2,l-)benzisothiazoles are useful synthetic intermediates, since the chlorine atom is readily displaced by nucleophiles (see Vol. 5, pp. 352, 355), and recently reported work has extended the range of products thereby obtained. l-Chloro-l,2-benzisothiazol-3-one (111), obtained by the chlorination of 1,2-benzisothiazoIin-3-one (110 n = 0), may also prove a useful intermediate. Saccharin (110 n = 2) and its derivatives continue to be the subject of numerous papers little has changed in regard to the carcinogenicity controversy (see Vol. 5, p. 353), but a typical example of a chemical paper is one in which it is shown how saccharin may be transformed into the imidazo-fused derivative (112) or the thiadiazocine (113). ... 

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