Remote chlorination

Photochemical remote chlorination of steroids through (dichloroiodo)arenes... 

Remote chlorination (6, 298-300). Breslow has extended his remote functionalization of steroids to a double functionalization at C, and Cn of cholestanol. Thus the ester (2) of cholestanol, prepared from a p-iodophenylnicotinic acid, when treated with 1 (1.2 equiv.) is chlorinated selectively at C9 chlorination of the same ester with 3 equiv. of C6H5IC12 results in chlorination at C9 and at C17 in quantitative yield. The para-iodo group of the ester plays an important role in this remote chlorination. 

Template-catalyzed remote chlorination reactions have also been examined in molecular complexes. In one early study (Scheme 24), ion pairing was used to hold a charged template near a chaig substrate. Selective catalyzed radical relay chlorination was observed, but the selectivity was not as good as has been seen when the template is covalently attached to the substrate. In more recent work better selectivity and some catalytic turnover has been observed. 

A well-known but relatively seldom used strategy for the selective functionalization of nonactivated centers is remote chlorination . In the first experiments the oxidizing reagent was covalently attached to a sterol as an ester. An improvement since has been the development of a true turnover catalyst by an ion-pair association procedure188. 

Selective chlorination of the 3-position of thietane 1,1-dioxide may be a consequence of hydrogen atom abstraction by a chlorine atom. Such reactions of chlorine atoms are believed to be influenced by polar effects, preferential hydrogen abstraction occurring remotely from an electron withdrawing group. The free radical chain reaction may be propagated by attack of the 3-thietanyl 1,1-dioxide radical on molecular chlorine. 

Interactions refers to any jobs, tasks, or operations carried out by people who could directly or indirectly cause the hazard to be released. Direct interactions with the plant might involve breaking open pipework, opening reactors, etc. Indirect interactions would include remote activation of valves from a control room, or the performance of maintenance on critical plant items. Errors that might occur during these interactions could allow the harm potential to be released. This could occur directly (for example, a worker could be overcome by a chlorine release if an incorrect valve line-up was made) or indirectly (for example, if a pump bearing in a critical cooling circuit was not lubricated, as in the example in Chapter 1). The procedure as described above... 

It is also interesting to note that quatemization of a chloropyrimi-dine at the nitrogen atom adjacent to the chloro group with methyl iodide results in the easy replacement of the chlorine by iodine, whereas similar salt formation on the remote nitrogen either leaves the chlorine unaffected or replacement occurs only at higher temperatures. A similar reaction occurs between 2-amino-6-chloro-4-methylpyrimidine and dimethyl sulfate in nitrobenzene to give the salt 45 and betaine 46. ... 

Most fish is still caught at sea and must be cooled soon after it is taken on board, and kept cold until it can be sold, frozen or otherwise processed [45]. The general practice is to put the fish into refrigerated sea water tanks, kept down to 0°C by direct expansion coils or a remote shell-and-tube evaporator. The sea water must be clean and maybe chlorine dosed. At this condition, fish can be kept for up to four days. 

The principles discussed in this chapter have a host of practical applications. Whenever you start your car, turn on your cell phone, or use a remote control for your television or other devices, you are making use of a voltaic cell. Many of our most important elements, including hydrogen and chlorine, are made in electrolytic cells. These applications, among others, are discussed in Section 18.6. ... 

A polar substituent, such as chlorine, stabilizes the transition states in which the incoming nucleophile and the polar group are remote (Figure 6, L = Cl). 

At the second stage of chlorine substitution in the tetramers there is a greater statistical probability for the incoming nucleophile to attack the phosphorus adjacent to =P(C1)(NHR), viz. P4 or P8, rather than the remote phosphorus, viz. P6 (Fig. 9). However, this statistical effect is countered by the electron releasing effect of the substituent already present on P2, which tends to deactivate P2 as well as P4 and P8 towards further nucleophilic substitution. It is observed that reactive amines such as dimethylamine (94) or ethylamine (95) react with N4P4C18 and... 

The product from chlorination of 4,4-dithiodimorpholine exploded violently after vacuum stripping of the solvent carbon tetrachloride. As it was a published process that previously had been operated uneventfully, no cause was apparent. It seems remotely possible that an unstable A-eh loro derivative could have been produced by N—S bond cleavage if chlorination conditions had differed from those previously employed. 

During preparation of chlorine by addition of the cone, acid to solid permanganate, a sharp explosion occurred on one occasion [1], Sulfuric acid was not used in error, nor was tube blockage involved [2], A similar incident was reported later [3], It appears remotely possible that permanganate may be able to oxidise chlorine to chlorine oxide [4], which as a dilute mixture with chlorine would be mildly explosive in the gas phase. 

Sanchez, J., M. Sole, and J. Albaiges. 1993. A comparison of distributions of PCB congeners and other chlorinated compounds in fishes from coastal areas and remote lakes. Inter. Jour. Environ. Anal. Chem. 50 269-284. 

Muir DC, Ford CA, Grift NP, et al. 1990. Geographic variation of chlorinated hydrocarbons in burbot (Lota lota) from remote lakes and rivers in Canada. Arch Environ Contam Toxicol 19(4) 530- 542. 

Hydrogen is also obtained as a by-product of brine electrolysis for the production of chlorine and sodium hydroxide. Small electrolytic plants (hydrogen generators) are often used for in situ applications when small quantities of hydrogen are required at remote locations. 

Dewulf, J., and H. Van Langenhove, Analytical Techniques for the Determination and Measurement Data of 7 Chlorinated Cr and C2-Hydrocarbons and 6 Monocyclic Aromatic Hydrocarbons in Remote Air Masses An Overview, Atmos. Environ., 31, 3291-3307 (1997). 

It has now been shown that a population inversion is not achieved between the aPi/2 and 2P% states of the chlorine atom in the vacuum ultraviolet flash photolysis of CF3C1,29 and thus the construction of a chlorine atom photodissociation laser appears remote at present. 

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