Dichlorine production

In chlorinations either a substitution or an addition process can occur with the ultimate reaction pathway(s) determined by a combination of factors, which include the reaction conditions, the positions and natures of any substituents present, and the catalyst used. Uncatalyzed chlorination of benzothiadiazole is an exothermic reaction that gives rise to a mixture of isomeric tetrachloro addition products. These are converted in basic medium into 4,7-dichloro-2,1,3-benzothiadiazole (70RCR923). When an iron(III) catalyst is present 4- and 7-chloro substitution becomes the dominant process. Chlorination of a number of 4-substituted 2,1,3-benzothiadiazoles (43) using an oxidative process gave a combination of chlorinated and oxidized products. The 4-hydroxy, 4-amino-, 4-methyl-amino, and 4-acetoxy derivatives of 43 all formed the chloroquinones (44) (40-61% yields). With the 4-aIkoxy substrates both 44 and some 5,7-dichlorinated product were obtained (88CHE96). 

This mixture is fed into bubble columns and contacted with chlorine gas at 3.5 bar and 115-145 °C [57]. A typical reaction mixture has a composition of 38.5% acetic acid, 11.5% acetic anhydride and 50% chlorine gas. The crude product is first purified by distillation. Thereafter, either crystallization or hydrogen reduction at a Pd catalyst is conducted to separate the monochlorinated from the dichlorinated product. 

Boyes and Wild reported the manganese-mediated regioselective chlorination of allenes [14]. For the dichlorination of cyclo-l,2-nonadiene, the dichloride was obtained as the major product whereas the reaction of monosubstituted allene afforded a mixture of regiosomers of the dichlorination products with 2,3-dichloro-1-alkene 12 being the major one. The yield with oxalyl chloride is better than that with TMSC1. 

The present procedure represents a modification of two previously published procedures,2 3 and results in a safer, more convenient preparation of the title compound. In Step A, the ratio of reagents has been adjusted to allow for the formation of only pentaerythrityl tetrachloride and trichlorohydrin none of the dichlorinated product is produced. Thus work up of the reaction is easier the product can be filtered rather than extracted, so minimal solvent is used, and the crude products are used in Step B, thus avoiding a tedious distillation. Step B has also been modified to make it safer and more convenient. The crude material from Step A is used, and addition of nitric acid over a longer period reduces the hazards of this step. Previously, it was noted that after the nitric acid was added in one portion and the mixture was heated, "a reaction became apparent, whereupon the flask was lowered rapidly into a waiting cold bath and the operator withdrew. 2 Step C is a more detailed modification of the procedure reported by the Russian workers3 as an improvement to the original method of Mooradian and Cloke.2 The latter used quinoline to catalyze the conversion of tris(chloromethyl)acetic acid to 3-chloro-2-(chloromethyl)propene. 

Alkylbenzenes undergo free-radical halogenation much more easily than alkanes because abstraction of a hydrogen atom at a benzylic position gives a resonance-stabilized benzylic radical. For example, ethylbenzene reacts with chlorine in the presence of light to give cr-chlon >e thy I benzene. Further chlorination can occur to give a dichlorinated product. 

When ethylene carbonate is partly chlorinated, the two dichlorinated products (III) and (IV) formed cannot be separated by distillation and an 85 15 mixture of (III) (IV) only is available commercially. 

Chlorination of dicyclopropyl sulfone was carried out by successive treatment with butyllithium and AT-chlorosuccinimide to give a mixture of mono- and dichlorinated products 4 and 5. ... 

To obtain the composition at a much later time we choose [B] = 0.001. Then, proceeding in the same manner, we find most of the product to be mono- and di-chlorobenzene, with a little trichlorobenzene substituted product. The results for a range of [Cl2] up to 2.14 are summarized in Table 2-11. Note that the maximum yield of monochlorinated product is obtained when approximately 1 mole of Clj has been reacted, and the maximum yield of dichlorinated product results when about 2 moles of CI2 have been reacted. Selectivities for any two products can easily be found by taking ratios of the yields, Eq. (2-90). Since the problem has been solved on a basis of 1 mole of initial benzene, [M], [D], [7] also are equivalent to mole fractions. 

Allylic sulfones/ hexachloroethane or CCI4 Mono or dichlorinated products Phase-transfer catalyst High yields 52... 

When genistein and biochanin-A react with physiologic concentrations of HOCl, mono-and dichlorinated products can be detected. Daidzein forms only a monochlorinated metabolite. I en genistein and daidzein react with ONOO, mononitrated derivatives were detected. However, biochmin-A did not react with ONOOY20 . 

Scheme 42.26). A highly enantioselective dichlorination of 90 was used as one of the key steps. A total of 4 equivalences of 91 was treated with BH3 THF and AcOH, followed by the addition of 90 to yield the dichlorinated product 92 in 93% yield and 87% ee. A borate complex was proposed as the product-determining intermediate. The authors also proposed that the chiral ligands possess dual roles one would be to form a iT-stacking interaction with the substrate, while the other would be to orientate the trajectory of chlorine. 

Hence, if (C1)<46.4%, two types of structural units exist, both non-chlorinated and monochlorinated but if 46.4% < o(Cl) < 64%, then both mono- and dichlorinated products are formed. In the present case (Figure 60), o(Cl) = 54.6% can be introduced into PP film during 4 hours of continuous chlorination, which corresponds to TV (Cl) = 1.376 per structural unit, supposing that chlorination proceeds uniformly in the whole volume of PP film. Despite small film thickness, this is not completely true (as well as all above-described heterogeneous transformations) however, it is warranted by the fact that the refractive index change is measured interferometrically along the whole optical thickness of the film. Real saturation at o(Cl) = 54.6% (instead of o(Cl) = 70% according to [140]) is explained by the weakly developed surface of film PP samples. 

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