Chlorination with Chlorine

When chlorine dioxide is used for pulp bleaching in conjunction with the Kraft (sulfide) process for chemical pulping, by-product sodium sulfate can be used as a source of makeup sulfur and sodium consumed in the chemical cycle. The demand for sodium and sulfur in pulp bleaching is related to the loss of these chemicals through carryover in unbleached pulp. As process improvements have sought to reduce pollution from pulp mills, less sodium sulfate makeup is required. The trends in pulp bleaching to increase substitution of chlorine with chlorine dioxide have caused an oversupply of sodium sulfate, so that this by-product is often regarded as waste (81). 

Aromatic compounds may be chlorinated with chlorine in the presence of a catalyst such as iron, ferric chloride, or other Lewis acids. The halogenation reaction involves electrophilic displacement of the aromatic hydrogen by halogen. Introduction of a second chlorine atom into the monochloro aromatic stmcture leads to ortho and para substitution. The presence of a Lewis acid favors polarization of the chlorine molecule, thereby increasing its electrophilic character. Because the polarization does not lead to complete ionization, the reaction should be represented as shown in equation 26. 

In the second process the /z-paraffins are partially chlorinated with chlorine gas in a multistage reactor. The resulting product, a mixture of /z-paraffins and chloroparaffins, is fed, together with excess benzene, into a reactor where AlCl3-catalyzed alkylation is performed. The catalyst suspended or dissolved in the crude alkylate is then separated, while the benzene and unconverted ti-paraffins are recovered by distillation and recycled to the previous reaction stages. In the last step of the process, the LAB is separated from the heavy alkylates. This second process needs to be integrated with a chlorine production unit and with an additional industrial transformation plant which makes use of the corrosive HC1 byproduct. 

Dangerous materials may require special equipment. Chlorination with gaseous chlorine requires quite expensive storage facilities. Chlorination with chlorine, thionyl chloride, sulphuryl chloride, phosphorus oxychloride, phosphorus trichloride, or phosphorus pentachloride, all of which are fairly hazardous, requires off-gas treatment. Some of these reactants can be recycled. Pyrophoric solids such as hydrogenation catalysts, anhydrous aluminium trichloride for Friedel-Crafts reactions, or hydrides used as reducing agents should usually be handled using special facilities. Therefore, all of the above proce.sses are usually carried out in dedicated plants. 

Amino(trihalomethyl)methylenemalonates (1539) were chlorinated with chlorine in carbon tetrachloride, with /m-butyl hypochlorite in benzene, and phosphorus pentachloride or /V,/V-dichlorobenzenesulfonamide in dichloroethane (68ZOR1710 75ZOB873). Depending on the molar ratio, A-mono- or JV,./V-dichloro derivatives (1540, R2 = H, Cl) were obtained. 

Oxidation of triazine herbicides with chlorine and chlorine dioxide has been widely studied [105-108]. In the case of sulfur-containing triazines, oxidation occurs mainly via cleavage of the weakened R-S-CH3 bond rather than by addition of chlorine. Reactions of S-triazines with chlorine are faster than with chlorine dioxide, and form sulfoxide, sulfone, and a sulfone hydrolysis product. Chlorination with chlorine dioxide only produced sulfoxide [108]. Lopez et al. identified the formation of sulfonate esters during the chlorination of ametryn and terbutryn [106, 107]. Triazine DBFs identified by Brix et al. exhibited higher toxicities than the parent compounds [105]. Similar to triazines, clethodim, a cyclohexanedione herbicide, is oxidized by hypochlorite and chloramines to clethodim sulfoxide and then to sulfone [109]. 

On the contrary, when methylphenyldichlorosilane is chlorinated with chlorine in the presence of electrophilic catalysts (e.g. metals or their halo-genides), only the phenyl radical is chlorinated, while the methal radical is untouched. In this case chlorination develops in the following way ... 

Regarding ozonation processes, the treatment with ozone leads to halogen-free oxygenated compounds (except when bromide is present), mostly aldehydes, carboxylic acids, ketoacids, ketones, etc. [189]. The evolution of analytical techniques and their combined use have allowed some researchers to identify new ozone by-products. This is the case of the work of Richardson et al. [189,190] who combined mass spectrometry and infrared spectroscopy together with derivatization methods. These authors found numerous aldehydes, ketones, dicarbonyl compounds, carboxylic acids, aldo and keto acids, and nitriles from the ozonation of Mississippi River water with 2.7-3 mg L 1 of TOC and pH about 7.5. They also identified by-products from ozonated-chlorinated (with chlorine and chloramine) water. In these cases, they found haloalkanes, haloalkenes, halo aldehydes, haloketones, haloacids, brominated compounds due to the presence of bromide ion, etc. They observed a lower formation of halocompounds formed after ozone-chlorine or chloramine oxidations than after single chlorination or chlorami-nation, showing the beneficial effect of preozonation. 

Phenyl sulfonimidates5 or sulfonimidoyl fluorides6 are readily prepared from sulfonimidoyl chlorides, which are available in two steps from arenesulfinyl chlorides (Eq. 2). Treatment of the arenesulfinyl chloride with an amine and base (e.g., triethylamine) gives the corresponding sulfinamide which on chlorination with chlorine,5 rm-butyl hypochlorite,9 or A-chlorobenzotriazole10,11 gives the corresponding sulfonimidoyl chloride (Eq. 2). 

However, the process is more complex than this, and the usual molar ratio of chlorine dioxide to chlorine produced is about 1 1. The process is integrated with an electrolytic process for making the sodium chlorate, such that the liquor from the reduction step is recirculated to the electrolytic step. The product gas, a mixture of chlorine with chlorine dioxide, is washed with water, which preferentially dissolves the chlorine dioxide. The resulting solution is used for pulp bleaching. 

To reduce production of chlorinated organics during bleaching, the pulp and paper industry has replaced chlorine with chlorine dioxide. Chlorine dioxide or its primary precursor, sodium chlorate, can be produced by the low-tonnage chlorine industry with the same hardware that is used for synthesis of chlorine and hypochlorite. This simple transition from chlorine to chlorine dioxide synthesis may be the reason for the less-than-anticipated usage of hydrogen peroxide in the pulp and paper industry. Increasing use of chlorine dioxide could also lead to its applications in other effluent treatment areas such as industrial wastewater remediation. 

Aromatic amines, such as aniline, are easily chlorinated with chlorine water to give, for example, 2,4,6-trichloroaniline. 

Manufacture. First carbon tetrachloride, CClj, CClj2., is prepared by an alternate reaction between chloride and slake lime on acetylene. The carbon tetrachloride is then chlorinated with chlorine gas under light beams. 

Detection. A-chlorination with chlorine vapors and detection of the A-chloro derivatives as blue spots with iodide-o-tolidine solution. 

Polyolefin Tinuvin 144, 770 Hostavin TMN 20 Extraction with chloroform, polymer precipitation, evaporative concentration Alumina F254, 20 x 20 cm plate, 0.25-mm thickness 88/12, n-hexane/ ijo-propanol Chlorination with chlorine gas, sprayed with potassium iodide starch solution Sample size 10 pL [37]... 

Bromination of codeine results in 1-bromocodeine and finally in a tribromocompound chlorination with chlorine water is more complex and gives resinous products [1, 2], Apomorphine [m] is formed by heating morphine and concentrated hydrochloric acid in a sealed tube above 100° C., and, together with methyl chloride, from codeine under the same conditions [3-6] (see Chap. XXII). When codeine is heated on the water-bath with concentrated hydrochloric acid, however, replacement of the hydroxyl group by chlorine occurs and a-chlorocodide is produced [7-8] this may be prepared in other ways from codeine and i/r-oodeine, and can be isomerized to /3-chlorocodide, available directly from the isomers of codeine. The corresponding derivatives of morphine have been prepared. Bromocodide and bromomorphide may be prepared in like manner but cannot be isomerized, and an iodocodide results from the treatment of a-chloro- or bromocodide with potassium iodide. 

The electrophilic substitution of indoxazene-3-acetic acid and its derivatives has been investigated extensively. Chlorination with chlorine in acetic acid or with a slight excess of N-chlorosuccinimide produces a mixture of the a-chloroacetic acid (30 R1 = Cl, R2 = H) (48.6%) and 3-(dichloromethyl)-indoxazene (5%), whereas with a large excess of N-chlorosuccinimide a mixture of 3-(dichloromethyl)- and 3-(trichloromethyl)indoxazene results 47 Iodination with iodine monochloride in acetic acid, or bromination with an equivalent of bromine in the same medium, yields only the monohalogeno acids (30 R2 = H, R1 = I and Br, respectively).47-49 With an excess of bromine, 3-(tribromomethyl)indoxazene is formed.48 49 Surprisingly, bromination of the methyl ester (30 R1 = H, R2 = Me), even with an excess of... 

In general, methods similar to chlorination with chlorine and chlorides can be employed in the preparation of bromine derivatives. Because the reaction is milder, the bromination of the paraffin hydrocarbons does not, however, proceed so rapidly or to so great a degree and with the lower permissible operating temperature, the formation of polybromine compounds occurs to a lesser extent. 

The reaction of 2,3-dichloropropene with potassium thiocyanate and chlorination with chlorine or sulfuryl chloride leads directly to 2-chloro-5-(chloro-meth)d)thiazole (a). The reaction of 3-amino-2-chloropropene with ethyl for-... 

Chlorination with chlorine gas, sprayed with potassium iodide starch solution... 

Films of natural rubber latex were chlorinated with chlorine gas generated in situ from acidified hypochlorite solution at room temperature and characterised by FTIR/ ATR, SEM/EDX and contact angle measurements. The mechanism of the surface chlorination process of the films in aqueous solution is considered and the effect of chlorination on such properties as tackiness and hydrophilicity is discussed. (4th International Union of Materials Research Societies International Conference in Asia 97, Makuhari, Japan, 16-18 Sept.1997). 16 refs. 

Flufenerim (302) was prepared from 4,5-dichloro-6-ethylpyrimidine (347) (Scheme 82) [298]. Compound 370 was chlorinated with chlorine gas the product 371 thus obtained was subjected to nucleophilic substitution with AcOK to give acetate 372, which upon hydrolysis and subsequent reaction with diethylaminosul-phur trifluoride (DAST) gave fluoride 374. Finally, reaction of 374 with amine 375 led to the formation of Flufenerim (302). 

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