4- Chlorobenzenediazonium

Interaction of 2-, 3- or 4-chlorobenzenediazonium salts with (9-alkyldithiocarbon-ate ( xanthate ) solutions [8] or thiophenoxide solutions [9] produces explosive products, possibly arenediazo aryl sulfides. The intermediate diazonium xanthate produced during the preparation of m-thiocresol can be dangerously explosive under the wrong conditions [8], while the reaction of 3-nitrobenzenediazonium chloride with xanthate solution at 70—75°C proceeds with near-explosive evolution of nitrogen [4]. The product of interaction of 2-chlorobenzenediazonium chloride and sodium 2-chlorothiophenoxide exploded violently on heating to 100°C, and the oil... 

The azo coupling reaction proceeds by the electrophilic aromatic substitution mechanism. In the case of 4-chlorobenzenediazonium compound with l-naphthol-4-sulfonic acid [84-87-7] the reaction is not base-catalyzed, but that with l-naphthol-3-sulfonic acid and 2-naphthol-8-sulfonic acid [92-40-0] is moderately and strongly base-catalyzed, respectively. The different rates of reaction agree with kinetic studies of hydrogen isotope effects in coupling components. The magnitude of the isotope effect increases with increased steric hindrance at the coupler reaction site. The addition of bases, even if pH is not changed, can affect the reaction rate. In polar aprotic media, reaction rate is different with alkyl-ammonium ions. Cationic, anionic, and nonionic surfactants can also influence the reaction rate (27). 

The dediazoniation of 4-chlorobenzenediazonium tetrafluoroborate in HCO / CO2- buffers can be cited as an example (Schwarz and Zollinger, 1981 Besse and... 

On the basis of the nucleophilicity parameters B, NBs, and fi (see Table 8-2) one expects less of the homolytic product in water than in methanol. This is, however, not the case. It has been known for many decades that a very complex mixture of products is formed in the decomposition of diazonium ions, including polymeric products, the so-called diazo tars. In alcohols this is quite different. The number of products exceeds three or four only in exceptional cases, diazo tars are hardly formed. For dediazoniation in weakly alkaline aqueous solutions, there has, to the best of our knowledge, been only one detailed study (Besse et al., 1981) on the products of decomposition of 4-chlorobenzenediazonium fluoroborate in aqueous HCOf/ CO]- buffers at pH 9.00-10.30. Depending on reaction conditions, up to ten compounds of low molecular mass were identified besides the diazo tar. 

The kinetics of the decomposition of the 4-chlorobenzenediazonium ion under strict exclusion of oxygen (< 5 ppb 02, Schwarz and Zollinger, 1981) are compatible with the CIDNP results, subject to the reservation mentioned already, namely that CIDNP as a probe does not necessarily give results for all pathways, whereas kinetic measurements are normally related to the sum of all competitive mechanisms. The first reaction observable with conventional kinetic methods is the formation of the (E )-diazoate (t1/2 ca. 200 min), but it is also first-order with respect to the diazonium ion concentration. 

Packer et al. (1981) found that y-irradiation reduces arenediazonium tetrafluoro-borates to aryl radicals. Packer and Taylor (1985) investigated the y-irradiation of 4-chlorobenzenediazonium tetrafluoroborate by a 60Co source in the presence of 1 alone or I- +13 . The major product in the presence of iodide was 4,4 -dichloroazo-benzene. With I- + 1 ", however, it was 4-chloroiodobenzene. Two other investigations of the reactivity of aryl radicals with iodine-containing species are important for the understanding of the chain process of iodo-de-diazoniation that starts after formation of the aryl radical. Kryger et al. (1977) showed that, in the thermal decomposition of phenylazotriphenylmethane, the rate of iodine abstraction from I2 is extremely fast (see also Ando, 1978, p. 341). Furthermore, evidence for the formation of the radical anion V2 was reported by Beckwith and Meijs (1987) and by Abey-wickrema and Beckwith (1987) (see Sec. 10.11). 

Stronger reducing agents than Cu1 can be used for reactions that are related to the classical Meerwein reaction. Tim salts not only catalyze the formation of aryl radicals from diazonium ions but, as shown by Citterio and Vismara (1980) and Cit-terio et al. (1982 a), in stoichiometric proportions they also reduce the primary aryl-ethane radical to the arylethyl anion, which is finally protonated by the solvent SH (Scheme 10-61). This method is the subject of a contribution to Organic Syntheses (Citterio, 1990), in which 4-(4 -chlorophenyl)buten-2-one is obtained in 65-75% yield from 4-chlorobenzenediazonium chloride and but-3-en-2-one. 

Kuokkanen (1985) determined complexation constants for 4-tert-butyl- and 4-chlorobenzenediazonium tetrafluoroborate with polyethylene glycols of average molecular mass 300, 600, 1000, and 2000 under the same experimental conditions as mentioned above. The constants are significantly lower than those with... 

Bagal et al. (1975) investigated in more detail the role of donor-acceptor complexes in the azo coupling reaction of the 4-nitrobenzenediazonium ion with 2-naphthylamine-3,6-disulfonic acid and that of the 4-chlorobenzenediazonium ion with 2-naphthol-6-sulfonic acid. Their kinetic results are, as would be expected, compatible with the mechanisms shown in Schemes 12-74 or 12-75. 

Besides two older examples of classical Meerwein reactions156, there is a more recent description of the reaction of 4-chlorobenzenediazonium chloride with but-3-en-2-one, catalyzed by Tinl in stoichiometric proportions. This method was developed by Citterio and gives 4-(4 -chlorophenyl)but-3-en-2-one in 65-75% yield. 

There is a long history of the preparation of explosive solids or oils from interaction of diazonium salts with solutions of various sulfides and related derivatives. Such products have arisen from benzene- and toluene-diazonium salts with hydrogen, ammonium, or sodium sulfides [1,5] 2- or 3-chlorobenzene-, 4-chloro-2-methylbenzene-, 2- or 4-nitrobenzene- or 1- or 2-naphthalene-diazonium solutions with hydrogen sulfide, sodium hydrogen sulfide or sodium mono-, di- or poly-sulfides [l]-[4,7], 4-Bromobenzenediazonium solutions gave with hydrogen sulfide at -5°C a product which exploded under water at 0°C [2], and every addition of a drop of 3-chlorobenzenediazonium solution to sodium disulfide solution... 

Chlorobenzenediazonium triiodide, 2137 2,4-Dimethylbenzenediazonium triiodide, 2963 2- or 4-Methoxybenzenediazonium triiodide, 2758 4-Toluenediazonium triiodide, 2756 See other diazonium salts, iodine compounds... 

The Gomberg coupling reaction of aryl diazonium salts with arenes is catalysed by quaternary ammonium salts [49], Although yields are variable, they are generally >50% [49, 50]. When aromatic solvents other than benzene are used, the appropriate biaryls are produced, e.g. 4-chlorobenzenediazonium tetrafluoroborate reacts with chlorobenzene to produce the 2,4 -, 3,4 - and 4,4 -dichlorobiphenyls in a ca. 67 18 15 ratio. 

N 37.75% yel crysts(from ale), reported as brn solid by Bekhli et al(Ref 4), mp-dec at 136-4 0° on heating slowly, explodes mildly on heating rapidly between 15 0-60° was first prepd by Walther Grieshammer (Refs 1 2) from reaction of 4 Chlorobenzenediazonium chloride dicyanodiamide in alk soln. It was later prepd by others (Refs 3, 4, 5 6).Some of its salts are mild expls Refs l)Beil 16, (4 05) 2)R. von Walther ... 

Note. (1) The 4-chlorobenzenediazonium fluoroborate may be prepared using the conditions described for p-methoxybenzenediazonium fluoroborate, Expt 6.77, p-fluoroanisole. This methoxy derivative could also be used in the above preparation to give 4-methoxybiphenyl, m.p. 89 °C. 

Chloro- 1,4-benzenediamine, 2342 4-Chloro- 1,2-benzenediamine, 2340 4-Chloro- 1,3-benzenediamine, 2341 4-Chlorobenzenediazonium triiodide, 2130 4-Chlorobenzenesulfonyl azide, 2145... 

---