Über die Bildung von Azoverbindungen bei der Zersetzungsreaktion aromatischer Diazoverbindungen in wässrigem Medium

Matrka, M.; Ságner, Z.; Chmátal, V.; Štěrba, V.; Veselý, M.

doi:10.1135/cccc19671462

Cited by 8 publications

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“…2) In water, the rate of dediazoniations increases if the pH is raised from 3 (or lower) to the range 8-11 [26] [27].…”

mentioning

confidence: 99%

Dediazoniation of Arenediazonium Ions in Homogeneous Solution. Part XII. Solvent effects in competitive heterolytic and homolytic dediazoniations

Szele¹,

Zollinger²

1978

Helvetica Chimica Acta

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SummaryIn heterolytic dediazoniations arenediazonium salts form aryl cations. The reaction rates are relatively slow; they depend only to a small extent on the solvent. It is shown that the solvents in which the heterolytic dediazoniation mechanism is predominant have a low nucleophilicity, whereas in solvents of high nucleophilicity homolysis of arenediazonium salts, i.e. the formation of aryl radicals and related intermediates, is favoured. Under comparable conditions, homolytic rates are faster than the corresponding rates of heterolysis. Homolysis is strongly enhanced by addition of nucleophiles which form relatively stable radicals by electron transfer. The ability of additives to catalyze homolysis of arenediazonium salts can be explained using the concept of a nucleofugic3) homolytic leaving group.

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“…2) In water, the rate of dediazoniations increases if the pH is raised from 3 (or lower) to the range 8-11 [26] [27].…”

mentioning

confidence: 99%

Dediazoniation of Arenediazonium Ions in Homogeneous Solution. Part XII. Solvent effects in competitive heterolytic and homolytic dediazoniations

Szele¹,

Zollinger²

1978

Helvetica Chimica Acta

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“…A particularly clear case of such a maximum was reported by Stgrba et al [9] for the reaction of 4-chloro-2-nitrobenzenediazonium ions (4) measured in aqueous buffer solutions between pH 2.0 and 8.0 (rate maximum at ca. pH 6.5).…”

Section: Discussionmentioning

confidence: 86%

“…Kinetics. Ste'rba et al [9] report a plot of their rate constants for the hydrolysis of 4 as a function of pH at 30°, but give no numerical figures for these constants nor any information on the buffers used. We measured therefore these rates, first in citric acid/phosphate buffers between pH 2.90 and 7.90, then in H2POJHPOf, acetate and propionate buffers, always at ionic strength I=0.5.…”

Section: 'mentioning

confidence: 98%

Nucleophilic Aromatic Substitutions. Part XIV.. Investigation of the mechanism of hydroxy‐denitration of 4,2‐and 2,4‐chloronitrobenzenediazonium ions as a function of pH

Pikulik¹,

Weber²,

Zollinger³

1981

Helvetica Chimica Acta

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Summary4,2-Chloronitrobenzenediazonium ions in aqueous buffer solutions between pH 2.9 and 7.9 do not hydrolyze by dediazoniation as previous authors have assumed, but by denitration. The isomeric 2,4-compound reacts by denitration (ca. 70%) and dechlorination (ca. 30%). The reactions are general base catalyzed. The products and kinetics are consistent with an S,Ar-mechanism in which the general base-catalyzed addition of a hydroxyl group at the reacting C-atom is rate-limiting. The rate maxima at or near the pH-values corresponding to (pK, + pK2)/2 of the diazonium cis-diazotate equilibria can be rationalized on the assumption that the diazonium ion is the only equilibrium form of the diazo compound which enters the substitution proper, and the superposition of rate term ;,k, [B] of all nucleophiles involved (HzO, OH-and buffer bases).

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Sodium Nitrite

McCullough

Bessieres

2005

Encyclopedia of Reagents for Organic Synthesis

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Über die Bildung von Azoverbindungen bei der Zersetzungsreaktion aromatischer Diazoverbindungen in wässrigem Medium

Cited by 8 publications

References 0 publications

Dediazoniation of Arenediazonium Ions in Homogeneous Solution. Part XII. Solvent effects in competitive heterolytic and homolytic dediazoniations

Dediazoniation of Arenediazonium Ions in Homogeneous Solution. Part XII. Solvent effects in competitive heterolytic and homolytic dediazoniations

Nucleophilic Aromatic Substitutions. Part XIV.. Investigation of the mechanism of hydroxy‐denitration of 4,2‐and 2,4‐chloronitrobenzenediazonium ions as a function of pH

Sodium Nitrite

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