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Reactive Group Datasheet

Diazonium Salts

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There are 7 chemical datasheets assigned to this reactive group.


Many diazonium salts are highly explosive and decompose violently when heated.
Many diazonium salts are susceptible to displacement reactions by various substrates, generating nitrogen as a by-product. Another common reaction pathway is to undergo a coupling reaction to form a diazo compound. Diazonium salts in general are high energy materials that can decompose violently either by heating or by mechanical force (shock-sensitive), so in that sense, they may be considered self-reactive. A reaction enthalpy of -160 kJ/mol to -180 kJ/mol is associated with the diazo functional group. Stability often is improved by forming zinc chloride or other double salts. This has allowed some diazonium salts to be isolated safely in solid form. Complexation with crown ethers also has been shown to reduce or suppress thermal decomposition. Conversely, exposure to bases, transition metal impurities (e.g. Cu, Sn), nitrous acid and/or direct sunlight can promote decomposition and lower the onset temperature of decomposition.

There are various methods studied to remove diazonium compounds, but unfortunately there is no universal one. Adding an aqueous solution of hypophosphorous acid (H3PO2), in some cases in the presence of a catalyst (e.g. 0.05~0.10% Cu2+), is often suggested. For an intentional isolation of a diazonium salt, it must be considered hazardous and confined to a small scale. It is recommended that no more than 0.75 mmol of explosive diazonium salts should be handled at one time. The addition of other salts (e.g. ZnCl2) to form the so-called diazonium metal double salts or other compounds (e.g. 18-crown-6 ether) to form a crystalline complex can considerably stabilize the isolated diazonium salts. Furthermore, such diazonium salts should never be heated above 40°C and the dried powder should not be "scratched" with a metal spatula or ground finely (H. Zollinger, Diazotization of amines and dediazoniation of diazonium ions. In S. Patai, The Chemistry of Amino, Nitroso, Nitro and Related Groups, John Wiley & Sons, Ltd. (1996), 627).
Not widely studied.
Other Characteristics
Diazonium salts are common intermediates in organic syntheses. Given their undesirable physical properties (when concentrated, many are shock-sensitive and decompose violently with heating), they are not commonly isolated as final products. As intermediates, they are useful for preparing a number of aromatic derivatives and azo compounds. Common displacement reactions associated with aromatic diazonium salts include the Sandmeyer/Schiemann/Gattermann reactions to produce aryl halides, the Griess reaction to produce phenols, the Gomberg-Bachmann reaction to produce diaryl compounds, the Guttermann reaction to produce aryl nitro compounds, and the Meerwein reaction to produce aromatic alkenes.
Diazonium sulfates, diazonium sulfides, diazonium tetrahaloborates, diazonium triiodides, diazonium carboxylates, diazonium perchlorates.

Reactivity Documentation

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Mix Diazonium Salts with: