Unstable inorganic/organic anions

Generation and stabilization of unstable inorganic/organic anions in urea/thiourea complexes... 

Inorganic and organic anions can also be separated on cross-hnked polymers modified with cyclic ethers. Pioneering work in the field of adsorbing crown ethers onto chemically bonded reversed phases and PS-DVB polymers has been carried out by Kimura et al. The number of applicable crown ethers is limited because of their limited solubility and high price. Moreover, crown ether resins are mechanically unstable and are therefore operated with low flow rates, thus resulting in long analysis times. 

The onium carbanion formed under phase-transfer conditions is unstable depending on the anion source, and in the absence of an electrophilic reaction partner, degradation of the accumulated onium carbanion in the organic phase may be observed. This is known to proceed via Hoffman elimination, nucleophilic substitution and/or Stevens rearrangement (Scheme 1.4) [4f,6,7]. The direct decomposition of onium salt, as influenced by the strong inorganic base at the interface, may be also operative. 

Allophanate esters H2NCONHCOOR are among the oldest organic compounds recorded in the literature. The parent allophanic acid, H2NCONHCOOH, is not known in the free state, whereas inorganic allophanate salts are unstable and readily hydrolyzed by water to carbon dioxide, urea, and carbonate. However, the elusive allophanate anion can be generated in situ and stabilized in the following three inclusion compounds ... 

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