Salicylaldoxime is anorganic compound described by the formula C6H4CH=NOH-2-OH. It is theoxime ofsalicylaldehyde. This crystalline, colorless solid is achelator and sometimes used in the analysis of samples containingtransition metalions, with which it often forms brightly colouredcoordination complexes.[1]
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| Names | |
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| IUPAC name Salicylaldehyde oxime | |
| Other names Saldox; 2-[(E)-(hydroxyimino)methyl]phenol | |
| Identifiers | |
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3D model (JSmol) | |
| ChemSpider |
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| ECHA InfoCard | 100.002.140 |
| UNII | |
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| Properties | |
| C7H7NO2 | |
| Molar mass | 137.138 g·mol−1 |
| Appearance | white to off-white crystals |
| Melting point | 59 to 61 °C (138 to 142 °F; 332 to 334 K) |
| 25 g L−1 | |
| Hazards | |
| NFPA 704 (fire diamond) | |
Except where otherwise noted, data are given for materials in theirstandard state (at 25 °C [77 °F], 100 kPa). | |
Reactions
editSalicylaldoxime is the conjugate acid of a bidentate ligand:
- 2 C6H4CH=NOH-2-OH + Cu2+ → Cu(C6H4CH=NOH-2-O)2 + 2 H+
In highly acidic media, the ligand protonates, and themetal aquo complex and aldoxime are liberated. In this way the ligand is used as a recyclable extractant.It typically forms charge-neutral complexes with divalent metal ions.
Analytical chemistry
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In the era when metals were analysed byspectrophotometry, many chelatingligands were developed that selectively formed brightly coloured complexes with particular metal ions. This methodology has been eclipsed with the introduction ofinductively coupled plasma methodology. Salicylaldoxime can be used to selectivelyprecipitate metal ions forgravimetric determination. It forms a greenish-yellow precipitate with copper at apH of 2.6 in the presence ofacetic acid. Under these conditions, this is the only metal that precipitates; at pH 3.3,nickel also precipitates. Iron (III) will interfere.[2] It has been used as an ionophore inion selective electrodes, with good response to Pb2+ and Ni2+.[3]
Extraction of metals
editSaloximes are used in the extraction and separation of metals from their ores. In one application ofhydrometallurgy, Cu2+ is extracted into organic solvents as its saloxime complex.[4]
References
edit- ^Smith, Andrew G.; Tasker, Peter A.; White, David J. "The structures of phenolic oximes and their complexes" Coordination Chemistry Reviews 2003, volume24, pp. 61-85.doi:10.1016/S0010-8545(02)00310-7
- ^SH Simonsen; HM Burnett (1955). "Spectrophotometric Determination Of Copper With Salicylaldoxime - Application To Analysis Of Aluminum Alloys".Analytical Chemistry.27 (8):1336–1339.doi:10.1021/ac60104a039.
- ^EK Quagraine; VPY Gadzekpo (December 1992). "Studies Of Spectrophotometric Reagents In Some Transition-Metal And Lead Ion-Selective Electrodes".Analyst.117 (12):1899–1903.Bibcode:1992Ana...117.1899Q.doi:10.1039/an9921701899.
- ^Tasker, Peter A.; Tong, Christine C.; Westra, Arjan N. (2007). "Co-extraction of Cations and Anions in Base Metal Recovery".Coordination Chemistry Reviews.251 (13–14):1868–1877.doi:10.1016/j.ccr.2007.03.014.