Salicylaldoxime

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Salicylaldoxime
Salicylaldoxime.png
Identifiers
CAS number 94-67-7 YesY
PubChem 5359280
ChemSpider 10446269 YesY
Jmol-3D images Image 1
Properties
Molecular formula C7H7NO2
Molar mass 137.14 g mol−1
Appearance white to off-white crystals
Melting point 59 to 61 °C (138 to 142 °F; 332 to 334 K)
Solubility in water 25 g L-1
Hazards
NFPA 704
Flammability code 1: Must be pre-heated before ignition can occur. Flash point over 93 °C (200 °F). E.g., canola oil Health code 2: Intense or continued but not chronic exposure could cause temporary incapacitation or possible residual injury. E.g., chloroform Reactivity code 0: Normally stable, even under fire exposure conditions, and is not reactive with water. E.g., liquid nitrogen Special hazards (white): no codeNFPA 704 four-colored diamond
Except where noted otherwise, data are given for materials in their standard state (at 25 °C (77 °F), 100 kPa)
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Infobox references

Salicylaldoxime is an organic compound described by the formula C6H4CH=NOH-2-OH. It is the oxime of salicylaldehyde. This crystalline, colorless solid is a chelator and sometimes used in the analysis of samples containing transition metal ions, with which it often forms brightly coloured coordination complexes.[1]

Reactions[edit]

Salicylaldoxime is the conjugate acid of a bidentate ligand:

2 C6H4CH=NOH-2-OH + Cu2+ → Cu(C6H4CH=NOH-2-OH)2 + 2 H+

In highly acidic media, the ligand decomplexes and the metal aqua complex is liberated. In this way the ligand is used as a recyclable extractant. It typically forms charge-neutral complexes with divalent metal ions.

Analytical chemistry[edit]

In the era when metals were analysed by spectrophotometry, many chelating ligands were developed that selectively formed brightly coloured complexes with particular metal ions. This methodology has been eclipsed with the introduction of inductively coupled plasma methodology. Salicylaldoxime can be used to selectively precipitate metal ions for gravimetric determination. It forms a greenish-yellow precipitate with copper at a pH of 2.6 in the presence of acetic 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 in ion selective electrodes, with good response to Pb2+ and Ni2+.[3]

Structure of the copper(II) complex of the conjugate base of salicylaldoxime. Notice that the hydroxyl groups form hydrogen bonds to the coordinated phenolate centers.

Extraction of metals[edit]

Saloximes are used in the extraction and separation of metals from their ores. In one application of hydrometallurgy, Cu2+ is extracted into organic solvents as its saloxime complex..[4]

External links[edit]

References[edit]

  1. ^ P Sedwick; D Shinn; H Zeitlin (1984). "The Separation Of Metals From Treated Deep-Sea Ferromanganese Nodules By Adsorptive Bubble Techniques Using Salicylaldoxime And Sodium Diethyldithiocarbamate As Organic Precipitating Reagents". Separation Science and Technology 19 (2–3): 183–190. doi:10.1080/01496398408060654. 
  2. ^ 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. 
  3. ^ EK Quagraine; VPY Gadzekpo (December 1992). "Studies Of Spectrophotometric Reagents In Some Transition-Metal And Lead Ion-Selective Electrodes". Analyst 117 (12): 1899–1903. doi:10.1039/an9921701899. 
  4. ^ Peter A. Tasker, Christine C. Tong, Arjan N. Westra "Co-extraction of cations and anions in base metal recovery" Coordination Chemistry Reviews 2007, vol. 251, pp. 1868–1877. doi:10.1016/j.ccr.2007.03.014