Uranyl acetate

Uranyl acetate is the acetate salt of uranium oxide, a toxic yellow-green powder useful in certain laboratory tests. Structurally, it is a coordination polymer with formula UO2(CH3CO2)2(H2O)·H2O.

Uranyl acetate
Uranyl acetate

Hydrated crystal structure
Names
IUPAC name
Uranium bis((acetato)-O)dioxo-dihydrate
Other names
Uranyl ethanoate; Uranyl acetate dihydrate
Identifiers
3D model (JSmol)
ChemSpider
ECHA InfoCard 100.007.971
EC Number
  • (anhydrous): 208-767-5
UNII
  • (anhydrous): InChI=1S/2C2H4O2.2O.U/c2*1-2(3)4;;;/h2*1H3,(H,3,4);;;
    Key: IXSMFXMQHOBORU-UHFFFAOYSA-N
  • (dihydrate): InChI=1S/2C2H4O2.2H2O.2O.U/c2*1-2(3)4;;;;;/h2*1H3,(H,3,4);2*1H2;;;/q;;;;;;+2/p-2
    Key: VVAHPLNXWRLLIG-UHFFFAOYSA-L
  • (anhydrous) ionic form (anhydrate): O=C(C)[O-].[O+]#[U]#[O+].O=C(C)[O-]
  • (dihydrate): CC(=O)[O-].CC(=O)[O-].O.O.O=[U+2]=O
  • coordination dimer (hydrate): [o+]0c(C)o[U-5]01(#[O+])(#[O+])([O+H2])[o+]c(C)o[U-5]0([o+]c(C)o0)(#[O+])(#[O+])([O+H2])[o+]c(C)o1
  • coordination dimer (anhydrous): [o+]0c(C)o[U-4]01(#[O+])(#[O+])[o+]c(C)o[U-4]0([o+]c(C)o0)(#[O+])(#[O+])[o+]c(C)o1
Properties
UO2(CH3COO)2 (anhydrous)
UO2(CH3COO)2·2H2O (dihydrate)
Molar mass 424.146 g/mol (dihydrate)
Appearance yellow-green crystals (dihydrate)
Density 2.89 g/cm3 (dihydrate)
Melting point decomposes at 80 °C (dihydrate)
7-8 g/100 ml
Solubility slightly soluble in ethanol[1]
Hazards
GHS labelling:
GHS06: ToxicGHS08: Health hazardGHS09: Environmental hazard
Danger
H300, H330, H373, H411
P260, P264, P270, P271, P273, P284, P301+P310, P304+P340, P310, P314, P320, P321, P330, P391, P403+P233, P405, P501
Safety data sheet (SDS) External MSDS
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Infobox references

Structure

In the polymer, uranyl (UO22+) centers are bridged by acetate ligands. The remainder of each (heptacoordinate) coordination sphere is provided by an aquo ligand and a bidentate acetate ligand. One water of crystallization occupies the lattice.[2]

Uses

Uranyl acetate is extensively used as a negative stain in electron microscopy.[3] Most procedures in electron microscopy for biology require the use of uranyl acetate. Negative staining protocols typically treat the sample with 1% to 5% aqueous solution. Uranyl acetate staining is simple and quick to perform and one can examine the sample within a few minutes after staining. Some biological samples are not amenable to uranyl acetate staining and, in these cases, alternative staining techniques and or low-voltage electron microscopy technique may be more suitable.

1% and 2% uranyl acetate solutions are used as an indicator, and a titrant in stronger concentrations in analytical chemistry, as it forms an insoluble salt with sodium (the vast majority of sodium salts are water-soluble). Uranyl acetate solutions show evidence of being sensitive to light, especially UV, and will precipitate if exposed.

Uranyl acetate is also used in a standard test—American Association of State Highway and Transportation Officials (AASHTO) Designation T 299—for alkali-silica reactivity in aggregates (crushed stone or gravel) being considered for use in cement concrete.

Uranyl acetate dihydrate has been used as a starting reagent in experimental inorganic chemistry.[4]

Uranyl carboxylates are known for diverse carboxylic acids (formate, butyrate, acrylate).[5]

Safety

Uranyl acetate is both radioactive and toxic. Normal commercial stocks prepared from depleted uranium have a typical specific activity of 0.37–0.51 microcuries (14–19 kBq) per gram. This mild level of radioactivity is insufficient to be harmful while the material remains external to the body. However, this reason has still lead others to find alternatives, such as neodymium acetate,[6] platinum blue[7][8][9][10] and oolong tea extracts.[11][12]

Uranyl acetate is very toxic if ingested, inhaled as dust or by skin contact if skin is cut or abraded. The toxicity is due to the combined effect of chemical toxicity and mild radioactivity and there is a danger of cumulative effects from long term exposure.

Uranium salts are predominantly nephrotoxic.

References
  1. Lide, David R. (1998), Handbook of Chemistry and Physics (87 ed.), Boca Raton, FL: CRC Press, pp. 3–566, ISBN 0-8493-0594-2
  2. Howatson, J.; Grev, D.M.; Morosin, B. (1975). "Crystal and molecular structure of uranyl acetate dihydrate". Journal of Inorganic and Nuclear Chemistry. 37 (9): 1933–1935. doi:10.1016/0022-1902(75)80918-3.
  3. "Negative Staining" University of Oxford
  4. Sessler, Jonathan L.; Seidel, Daniel; Vivian, Anne E.; Lynch, Vincent; Scott, Brian L.; Keogh, D. Webster (2001). "Hexaphyrin(1.0.1.0.0.0): An Expanded Porphyrin Ligand for the Actinide Cations Uranyl (UO22+) and Neptunyl (NpO2+)". Angewandte Chemie International Edition. 40 (3): 591–594. doi:10.1002/1521-3773(20010202)40:3<591::AID-ANIE591>3.0.CO;2-0.
  5. Klepov, Vladislav V.; Vologzhanina, Anna V.; Alekseev, Evgeny V.; Pushkin, Denis V.; Serezhkina, Larisa B.; Sergeeva, Olga A.; Knyazev, Aleksandr V.; Serezhkin, Viktor N. (2016). "Structural diversity of uranyl acrylates". CrystEngComm. 18 (10): 1723–1731. doi:10.1039/C5CE01957E.
  6. Kuipers, Jeroen; Giepmans, Ben N. G. (1 April 2020). "Neodymium as an alternative contrast for uranium in electron microscopy". Histochemistry and Cell Biology. 153 (4): 271–277. doi:10.1007/s00418-020-01846-0. ISSN 1432-119X. PMC 7160090. PMID 32008069.
  7. Hosogi N, Nishioka H, Nakakoshi M (2015) Evaluation of lanthanide salts as alternative stains to uranyl acetate. Microscopy (Oxf) 64:429–435
  8. Ikeda K, Inoue K, Kanematsu S, Horiuchi Y, Park P (2011) Enhanced effects of nonisotopic hafnium chloride in methanol as a substitute for uranyl acetate in TEM contrast of ultrastructure of fungal and plant cells. Microsc Res Tech 74:825–830
  9. Inaga S, Katsumoto T, Tanaka K, Kameie T, Nakane H, Naguro T (2007) Platinum blue as an alternative to uranyl acetate for staining in transmission electron microscopy. Arch Histol Cytol 70:43–49
  10. Yamaguchi K, Suzuki K, Tanaka K (2010) Examination of electron stains as a substitute for uranyl acetate for the ultrathin sections of bacterial cells. J Electron Microsc (Tokyo) 59:113–118
  11. Sato S, Adachi A, Sasaki Y, Ghazizadeh M (2008) Oolong tea extract as a substitute for uranyl acetate in staining of ultrathin sections. J Microsc 229:17–20
  12. He X, Liu B (2017) Oolong tea extract as a substitute for uranyl acetate in staining of ultrathin sections based on examples of animal tissues for transmission electron microscopy. J Microsc 267:27–33
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