Lead(IV) acetate
Organometallic compound (Pb(C2H3O2)4)
From Wikipedia, the free encyclopedia
Lead(IV) acetate or lead tetraacetate is an metalorganic compound with chemical formula (CH3CO2)4Pb, often abbreviated as Pb(OAc)4, where Ac is acetyl. It is a colorless solid that is soluble in nonpolar, organic solvents, indicating that it is not a salt. It is degraded by moisture and is typically stored with additional acetic acid. The compound is used in organic synthesis.[2]
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| Names | |
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| IUPAC name
Lead(IV) acetate | |
| Systematic IUPAC name
Tetrakis(acetyloxy)plumbane | |
| Other names
Lead tetraacetate Plumbic acetate | |
| Identifiers | |
3D model (JSmol) |
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| ChEBI | |
| ChemSpider | |
| ECHA InfoCard | 100.008.099 |
| EC Number |
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PubChem CID |
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| UNII | |
CompTox Dashboard (EPA) |
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| Properties | |
| (CH3CO2)4Pb | |
| Molar mass | 443.376 g/mol |
| Appearance | colorless or pink columnar crystals |
| Odor | vinegar |
| Density | 2.228 g/cm3 (17 °C) |
| Melting point | 175 °C (347 °F; 448 K) |
| Boiling point | decomposes |
| soluble, reversible hydrolysis | |
| Solubility | Reacts with ethanol. Soluble in chloroform, benzene, nitrobenzene, hot acetic acid, HCl(aq), tetrachloroethane. |
| Hazards | |
| Occupational safety and health (OHS/OSH): | |
Main hazards |
Toxic |
| GHS labelling:[1] | |
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| Danger | |
| NFPA 704 (fire diamond) | |
| Related compounds | |
Related compounds |
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Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Structure
In the solid state the lead(IV) centers are coordinated by four acetate ions, which are bidentate, each coordinating via two oxygen atoms. The lead atom is 8 coordinate and the O atoms form a flattened trigonal dodecahedron.[3]
Preparation
It is typically prepared by treating of red lead with acetic acid and acetic anhydride (Ac2O), which absorbs water. The net reaction is shown:[4][5]
- Pb3O4 + 4 Ac2O → Pb(OAc)4 + 2 Pb(OAc)2
The remaining lead(II) acetate can be partially oxidized to the tetraacetate by Cl2, with a PbCl2 by-product:
- 2 Pb(OAc)2 + Cl2 → Pb(OAc)4 + PbCl2
Reagent in organic chemistry
Lead tetraacetate is a strong oxidizing agent,[6] a source of acetyloxy groups, and a general reagent for the preparation of organolead compounds. Some of its many uses in organic chemistry:
- Acetoxylation of benzylic, allylic,[7] and α-oxygen ether C−H bonds, for example the conversion of dioxane to 2-acetoxy-1,4-dioxane [8]
- An alternative reagent to bromine in Hofmann rearrangement[9]
- Dehydrogenation of hydrazones and hydrazines, for example that of hexafluoroacetone hydrazone to bis(trifluoromethyl)diazomethane[10][11]
- Cleavage of α-hydroxy acids[12] or 1,2-diols to their corresponding aldehydes or ketones, often replacing ozonolysis; for instance, the oxidation of di-n-butyl d-tartrate to n-butyl glyoxylate.[13]
- Reaction with alkenes to form γ-lactones
- Oxidation of alcohols carrying a δ-proton to cyclic ethers.[14]
- Oxidative cleavage of certain allyl alcohols in conjunction with ozone:[15][16]
- Transformation of 1,2-dicarboxylic acids or cyclic anhydrides to alkenes
- Conversion of acetophenones to phenyl acetic acids[17]
- Decarboxylation of carboxylic acids to alkyl halides in the Kochi reaction[18]
Safety
Lead(IV) acetate is toxic, because of lead. It is a neurotoxin. It badly affects the gum tissue, central nervous system, kidneys, blood, and reproductive system.