Lead(IV) acetate explained

Lead(IV) acetate or lead tetraacetate is an metalorganic compound with chemical formula . 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.^[1]

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.^[2]

Preparation

It is typically prepared by treating of red lead with acetic acid and acetic anhydride, which absorbs water. The net reaction is shown:^{[3] [4]}

The remaining lead(II) acetate can be partially oxidized to the tetraacetate by Cl₂, with a PbCl₂ by-product:

Reagent in organic chemistry

Lead tetraacetate is a strong oxidizing agent,^[5] 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,^[6] and α-oxygen ether C−H bonds, for example the conversion of dioxane to 2-acetoxy-1,4-dioxane ^[7]
• An alternative reagent to bromine in Hofmann rearrangement^[8]
• Dehydrogenation of hydrazones and hydrazines, for example that of hexafluoroacetone hydrazone to bis(trifluoromethyl)diazomethane^{[9] [10]}
• Cleavage of α-hydroxy acids^[11] or 1,2-diols to their corresponding aldehydes or ketones, often replacing ozonolysis; for instance, the oxidation of di-n-butyl -tartrate to n-butyl glyoxylate.^[12]
• Reaction with alkenes to form γ-lactones
• Oxidation of alcohols carrying a δ-proton to cyclic ethers.^[13]
• Oxidative cleavage of certain allyl alcohols in conjunction with ozone:^{[14] [15]}
• Transformation of 1,2-dicarboxylic acids or cyclic anhydrides to alkenes

• Conversion of acetophenones to phenyl acetic acids^[16]
• Decarboxylation of carboxylic acids to alkyl halides in the Kochi reaction^[17]

Safety

Lead(IV) acetate is toxic. It is a neurotoxin. It affects the gum tissue, central nervous system, kidneys, blood, and reproductive system.

References

Notes and References

1. Encyclopedia: Mihailo Lj. Mihailović . Živorad Čeković . Brian M. Mathes . Encyclopedia of Reagents for Organic Synthesis. 2005. 10.1002/047084289X.rl006.pub2. 978-0-471-93623-7. Lead(IV) Acetate.
2. Schürmann . M. . Huber . F. . A redetermination of lead(IV) acetate . Acta Crystallographica Section C . 50 . 11 . 1994 . 1710–1713 . 0108-2701 . 10.1107/S0108270194006438.
3. Book: J. C. Bailar, Jr. . Inorganic Syntheses . Inorganic Syntheses . 1 . 47–49 . 1939 . Lead Tetracetate . 10.1002/9780470132326.ch17. 978-0-470-13232-6.
4. Book: M. Baudler. Lead(IV) Acetate. Handbook of Preparative Inorganic Chemistry, 2nd Ed. . G. Brauer. Academic Press. 1963. NY,NY. 2. 767.
5. J. Zýka . Analytical study of the basic properties of lead tetraacetate as oxidizing agent . Pure and Applied Chemistry . 1966 . 13 . 4 . 569–581 . 10.1351/pac196613040569 . 96821219 . 19 December 2013.
6. 10.15227/orgsyn.072.0057 . (1R,5R)-(+)-Verbenone of High Optical Purity . Organic Syntheses . 1995 . 72 . 57 .
7. [Organic Syntheses]
8. Baumgarten, Henry . Smith, Howard . Staklis, Andris . Reactions of amines. XVIII. Oxidative rearrangement of amides with lead tetraacetate. The Journal of Organic Chemistry. 1975. 40. 24. 3554–3561. 10.1021/jo00912a019.
9. 10.15227/orgsyn.050.0006 . Bis(Trifluoromethyl)Diazomethane . Organic Syntheses . 1970 . 50 . 6. W. J. . Middleton. D. M. . Gale .
10. 10.15227/orgsyn.055.0114 . Preparation of N-Aminoaziridines: trans-1-Amino-2,3-diphenylaziridine, 1-Amino-2-phenylaziridine, and 1-Amino-2-phenylaziridinium Acetate . Organic Syntheses . 1976 . 55 . 114. Robert K. Muller, Renato Joos, Dorothee Felix, Jakob Schreiber, Claude Wintner, and A. Eschenmoser .
11. Ōeda. Haruomi. Oxidation of some α-hydroxy-acids with lead tetraacetate. Bulletin of the Chemical Society of Japan. 1934. 9. 1. 8–14. 10.1246/bcsj.9.8. free.
12. Organic Syntheses, Coll. Vol. 4, p.124 (1963); Vol. 35, p.18 (1955) Article.
13. M B Smith, J March. March's Advanced Organic Chemistry (Wiley, 2001)
14. O₃/Pb(OAc)₄: a new and efficient system for the oxidative cleavage of allyl alcohols. E. J.. Álvarez Manzaneda. R.. Chahboun. M. J.. Cano. E.. Cabrera Torres. E.. Álvarez. R.. Álvarez Manzaneda. A.. Haidour. J. M.. Ramos López. Tetrahedron Letters. 47. 37. 2006. 6619–6622. 10.1016/j.tetlet.2006.07.020.
15. Conversion of 1-allylcyclohexanol to cyclohexanone, in the proposed reaction mechanism the allyl group is first converted to a trioxalane according to conventional ozonolysis which then interacts with the alkoxy lead group.
16. Synthesis. 1981. 2. 2. 126–127. One-Step Synthesis of Methyl Arylacetates from Acetophenones Using Lead(IV) Acetate. 10.1055/s-1981-29358. Myrboh. B.. Ila. H.. Junjappa. H..
17. A New Method for Halodecarboxylation of Acids Using Lead(IV) Acetate. Jay K. Kochi. J. Am. Chem. Soc.. 1965. 87. 11. 2500–02 . 10.1021/ja01089a041.