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The Criegee oxidation is a glycol cleavage reaction in which vicinal diols are oxidized to form ketones and aldehydes using lead tetraacetate. It is analogous to the use of periodate (Malaprade reaction) but uses a milder oxidant. This oxidation was discovered by Rudolf Criegee and coworkers and first reported in 1931 using ethylene glycol as ...
Lead(IV) acetate or lead tetraacetate is an metalorganic compound with chemical formula Pb(C 2 H 3 O 2) 4. 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]
Another reagent is lead tetraacetate (Pb(OAc) 4). [4] These I- and Pb-based methods are called the Malaprade reaction and Criegee oxidation, respectively. The former is favored for aqueous solutions, the latter for nonaqueous solutions. [1] Cyclic intermediate are invariably invoked. The ring then fragments, with cleavage of the carbon–carbon ...
This makes carbon-14 an ideal dating method to date the age of bones or the remains of an organism. The carbon-14 dating limit lies around 58,000 to 62,000 years. [34] The rate of creation of carbon-14 appears to be roughly constant, as cross-checks of carbon-14 dating with other dating methods show it gives consistent results.
The source of platinum and palladium deposits is ultramafic rocks which have enough sulfur to form a sulfide mineral while the magma is still liquid. This sulfide mineral (usually pentlandite , pyrite , chalcopyrite , or pyrrhotite ) gains platinum by mixing with the bulk of the magma because platinum is chalcophile and is concentrated in sulfides.
Any excess lead-206, -207, and -208 is thus assumed to be radiogenic in origin, [12] allowing various uranium and thorium dating schemes to be used to estimate the age of rocks (time since their formation) based on the relative abundance of lead-204 to other isotopes. 207 Pb is the end of the actinium series from 235 U.
Commonly MVT deposits form by the combination of hydrocarbon pyrolysis liberating zinc-lead ions and sulfur to form an acidic solution which dissolves the host carbonate formation and replaces it with massive sulfide accumulations. This may also take the morphology of fault-hosted stockworks, massive tabular replacements and so forth.
In crustal rocks, it is present as the lead sulfide mineral galena. [1] Natural sources of lead in the lead cycle include wind borne dust, volcanic outgassing, and forest fires. [2] Natural weathering of rocks by physical and chemical agents can mobilize lead in soils. Mobilized lead can react to form oxides or carbonates.