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It is typically prepared by treating of red lead with acetic acid and acetic anhydride (Ac 2 O), which absorbs water. The net reaction is shown: [4] [5] Pb 3 O 4 + 4 Ac 2 O → Pb(OAc) 4 + 2 Pb(OAc) 2. The remaining lead(II) acetate can be partially oxidized to the tetraacetate by Cl 2, with a PbCl 2 by-product: 2 Pb(OAc) 2 + Cl 2 → Pb(OAc) 4 ...
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 ...
Alcohol oxidation is a collection of oxidation reactions in organic chemistry that convert alcohols to aldehydes, ketones, carboxylic acids, and esters. The reaction mainly applies to primary and secondary alcohols. Secondary alcohols form ketones, while primary alcohols form aldehydes or carboxylic acids. [1] A variety of oxidants can be used.
The reaction mechanism has similarities with the Baeyer-Villiger oxidation where the intermediate hydroxyperacid is called a Criegee intermediate. The per-acid forms a per-ester with the alcohol group. One alkyl substituent migrates from carbon to the adjacent oxygen atom, replacing the carboxylic acid leaving behind a carbocation.
Reaction of a lead(II) source with sodium cyclopentadienide gives the lead metallocene, plumbocene. Certain arene compounds react directly with lead tetraacetate to aryl lead compounds in an electrophilic aromatic substitution. For instance anisole with lead tetraacetate forms p-methoxyphenyllead triacetate: [4]
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 ...
The unusual alkyl nitrite starting material of the Barton reaction is prepared by attack of an alcohol on a nitrosylium cation generated in situ by dehydration of doubly protonated nitrous acid. [6] This series of steps is mechanistically identical to the first half of the mechanism formation of the more well-known aryl and alkyl diazonium salts.
Although the presence of an allylic alcohol does lead to increased stereoselectivity, the rates of these reactions are slower than systems lacking alcohols. However, the reaction rates of substrates with a hydrogen bonding group are still faster than the equivalent protected substrates. This observation is attributed to a balance of two factors.