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The periselectivity of a particular reaction depends on the structure of both the ketene and the substrate. Although the reaction is predominantly used to form four-membered rings, a limited number of substrates undergo [3+2] or [4+2] reactions with ketenes. Examples of all three modes of cycloaddition are discussed in this section.
Although less active than more acidic peracids (e.g., m-CPBA), peracetic acid in various forms is used for the epoxidation of various alkenes (Prilezhaev reaction). Useful applications are for unsaturated fats, synthetic and natural rubbers, and some natural products such as pinene. A variety of factors affect the amount of free acid or ...
The most common use of organic peroxy acids is for the conversion of alkenes to epoxides, the Prilezhaev reaction. Formation of an epoxide from an alkene and a peroxycarboxylic acid. Another common reaction is conversion of cyclic ketones to the ring-expanded esters using peracids in a Baeyer-Villiger oxidation .
In organic chemistry, a rearrangement reaction is a broad class of organic reactions where the carbon skeleton of a molecule is rearranged to give a structural isomer of the original molecule. [1] Often a substituent moves from one atom to another atom in the same molecule, hence these reactions are usually intramolecular. In the example below ...
Original reactions reported by Baeyer and Villiger. There were three suggested reaction mechanisms of the Baeyer–Villiger oxidation that seemed to fit with observed reaction outcomes. [16] These three reaction mechanisms can really be split into two pathways of peroxyacid attack – on either the oxygen or the carbon of the carbonyl group. [17]
The metal-mediated processes include a carbonyl-olefination and an olefin–olefin metathesis event. There are two general mechanistic schemes to perform this overall transformation: one, reaction of a [M=CHR 1] reagent with an alkene to generate a new metal alkylidene, which then couples with a carbonyl group to form the desired substituted alkene and an inactive [M=O] species (type A); two ...
Substituted ketenes can be prepared from acyl chlorides by an elimination reaction in which HCl is lost: Formation of a ketene from an acyl chloride. In this reaction, a base, usually triethylamine, removes the acidic proton alpha to the carbonyl group, inducing the formation of the carbon-carbon double bond and the loss of a chloride ion:
The same is true when an alkene reacts with water in an additional reaction to form an alcohol that involves carbocation formation. The hydroxyl group (OH) bonds to the carbon that has the greater number of carbon-carbon bonds, while the hydrogen bonds to the carbon on the other end of the double bond, that has more carbon–hydrogen bonds.