Search results
Results from the WOW.Com Content Network
An addition reaction is the reverse of an elimination reaction, in which one molecule divides into two or more molecules. For instance, the hydration of an alkene to an alcohol is reversed by dehydration .
The less hindered faces of the enone and alkene react. [9] Intramolecular enone–alkene cycloaddition may give either "bent" or "straight" products depending on the reaction regioselectivity. When the tether between the enone and alkene is two atoms long, bent products predominate due to the rapid formation of five-membered rings. [10]
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.
In organic chemistry, syn-and anti-addition are different ways in which substituent molecules can be added to an alkene (R 2 C=CR 2) or alkyne (RC≡CR).The concepts of syn and anti addition are used to characterize the different reactions of organic chemistry by reflecting the stereochemistry of the products in a reaction.
Carbocations are formed in two major alkene addition reactions. In an HX addition reaction, the pi bond of an alkene acts as a nucleophile and bonds with the proton of an HX molecule, where the X is a halogen atom. This forms a carbocation intermediate, and the X then bonds to the positive carbon that is available, as in the following two-step ...
Adding the hydrogen ion to one carbon atom in the alkene creates a positive charge on the other carbon, forming a carbocation intermediate. The more substituted the carbocation, the more stable it is, due to induction and hyperconjugation. The major product of the addition reaction will be the one formed from the more stable intermediate.
The Povarov reaction requires a Lewis acid such as boron trifluoride to activate the imine for an electrophilic addition of the activated alkene. This reaction step forms an oxonium ion which then reacts with the aromatic ring in a classical electrophilic aromatic substitution. Two additional elimination reactions create the quinoline ring ...
In organic chemistry, the ene reaction (also known as the Alder-ene reaction by its discoverer Kurt Alder in 1943) is a chemical reaction between an alkene with an allylic hydrogen (the ene) and a compound containing a multiple bond (the enophile), in order to form a new σ-bond with migration of the ene double bond and 1,5 hydrogen shift.