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The rule states that with the addition of a protic acid HX or other polar reagent to an asymmetric alkene, the acid hydrogen (H) or electropositive part gets attached to the carbon with more hydrogen substituents, and the halide (X) group or electronegative part gets attached to the carbon with more alkyl substituents. This is in contrast to ...
In hydroboration, alkenes insert into borane B-H bonds, with anti-Markovnikov stereochemistry. Hydroboration occurs stereospecifically syn — on the same alkene face. The transition state for this concerted reaction can be visualized as a square with the corners occupied by carbon, carbon, hydrogen and boron, maximizing overlap between the ...
In the case of metal-alkenes and alkynes, the strengthening of the M–C 2 R 4 and M–C 2 R 2 bond is reflected in bending of the C–C–R angles which assume greater sp 3 and sp 2 character, respectively. [8] [9] Thus strong π backbonding causes a metal-alkene complex to assume the character of a metallacyclopropane. [10]
The stronger the donation is, the stronger the back bonding from the metal d orbital to π* anti-bonding orbital of the alkene. This effect lowers the bond order of the alkene and increases the C-C bond length. One example is the complex PtCl 3 (C 2 H 4)] −. These complexes are related to the mechanisms of metal-catalyzed reactions of ...
K. Barry Sharpless was the first to develop a general, reliable enantioselective alkene dihydroxylation, referred to as the Sharpless asymmetric dihydroxylation (SAD). Low levels of OsO 4 are combined with a stoichiometric ferricyanide oxidant in the presence of chiral nitrogenous ligands to create an asymmetric environment around the oxidant.
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.
In acetylene, the H–C≡C bond angles are 180°. By virtue of this bond angle, alkynes are rod-like. Correspondingly, cyclic alkynes are rare. Benzyne cannot be isolated. . The C≡C bond distance of 118 picometers (for C 2 H 2) is much shorter than the C=C distance in alkenes (132 pm, for C 2 H 4) or the C–C bond in alkanes (153 p
Alkenes that are particularly amenable to asymmetric hydrogenation often feature a polar functional group adjacent to the site to be hydrogenated. In the absence of this functional group, catalysis often results in low ee's. For some unfunctionalized olefins, iridium with P,N-based ligands) have proven effective, however. Alkene substrates are ...