Big Chemical Encyclopedia

Chemical substances, components, reactions, process design ...

Articles Figures Tables About

Alkenes polarizable nucleophiles

How does bromine attack the electron-rich double bond even though it does not appear to contain an electrophilic center The answer lies in the polarizability of the Br-Br bond, which is prone to heterolytic cleavage upon reaction with a nucleophile. The ir-electron cloud of the alkene is nucleophilic and attacks one end of the bromine molecule, with simultaneous displacement of the second bromine atom as bromide ion in an SN2-like process. [Pg.496]

The rr bond of an alkene results from overlapping of p orbitals and provides regions of increased electron density above and below the plane of the molecule. These electrons are less tightly bound than those in the a bonds, so are more polarizable and can interact with a positively charged electrophilic reagent. This forms the first part of an electrophilic addition, in which the electrons are used to form a a bond with the electrophile and leave the other carbon of the double bond electron deficient, i.e. it becomes a carbocation. This carbocation is then rapidly captured by a nucleophile, which donates its... [Pg.283]

The reaction is possible because the bond joining the two halogen atoms is relatively weak and therefore is easily broken (Table 5.1) and because Br2 and CI2 are polarizable. As the nucleophilic alkene approaches Br2 (or CI2), it induces a dipole, which causes one of the halogen atoms to have a partial positive charge. This is the electrophile that adds to the sp carbon of the alkene. The mechanism of the reaction is shown on page 257. [Pg.256]


See other pages where Alkenes polarizable nucleophiles is mentioned: [Pg.484]    [Pg.473]    [Pg.389]    [Pg.331]    [Pg.376]    [Pg.3283]    [Pg.499]    [Pg.3282]    [Pg.331]    [Pg.307]    [Pg.283]    [Pg.488]    [Pg.1287]   


SEARCH



Nucleophiles alkenes

© 2024 chempedia.info