Electron deficiency

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In chemistry, electron deficiency (and electron-deficient) is jargon that is used in two contexts: chemical species that violate the

charge-transfer salts
.

Octet rule violations

Triphenylborane is classified as electron deficient.
Main article: Boranes

Traditionally, "electron-deficiency" is used as a general descriptor for boron hydrides and other molecules which do not have enough valence electrons to form localized (2-centre 2-electron) bonds joining all atoms.[1] For example, diborane (B2H6) would require a minimum of 7 localized bonds with 14 electrons to join all 8 atoms, but there are only 12 valence electrons.[2] A similar situation exists in trimethylaluminium. The electron deficiency in such compounds is similar to metallic bonding.

Electron-acceptor molecules

Structure of the charge-transfer complex between pyrene with the electron-deficient 1,3,5-trinitrobenzene.[3]

Alternatively, electron-deficiency describes molecules or ions that function as electron acceptors. Such electron-deficient species obey the octet rule, but they have (usually mild) oxidizing properties.

linear free-energy relationships: "a strongly negative ρ value indicates a large electron demand at the reaction center, from which it may be concluded that a highly electron-deficient center, perhaps an incipient carbocation, is involved."[6]

References

  1. ISBN 0130-39913-2
    . An electron-deficient species possesses fewer valence electrons than are required for a localized bonding scheme.
  2. doi:10.1039/qr9571100121
    . Retrieved 15 July 2020.
  3. S2CID 208752583
    .
  4. doi:10.1021/cm402219v
    .
  5. doi:10.1039/C3TC32062F
    .
  6. ISBN 978-0-471-72091-1
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