Electron deficiency

In chemistry, electron deficiency (and electron-deficient) is jargon that is used in two contexts: chemical species that violate the octet rule because they have too few valence electrons and species that happen to follow the octet rule but have electron-acceptor properties, forming donor-acceptor charge-transfer salts.

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.

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.

[5] Electron deficiency can be measured by 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.