In chemistry, an electron-deficient compound or molecule is a chemical species that has a relative deficiency of electrons compared to the number of its valence electrons. This can occur when there are not enough valence electrons to form the usual number of covalent bonds, or when there is a high degree of positive charge on an atom.

Electron-deficient compounds are often found in coordination chemistry, where they act as Lewis acids by accepting electron pairs from other molecules or ions. This can lead to the formation of stable complexes, which are important in many biological processes such as oxygen transport and catalysis.

Some examples of electron-deficient compounds include:

* Boron trifluoride (BF3)

* Carbon monoxide (CO)

* Nitric oxide (NO)

* Sulfur dioxide (SO2)

These compounds are all able to accept electron pairs from other molecules or ions, forming stable complexes. For example, BF3 can react with ammonia (NH3) to form the complex BF3NH3.

Electron-deficient compounds can also be found in organic chemistry, where they are often referred to as carbocations. Carbocations are positively charged carbon atoms that are missing an electron. They are highly reactive and can undergo a variety of reactions, including addition, substitution, and elimination.

Some examples of carbocations include:

* The methyl cation (CH3+)

* The ethyl cation (C2H5+)

* The tert-butyl cation (C(CH3)3+)

These carbocations are all highly reactive and can undergo a variety of reactions. For example, the methyl cation can react with water to form methanol (CH3OH).

Electron-deficient compounds are important in a variety of chemical processes, and they play a vital role in many biological systems.