Electron-rich is jargon that is used in multiple related meanings with either or both kinetic and thermodynamic implications:
* with regards to
electron-transfer, electron-rich species have low
ionization energy
In physics and chemistry, ionization energy (IE) is the minimum energy required to remove the most loosely bound electron of an isolated gaseous atom, Ion, positive ion, or molecule. The first ionization energy is quantitatively expressed as
: ...
and/or are
reducing agent
In chemistry, a reducing agent (also known as a reductant, reducer, or electron donor) is a chemical species that "donates" an electron to an (called the , , , or ).
Examples of substances that are common reducing agents include hydrogen, carbon ...
s.
Tetrakis(dimethylamino)ethylene is an electron-rich alkene because, unlike
ethylene
Ethylene (IUPAC name: ethene) is a hydrocarbon which has the formula or . It is a colourless, flammable gas with a faint "sweet and musky" odour when pure. It is the simplest alkene (a hydrocarbon with carbon–carbon bond, carbon–carbon doub ...
, it forms isolable
radical cation. In contrast, electron-poor alkene
tetracyanoethylene is an electron acceptor, forming isolable anions.
* with regards to
acid-base reactions, electron-rich species have high
pKa's and react with weak
Lewis acid
A Lewis acid (named for the American physical chemist Gilbert N. Lewis) is a chemical species that contains an empty orbital which is capable of accepting an electron pair from a Lewis base to form a Lewis adduct. A Lewis base, then, is any ...
s.
* with regards to
nucleophilic substitution reactions, electron-rich species are relatively strong nucleophiles, as judged by rates of attack by electrophiles. For example, compared to
benzene
Benzene is an Organic compound, organic chemical compound with the Chemical formula#Molecular formula, molecular formula C6H6. The benzene molecule is composed of six carbon atoms joined in a planar hexagonal Ring (chemistry), ring with one hyd ...
,
pyrrole is more rapidly attacked by electrophiles. Pyrrole is therefore considered to be an electron-rich aromatic ring. Similarly, benzene derivatives with electron-donating groups (EDGs) are attacked by electrophiles faster than in benzene. The electron-donating vs electron-withdrawing influence of various functional groups have been extensively parameterized in
linear free energy relationships.
* with regards to
Lewis acid
A Lewis acid (named for the American physical chemist Gilbert N. Lewis) is a chemical species that contains an empty orbital which is capable of accepting an electron pair from a Lewis base to form a Lewis adduct. A Lewis base, then, is any ...
ity, electron-rich species are strong
Lewis bases.
[{{cite journal , doi=10.1021/ar9501479, title=Recognition of Electron-Donating Guests by Carborane-Supported Multidentate Macrocyclic Lewis Acid Hosts: Mercuracarborand Chemistry , year=1997 , last1=Hawthorne , first1=M. Frederick , last2=Zheng , first2=Zhiping , journal=Accounts of Chemical Research , volume=30 , issue=7 , pages=267–276]
See also
*
Electron-withdrawing group
References
Physical organic chemistry">trinitrobenzene.html" ;"title="benzene, trinitrobenzene">benzene, trinitrobenzene forms adducts -->
Physical organic chemistry
Chemical bonding