In chemistry, electrophilicity (from the Greek philos "friend") is an abstract measure of the ability of an electrophilic (electron-loving) molecule to react with another molecule that has an increased electron density . The electron-poor particle is called the electrophile , the reaction partner is called the nucleophile . Electrophilic particles are positively charged or have a strong positive partial charge . As a result of the reaction, the formation of a covalent bond can be observed due to the charge difference between the two particles .
Electrophilic particles or atoms are positively charged ( cations ), positively polarized ( dipoles ) or generally tend to take up electrons . They are therefore attracted to negative charges . Typical electrophiles are carbocations , protons (H + ) and halogens, as well as carbonyl compounds and Lewis acids .
Electrophiles preferably enter into addition reactions ( electrophilic addition , A E ) on a double bond with two carbon atoms or substitution reactions ( electrophilic aromatic substitution , S E ) on an aromatic ring .
The opposite of electrophilic is electrophobic (Greek phobos = fear). Such a molecule or ion repels electrons because it has a lone pair of electrons . Electrophobia is mostly called nucleophilicity .
|Electrophilicity index some selected values (dimensionless)|
The electrophilicity index also applies to free radicals . Strongly electrophilic residues such as those of the halogens react with electron-rich reaction sites and strongly nucleophilic residues such as the 2-hydroxypropyl-2-yl and tert- butyl residues, which themselves react with a preference for electron-deficient reaction sites.
- Electrophilicity Index Parr, RG; Szentpaly, L. v .; Liu, SJ Am. Chem. Soc .; 1999; 121 (9); 1922–1924, doi : 10.1021 / ja983494x .
- Electrophilicity Index Chattaraj, PK; Sarkar, U .; Roy, DR Chem. Rev .; 2006 ; 106 (6); 2065-2091, doi : 10.1021 / cr040109f .
- Electrophilicity Index Parr, RG; Szentpaly, L. v .; Liu, S. J. Am. Chem. Soc. ; 1999 ; 121 (9); 1922–1924, doi : 10.1021 / ja983494x .
- Electrophilicity and Nucleophilicity Index for Radicals Freija De Vleeschouwer, Veronique Van Speybroeck, Michel Waroquier, Paul Geerlings, and Frank De Proft Org. Lett .; 2007; 9 (14) pp. 2721-2724, doi : 10.1021 / ol071038k .