An electrophile is a widely used term in organic chemistry and it is an acceptor of the electron pair. They are positively charged having the vacant orbitals that are attracted towards the electron-rich center. Electrophile participates in the chemical reactions by accepting an electron pair for bonding to the nucleophile. Due to their properties of accepting electrons, they are also known as the Lewis acids. Most of the electrophiles are charged positively having an atom that mainly carries the partial positive charge or they have an atom that does not have the octet of the electrons.
Cations (NO+, H+), polarizable neutral molecules (Br2, Cl2), polarized neutral molecules (alkyl halide, acyl halides, HCl), some Lewis acids (DIBAL, BH3) and the oxidizing agents, and some chemical species not satisfying the octet rule such as radicals and carbenes are considered as electrophiles. Examples of the electrophiles are boron trifluoride, hydronium ion, halogen molecules, and aluminum chloride. Relevant electrophiles are generated biologically, during highly controlled metabolic processes or during the dysregulated pathological processes as byproducts of the oxidation process. Electrophiles modulate the survival of the cell at the various levels by chemically reacting with the nucleophilic nucleic acids, proteins, residues of amino acids and with other small molecules. Electrophiles confer the multiple signaling capabilities; however, it strongly depends on the structure and reactivity of the electrophiles.
Electrophiles are greedy atoms or little molecules. They are known for their specialty to do anything for two electrons (electron pair). They will happily take and grab the electron pairs from their neighboring atoms or molecules. They are electron deficient and they carry the full or partial positive charge and are eagerly looking for electron pair to make the covalent bond. They take the electron pair form the organic molecules and the sites of the organic molecules from which they take the electron are called electron rich. One can also consider them as electron loving.
They seem to behave like partially empty but they appear to attract the electrons as well. These partially empty substances look for the electron-rich center and are filled. They can be observed as photosensitive or electron sensitive. They are attacked by the most populated electron part of the nucleophiles and quite often they are used in the organic synthesis. Carbon dioxide is an electrophile.
Actually, the electrophilic atom is the carbon atom bonded to the electronegative atom, usually, halogen, nitrogen, Sulphur, or oxygen. The concept of electrophiles is quite simple. Generally, an atom that is poor in terms of electrons is an attractive target for anything that is electron rich. Let consider a hypothetical reaction in which methyl carbon is electrophile and in another one tertiary carbon is electrophile. Substituents on the electrophile (methyl carbon) have tiny hydrogens so it has a clear path for the backside attack. However, the backside attack on the tertiary carbon is not possible due to the bulky methyl groups. Carbocations are potent electrophiles and they are being extensively studied in the organic chemistry.