Nucleofiel

Nucleofiel, or nucleophile in English, is a chemical species that donates an electron pair to an electrophilic center, typically a carbon atom in a substrate. Nucleofielen are central to many organic reactions, including nucleophilic substitution (SN) and nucleophilic addition, and they can be either anions or neutral molecules with lone pairs or π electrons.

Nucleofielen come in various forms. They are often negatively charged (for example hydroxide, alkoxide, cyanide, thiolate, or amide ions), but neutral nucleophiles such as amines, phosphines, and water or alcohols can also act as nucleophiles. Ambident nucleophiles can attack through different atoms, as cyanide can donate from carbon or nitrogen, and thiolate or enolate species can attack via sulfur or oxygen.

Key properties and trends. Nucleophilicity depends on electron density and the ability to form a bond with the electrophile. It is influenced by charge, polarizability, and solvent effects. In protic solvents, larger, more polarizable anions often nucleophilate better than small, strongly basic ones, while in polar aprotic solvents nucleophilicity closely tracks basicity. The hard/soft character of a nucleophile interacts with the electrophile according to HSAB concepts. Nucleophilicity is not identical to basicity.

Typical reactions. Nucleofielen participate in SN2 and SNAr processes, conjugate (Michael) additions to α,β-unsaturated systems, and nucleophilic additions to carbonyl groups (as in Grignard or organolithium chemistry). They are essential for forming C–X and C–C bonds in organic synthesis.

In summary, a nucleofiel is any species capable of donating an electron pair to an electrophile, with behavior governed by charge, solvation, and structural factors.