Nucleofiilinen

Nucleofiilinen refers to the property of a chemical species to donate an electron pair to an electrophile, enabling the formation of a new chemical bond. In English, the term is nucleophilic and the species that display this behavior are called nucleophiles. Nucleophiles are typically electron-rich atoms or groups such as oxygen, nitrogen, sulfur, phosphorus, or carbon, and they are attracted to positively charged or polarized centers in other molecules.

Nucleophiles participate in a variety of reactions by attacking electrophilic centers. In substitution reactions, nucleophiles can displace leaving groups on saturated carbon atoms through mechanisms such as SN2, which involves a concerted back-side attack, or SN1, which proceeds via a carbocation intermediate followed by nucleophilic capture. Nucleophiles also add to π-bonds and carbonyl groups, forming addition products in processes common to organic synthesis and biochemistry.

Several factors influence nucleophilicity. Charge and polarizability play important roles: negatively charged and more polarizable species tend to be stronger nucleophiles. Solvent effects are significant: in polar protic solvents, nucleophilicity often increases down a group (for example, I− is more nucleophilic than F−), while in polar aprotic solvents, nucleophilicity correlates more closely with basicity. The concept is also described in terms of hard and soft nucleophiles, where soft nucleophiles prefer soft electrophiles in accordance with HSAB theory.

Common nucleophiles include hydroxide, alkoxides, amines, cyanide, thiolates, halide ions, and organometallic carbanions. Nucleophilicity is a central consideration in organic synthesis, catalysis, and enzymatic processes, influencing reaction rates, selectivity, and mechanism.