nukleofiliaa

Nukleofiliaa refers to the relative tendency of a species to donate an electron pair to an electrophilic center, enabling bond formation in chemical reactions. It is a key concept in organic and inorganic chemistry, influencing rates of SN2 substitutions, nucleophilic additions to carbonyls, and metallation processes. A nucleophile can be an anion (for example HO-, CN-, CH3O-), a neutral molecule with a lone pair (NH3, H2O), or a pi-system that can supply electron density.

Several factors determine nukleofiliaa: electron density and charge (more electron-rich or negatively charged nucleophiles are often more nucleophilic), polarizability (softer nucleophiles prefer softer electrophiles), and steric hindrance (bulkier nucleophiles are less effective). Solvent has a major effect: in polar protic solvents, smaller, highly charged nucleophiles are heavily solvated, making nucleophilicity trends follow electronegativity down the group (I- > Br- > Cl- > F-). In polar aprotic solvents, nucleophilicity more closely tracks basicity, so F- can be among the strongest nucleophiles.

Nukleofiliaa is not identical to basicity; basicity measures proton affinity, whereas nucleophilicity measures attack on a typical electrophile. The two can diverge, depending on solvent and reaction type. In SN2 reactions, nucleophilicity directly affects rate: faster nucleophiles give higher rates, all else equal.

Measurement and ranking are typically expressed in relative terms or via rate constants, often using standard reference nucleophiles. Understanding nukleofiliaa helps predict reaction outcomes, selectivity, and mechanism in synthesis.