nukleofilami

Nukleofilami, or nucleophiles, are chemical species that donate an electron pair to an electrophilic center to form a chemical bond. They are typically electron-rich atoms or ions that seek positively charged or polarizable centers. Nucleophiles can be charged (for example hydroxide, alkoxides, cyanide, azide, halide ions) or neutral (amines, alcohols, water, enolates, and many organophosphorus or organosulfur compounds). They are the counterpoint to electrophiles, which accept electron pairs.

Reactivity of nucleophiles depends on charge, basicity, and polarizability. Strong, small, negatively charged nucleophiles (such as hydroxide or alkoxides) often participate in bimolecular substitution or addition reactions, while highly polarizable species (such as iodide or thiolates) can be very effective in certain solvents. Solvent effects are important: protic solvents solvate anions via hydrogen bonding and can reduce nucleophilicity, whereas polar aprotic solvents increase nucleophilicity by not strongly solvating the nucleophile, often accelerating SN2 reactions.

Common contexts include nucleophilic substitution (S_N1 and S_N2) and nucleophilic additions to carbonyl compounds. In S_N2, the nucleophile attacks the electrophilic carbon in a concerted step, displacing a leaving group. In carbonyl chemistry, nucleophiles add to aldehydes and ketones to form alcohols after workup. Nucleophiles are central to many synthetic, biological, and industrial processes.

Hard–soft acid–base theory provides a framework: hard nucleophiles prefer hard electrophiles, while soft nucleophiles favor soft electrophiles, influencing selectivity and mechanism.