Nucleophiladditionen

Nucleophilic addition is a fundamental type of organic reaction where a nucleophile, an electron-rich species, attacks an electron-deficient atom, typically a carbon atom in a carbonyl group. This attack leads to the formation of a new covalent bond between the nucleophile and the carbon atom, while the pi bond of the carbonyl group breaks, often forming an alkoxide intermediate. The subsequent protonation of this intermediate regenerates the carbonyl oxygen and yields the addition product.

Common nucleophiles include Grignard reagents, organolithium compounds, cyanide ions, and hydrides. Electrophiles that undergo nucleophilic addition are typically compounds with polar double or triple bonds, most notably carbonyl compounds like aldehydes and ketones, as well as esters, amides, and nitriles. The reaction mechanism generally proceeds in two steps. First, the nucleophile attacks the electrophilic center, pushing electrons from the pi bond onto the more electronegative atom (usually oxygen). Second, a proton or other electrophile is transferred to the negatively charged atom.

Nucleophilic addition reactions are crucial for the synthesis of a wide range of organic molecules, including alcohols, carboxylic acids, and amines. Examples include the Grignard reaction, which adds alkyl or aryl groups to carbonyls, and the Wittig reaction, which forms alkenes from aldehydes or ketones. The reactivity of the carbonyl compound is influenced by steric and electronic factors; electron-withdrawing groups and less steric hindrance generally enhance reactivity.