karbonüüllisamisel

Karbonüüllisamisel, also known as carbonyl addition, is a fundamental reaction in organic chemistry where a nucleophile attacks the electrophilic carbonyl carbon atom of a carbonyl compound. This reaction is characteristic of aldehydes and ketones, as well as carboxylic acid derivatives like esters, amides, and acid halides. The carbonyl group (C=O) is polar due to the electronegativity difference between carbon and oxygen, making the carbon atom partially positive and susceptible to attack by electron-rich species.

The general mechanism involves the nucleophile's electrons forming a new bond with the carbonyl carbon. This causes the pi bond of the carbonyl group to break, and the electrons move onto the oxygen atom, creating an alkoxide intermediate. This alkoxide is typically stabilized by the presence of a proton source in the reaction mixture, which protonates the oxygen to form an alcohol or related functional group.

Common nucleophiles in carbonyl addition reactions include Grignard reagents, organolithium compounds, hydride sources (like sodium borohydride or lithium aluminum hydride), cyanide ions, and alcohols. The specific outcome of the reaction depends on the nature of the carbonyl compound and the nucleophile. For instance, Grignard reagents add to aldehydes and ketones to form alcohols, while hydride reagents reduce them to alcohols as well. Carboxylic acid derivatives undergo nucleophilic acyl substitution, where the initial addition is followed by the elimination of a leaving group. Understanding carbonyl addition is crucial for synthesizing a wide range of organic molecules.