Visualize organic reaction mechanisms with animated electron arrow-pushing.
Nucleophilic addition to carbonyl compounds is one of the most important reaction classes in organic chemistry, forming the mechanistic basis for a huge share of synthetic transformations tested on AP Chemistry, Orgo 1/2, and IChO exams. This mechanism viewer focuses on that addition chemistry alongside the substitution and elimination fundamentals.
The carbonyl carbon (C=O) is electrophilic because oxygen's electronegativity pulls electron density away from carbon, leaving it partially positive and susceptible to nucleophilic attack. When a nucleophile attacks, the pi bond electrons move onto oxygen, generating a tetrahedral alkoxide intermediate — the single most common curved-arrow step in organic mechanisms. What happens next depends on the nucleophile and conditions: with water or alcohols under acid catalysis, this leads to hemiacetal and eventually acetal formation; with cyanide, it forms a cyanohydrin; with organometallic nucleophiles like Grignard reagents, it forms new carbon-carbon bonds en route to alcohols.
Acid catalysis accelerates carbonyl addition by protonating the carbonyl oxygen first, making the carbon even more electrophilic and allowing weaker nucleophiles to attack effectively — this is why acetal formation requires acid rather than proceeding readily under neutral conditions. Base catalysis works differently, typically generating a stronger, more reactive nucleophile (such as deprotonating an alcohol to an alkoxide) before it attacks the carbonyl.
This viewer also covers the SN1/SN2/E1/E2 substitution and elimination framework and electrophilic aromatic substitution, giving arrow-by-arrow animation for each — but its distinguishing strength is walking through carbonyl addition step by step: pi-bond attack, tetrahedral intermediate formation, and the acid- or base-catalyzed pathway that determines the final product. Click through each animated step to see exactly where electrons move and why the reaction proceeds the way it does — essential preparation for any exam that asks you to draw a full mechanism, not just predict a product.