Diels-Alder: butadiene + ethylene
0 arrows drawnButadiene and ethylene combine in one concerted pericyclic step to give cyclohexene. Three pairs of pi electrons reorganize in a cycle; no intermediate, no charges, no leaving group.
Click an atom to start an arrow from a lone pair, or click a bond to start an arrow from that bond. Then click the atom or bond where the electrons land. Atoms are numbered by their position in the SMILES string. Keyboard: Tab to cycle focus, Enter to commit, Esc to cancel. Drag the small handle on a drawn arrow to sculpt the curve; double-click to reset.
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Two-electron is the default for ionic mechanisms. Switch to fishhook for radical / homolytic steps.
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