Illustrated Glossary of Organic Chemistry

Curved arrows: Nonlinear arrows with barbs on one end used to indicate electron flow. A double-barbed arrow indicates motion of an electron pair, whereas a single-barbed arrow indicates motion of a single electron.

In this example, the curved arrows are shown in red. On the left side of the equilibrium, a lone pair on HO- oxygen shifts so as to become an O-H bond in water. The electron pair of the O-H bond in CH3COOH becomes a lone pair on oxygen in CH3CO2-. Note the equilibrium arrows (shown in blue) is not a curved arrows.