Explainer: why are curly arrows used in organic chemistry?

It’s been 100 years since curly, also known as curved, arrows first showed up in the scientific literature. Since then, they have made friends and foes, and gone from a novelty to an organic chemistry staple. While for the longest time, arrows were no more than a shorthand with no grounding in reality, evidence has started to emerge that the electron movement the arrows depict have an actual, real-life basis in quantum mechanics.

Today, seasoned chemists still push arrows around structures without much thought. The idea is that it allows creativity in rationalising mechanisms and reactions. But with textbooks still disagreeing on the best way to draw curly arrows, they remain one of the concepts chemistry students often struggle with.