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Poor or imprecise curly arrows in organic mechanisms
“Common errors included poor drawing of curly arrows and mistakes in the structure of the intermediate.”— 7405/2, June 2022, Q01.8
How to fix: Every curly arrow tail must start on a lone pair drawn on an atom, or on the centre of a bond. The arrowhead points to where the electron pair is going. Never start an arrow from an atom symbol alone. In mechanisms, draw structures slightly larger than normal so arrow positions are unambiguous. A curly arrow in any mechanism must always start either from the line representing a covalent bond or from a lone pair drawn on an atom.