Organic Chemistry/Introduction to reactions/Drawing reactions
There are various techniques you will run across for notation of organic reactions.
Curved arrows are used to show movement of electrons. They are not used to show where atoms, ions, or molecules move, just electrons. A curved arrow with two "hooks" on the end indicated movement of a pair of electrons. A curved arrow with one "hook" indicated movement of one electron.
Double-headed arrows are used to represent equivalence between resonance structures.
Two-way double half arrows are represent a reaction that can go forward or reverse. If one of the half arrows is longer than the other it means that the reaction pathway favors that direction with the longer arrow.