Curly arrows can be used to explain the interaction between the structure of reactants and products, and their reactivity in the vast majority of organic reactions, regardless of their complexity. When used correctly they can even be used to predict possible outcomes of unknown processes and hence to design new synthetic reactions. They are a powerful tool for understanding and developing organic chemistry and it is vital that you become proficient in their use. They are the dynamic language of organic reaction mechanisms and they will appear in every chapter of the book from now on. Another equally important reason for mastering curly arrows now, as we start the system atic study of different types of reactions, is that the seemingly vast number of ‘different reactions’ turn out not to be so vast after all. Most organic reactions involve the movement of pairs of electrons between nucleophiles and electrophiles. And with relatively few types of organic nucleophiles and electrophiles involved in all these reactions, the similarity between seemingly unrelated reactions will become immediately apparent if you understand and can draw mechanisms. Learning to draw mechanisms means you can understand groups of related reactions rather than having to learn them individually. Drawing curly arrow mechanisms is a bit like riding a bike. Before you’ve mastered the skill, you keep falling off. Once you’ve mastered the skill, it seems so straightforward that you won der how you ever did without it. You’ll come across busy streets and complex traffic junctions, but with care you’ll get through safely.