Writing reaction mechanisms: the use of site-specific curly arrows as an aid to comprehension

Depicting the mechanism, the step-by-step path followed by a reaction, has evolved to also indicate the movement of electrons during each step through the use of curly arrows. The use of conventional curly arrows, as introduced by Robinson in the 1920s, can be ambiguous with regard to regiochemistry. Site-specific curly arrows, a refinement attributed to Woodward, remove this ambiguity. More importantly, our students indicate that they gain greater understanding and a clearer picture of the concepts under discussion through the use of site-specific arrows.