DOUBLE SIDED ARROW SERIES

Useful in discussions of radical chemistry mechanisms in particular.

The single-headed (or “single-barbed”) arrow depicts the movement of a single electron.

DOUBLE SIDED ARROW SERIES

Deserving of a series of posts in itself.Ħ. Hugely important for following how mechanisms work. They start at the tail and end up at the head. The point of the curved, double-headed arrow is to show the movement of an electron pair. The curved arrow formalism is such an important tool that entire books have been devoted to it (for instance, I highly recommend checking out “ Arrow Pushing in Organic Chemistry” by Daniel Levy). Alternatively in a test situation it’s a way of visually depicting the question, “How would you do this?”ĥ. This is often used to show a speculative or theoretical transformation, where conditions might have yet to be discovered. Although it’s a separate discussion, it’s important to note that the molecule *does not* shuffle back and forth between these forms, but instead the “true picture” of the molecule is a combination or hybrid of these structures.Ĥ. That is to say they differ in the arrangements of their electrons and nothing else. Not to be confused with the equilibrium arrow, this double-headed arrow shows two (or more) species that are resonance structures of each other. To further highlight the position of an equilibrium, you may also occasionally see one of the arrows being longer than the other, showing that the equilibrium favors the starting materials or products.ģ. This shows a reaction that is reversible, usually in the context where the reversibility is being highlighted (such as in a reaction mechanism). These represent individual steps that could often be shown with individual arrows of their own, but they are placed in series here over the arrow to save space.Ģ. You’ll often see a sequence of reactions placed over the arrow and numbered “1), 2), 3), etc. There isn’t any hard and fast rule about what is supposed to go above or below the arrow, although reagents tend to go above and solvents tend to go below. That’s a pretty eventful day in the life of an alkene. Now, “BH3, then NaOH/H2O2” might not exactly seem like your idea of “action”, but put yourself in the alkene’s position – it’s double bond is being ripped asunder in order to form new bonds to boron and hydrogen, and then with the addition of H2O2, the bond to boron is replaced with one to oxygen. The purpose of this arrow is to show action. The forward arrow, otherwise known as the “reaction arrow”. To my knowledge there are 8 different types of arrows you meet in organic chemistry.

Double sided arrow