Triple Bonds

Congratulations! You have made it through stage one of your organic chemistry journey. You have learned the foundations of arrow pushing (nucleophilic attack, loss of leaving group, proton transfer, rearrangement, and resonance)and the basic reaction types (substitution, elimination, and addition). From here on out you will revisit each of these topics as you study additional functional groups.

Our first functional group is triple bonds. Let’s begin with thinking about triple bonds as a reagent, meaning how will it react? Remember, structure impacts reactivity. Look at the alkyne below. What does it look very similar to?

Yes – an alkene. The only difference is the additional pi bond. Previously, we saw how pi bonds are electron-rich and can be transformed to alkanes in the presence of a strong acid through addition reactions. The same is true for triple bonds (and yes you will still need to remember to make the more stable C+ intermediate for asymmetric alkynes!).

Now let’s try to think of ways to make an alkyne. Well how have we seen pi bonds formed previously?

Yes – through elimination reactions. Same is true for the pi bond of an alkyne.

Review the mechanisms for reactions of alkynes and formation of alkynes in the videos below. Then practice these mechanisms on your own using the recommended puzzles.