Update: Step 2 of the Multistep Synthesis; The Diels-Alder Reaction

Hello all,

Like the Wittig Reaction, the Diels-Alder Reaction is used extensively in Organic Synthesis to generate carbon-carbon bonds. This particular reaction, first described in 1928 by Nobel laureates Otto Diels and Kurt Alder, involves the [4+2] cycloaddition of a cis conjugated diene, and a dienophile (which can be an alkene or alkyne). The reaction produces cyclohexenes and it is very easy to control the steriochemical properties of the formed product.

When the Diels- Alder reaction takes place, the molecules move to a system with less pi bonds, and more sigma bonds than the starting system. Sigma bonds are more energetically stable than pi bonds, so, as with the Wittig Reaction, one of the main forces driving the Diels-Alder reaction to completion is the stability gained by the formation of the product.

In addition, all of my students were able to successfully complete the first step of my reaction in lab yesterday. However, there seems to be an issue with re-crystallization that is leading to a lower yield then what I had experienced. I believe increasing the time spent for re-crystallization will allow a higher yield, also it may be necessary to increase the amounts of starting reagents for the first step.

Comments

  1. semodlin says:

    Hello Tim, I have two questions in regards to the yield. How long do you believe you should increase the time spent for re-crystallization? And how much more of the starting reagents should be increased? I liked my yield from yesterday

  2. Tim Beck says:

    Hello Sarah,
    I am going to increase the re-crystallization time from 10 to 20 minutes and use an additional 20% reagent amounts. The biggest issue was the majority of the class could not come up with the full amount required for step 3, however this should be fixed in time for the Fall 2016 labs.