CHEM 3410 Lecture Notes - Lecture 2: Cyclohexene, Stereospecificity, Stereochemistry
Document Summary
One of the most striking differences between conjugated and nonconjugated dienes is that the conjugated dienes react with alkenes to produce a cyclohexene. In the transition state of this reaction, the two alkene carbons and the carbons 1 and 4 of the diene rehybridizes from an from sp2 to sp3. The dienophile makes the reaction most rapid when there is an electron-withdrawing substituent group. This reaction is stereospecific, meaning whatever the stereochemistry of the dienophile, the product will also be the same stereochemistry. The reaction orients itself in a way that forms the endo product rather than the exo. The reactants are positioned directly above each other so that the electron withdrawing substituent on the dienophile is under the diene double bond. The diene must be able to adopt a s-cis conformation. This means that the diene has to be able to rotate between carbon 2 and 3.
