Chemistry Reference
In-Depth Information
isopropylidene triphenylphosphorane, illustrated below. Note that the phosphorus
possesses a positive charge and is electrophilic while the negative charge resides
on a carbon atom, rendering it nucleophilic.
The Wittig reaction mechanism involves addition of the anionic carbon atom to the
carbon atom of an aldehyde. As illustrated below, the now negatively charged
oxygen atom adds to the positively charged phosphorus atom, forming a four-
membered ring. This ring, known as a betaine, then decomposes to form an
olefin and triphenylphosphine oxide.
This is an example of a Diels-Alder reaction. This is an electrocyclic reaction
where no charges are involved. While no charges are involved, electron pairs do
move and their movement can be illustrated using arrow pushing. The mechanism,
illustrated below, involves aligning cyclopentadiene (a diene) with methyl vinyl
ketone (a dienophile) such that all three double bonds define a six-membered
