Arrange the following compounds in decreasing order of their reactivity towards 1,3-cyclopentadiene in a Diels-Alder reaction: (I) (II) (III)

Step-by-step solution

In a normal electron-demand Diels-Alder reaction, an electron-rich diene (like 1,3-cyclopentadiene) reacts with an electron-deficient dienophile. The reactivity of the dienophile increases with the presence of electron-withdrawing groups (EWGs) conjugated with the carbon-carbon double bond, as they lower the LUMO energy of the dienophile. Compound (III) is maleic anhydride, which has two strong electron-withdrawing carbonyl groups attached to the double bond, making it highly electron-deficient and the most reactiv