As we learned in chemistry class, chemical reaction occurs with the formation or cleavage of bonds between atoms. These chemical bonds form when atoms share or exchange electrons. The chemical reactivity can be controlled in several ways. Among them, the control of electronic property at the reaction site is generally employed. For example, electron-rich molecule prefers to react with a molecule that can readily accept electrons. Many atoms can form ‘functional groups’ that either donate or withdraw electrons and control the electron density distribution of a molecule. These functional groups can vary the electronic property of the molecule to speed up the intended chemical reaction. Commonly referred to as “inductive effect,” the electron-donating group pushes electrons to increase the electron density at the site where the reaction takes place. Conversely, electron-withdrawing group removes electrons and reduces the electron density of the reaction site.
In 1937, the American chemist Louis P.