Synthesis of lodosalicylamide - An Electrophilic Aromatic Substitution Introduction Benzene can undergo certain types of reactions known as electrophilic aromatic substitutions (EAS). As the name implies, some atom or small molecule substitutes onto the benzene ring in place of a hydrogen atom. In today's experiment, we will be using a derivative of benzene, salicylamide, and substituting an iodine atom onto the ring. In all EAS reactions, the ring is the nucleophile while the atom/molecule that is being substituted onto the ring must have electrophilic character. Groups already present on the ring can either activate or deactivate the ring. Another way to think about this is that activating groups can speed up the rate of reaction while deactivating groups slow down the reaction. Activating groups will donate electron density into the ring an will specifically activate it's ortho and para positions. This is why we classify them as ortho, par directors. Deactivating groups will withdraw electron density from the ring. This electron withdrawing effect deactivates the ortho para positions towards nucleophilic attack, which in turn directs the substitution to its meta position. This is why deactivating groups are meta directors. The only exception to this statement is the halogens. The halogens do deactivate th ring, but they also can donate an electron pair into the ring via resonance. Therefore, halogem will be ortho para directing but deactivate the ring. Your organic lecture textbook and your instructor will have discussed this in further detail in lecture. More resources regarding these types of reactions can be found under this week's resources on Brightspace. The overall reaction is shown below. The line going through the benzene ring connected to iodine is a type of shorthand that can be used when you're unsure of the exact location of th substituent on the ring. As far as the exact location of the substitution, you'll need to predict based on your knowledge of the types of activating/deactivating groups already substituted salicylamide. NH₂ S OH 1.) Nal, NaOCI, CH₂CH₂OH 2.) Na2S₂O3, HCI NH₂ OH As a quick reference, the mechanism for the electrophilic aromatic substitution is shown bell The electrophile, It, is generated from 12. The nucleophile, the pi electrons of the ring, attack and loses aromaticity, forming a sigma complex. This sigma complex is a resonance stabilize carbocation intermediate. The ring will then regain aromaticity once it is deprotonated by a base.