laya hair from leprosy calm and in this video i'll take you through the friedel-crafts isolation reaction and mechanism in the friedel-crafts isolation reaction we have benzene reacting with an acyl group or an acid chloride in the presence of a catalyst such as the alcl3 lewis acid to form an acyl group on the benzene ring this is very similar to the friedel-crafts alkylation reaction except for the carbonyl on the product but since the two are related I definitely recommend going back to the alkylation reaction first to make sure you understand the similarities and differences between the reactions you can find my complete series on electrophilic aromatic substitution by visiting my website layer for sicom slash EAS in the EAS intro video we talked about the super electrophile so let's see how we form it for this reaction the molecule that adds to the benzene is an acyl group and in this case we have an acid chloride this is a carboxylic acid derivative where we replace the O H from carboxyl with a chlorine the activation of the super electrophile is very similar to the activation you see in aromatic halogenation and friedel-crafts alkylation we have the acyl chlorine as the chlorine that doesn't know when to give up and aluminum which is an exception to the octet rule in that it can have just six valence electrons and three bonds and still be considered as a complete octet chlorine doesn't respect that exception and attacks the aluminum forming a bond between itself and aluminum this results in an aluminum atom with a total of four bonds and eight electrons and a formal charge of negative one and a chlorine atom with two bonds and four electrons for a formal charge of positive one chlorine as a halogen is highly electronegative and dislikes that positive charge and so to compensate it will grab the electrons from the carbonyl carbon break the bond and take the electrons for itself the resulting ALCL 4 still has a negative charge on the aluminum but chlorine is now neutral we'll leave this on the side but now let's see what happened to the acyl group the acyl group and we'll show the carbon atom here looks like it should be stable because we have a carbon double bound to an oxygen the problem is when chlorine broke away we didn't replace anything on the carbon atom and so carbon has an incomplete octet and a positive charge now while you have seen stable carbo cations in the past keep in mind that the carbo cation that starts out as an sp3 carbon with four bonds and then loses a pair of electrons for an incomplete octet while not stable is still stable enough in this case we started out with an sp2 hybridized carbon and then added the positive charge making it very very unstable Carbon really does not like having a PI bond and the carbo cation on the same atom and so it will pull on the electrons from oxygen giving us a resonance structure where carbon is now triple bound to oxygen the resulting resonance structure has a stable carbon with four bonds but an oxygen atom with three bonds one lone pair and a positive charge this structure is called the a cilium ion and this is the more stable of the two resonance because even though oxygen does not like that positive charge in a choice between a complete octet positive oxygen or incomplete octet double bound positive carbon the oxygen is more stable now that we have our super electrophile let's see how we add it to the benzene ring while the eighth ilium ion has a positive oxygen the charge is not completely on the oxygen remember that with resonance there is a constant back and forth and so the electrons between carbon and oxygen are drawn towards the oxygen atom making carbon very partially positive so even though oxygen is the positive Adam when benzene reaches out to attack its the carbon atom and not the oxygen that gets attacked the electrons that were being drawn towards oxygen are now able to completely break away from carbon and rest as a lone pair on the oxygen atom the resulting intermediate has a neutral carbon double bound to oxygen and single bound to an R group we also have a hydrogen on that same benzylic carbon atom making it sp3 hybridised and incapable of resonance and finally we have a positive charge on the other carbon on benzene where the PI bond broke away from to reform the aromaticity we bring back the ALCL form - specifically the chlorine that didn't know when to give up the chlorine will break away from aluminum and use those electrons to form a bond between itself and hydrogen but it only reaches for the hydrogen nucleus leaving the electrons to collapse away from hydrogen and towards that positive carbon on benzene these electrons are what reformed the benzene aromaticity giving us our final product and acyl group on benzene we also form a molecule of HCl and the alcl3 catalyst is regenerated and ready to proceed with another reaction friedel-crafts alkylation and isolation have important differences and similarities and so be sure to join me in the next video where I show you what you have to understand as similarities and differences between the two reactions you can catch my entire series on electrophilic aromatic substitution by visiting my website Laver sicom /e AAS are you struggling with organic chemistry are you looking for resources and information to guide you through the course and help you succeed if so and I have a deal for you a free copy of my ebook 10 secrets to acing organic chemistry use the link below or visit or go secrets.com to grab your free copy after downloading your FREE copy of my ebook you'll begin receiving my exclusive email updates with cheat sheets reaction guides study tips and so much more you'll also be the first to know when I have a new video or live review coming up if you enjoyed this video please click the thumbs up and share it with your organic chemistry friends and classmates I will be uploading many videos over the course of the semester so if you haven't subscribed to my channel yet do so right now to be sure that you don't miss out