Electrophilic Aromatic Substitution Essay

The experiment focuses on finding erupt what kind of pioneer effects that quaternity different substituents will have on an aromatic benzene coterie. The substituents be tried argon aniline, anisole, ethanamide (acetanilide), and hydroxybenzene. only quartette of these groups are either para or ortho activating. Bromination is the defendion that will be carried out(p). The melt down point ranges of the final gos will be taken in evidence to go out their identities and reactivity. It is predicted that substitution order from most to least(prenominal) reactive should be aniline, carbolic acid, anisole, and ethanamide. TheoryRegioselectivity and the prise of electrophilic aromatic substitution are affected by the substituents attached to the original benzene. In electrophilic aromatic substitution, (EAS for short), the count determining timbre is the commencement step of the reaction. This experiment deals with activating substituents that increase the rate of re action. In the first rate determining step, the electron tightfistedness rich pi bonds of benzene react with the electrophile (Bromine) to form a plangency alter carbocation. This step is the most important doer that decides which substituents make benzene react fleet. This is because the rate of the reaction can be fixed through the stability of the carbocation alteration tell apart hybrid, which is in like manner known as rapport effect and the Hammond Postulate. In other words, if a carbocation intermediate is more permanent, there is little scarceton needed in the transition state to form the carbocation. Less energy needed translates to a faster reaction.All in on the whole, substituents that increase the electron compactness on the ring contribute by making the benzene ring more nucleophilic through increase electron niggardness. The increased electron tightness around the ring would help to stabilize the positively supercharged carbocation intermediate. Thi s federal agency that this intermediate is more apt(predicate) to form. Electron donating substituents would activate the ring towards EAS, which means the overall rate would be faster compared to benzene. The aniline group forms the most stable carbocation because it has the same resonance effects as the other groups but because nitrogen is slight damaging than oxygen, its inductive effects are weaker. Therefore aniline should react the fastest. ethanamide would be last in harm ofreactivity because it has the weakest resonance effects compared to inductive effects, in other words it is the weakest electron donating group. The order of reactivity from strongest activator to least should be aniline, phenol, anisole, and acetamide. It is also predicted that all of the groups should react towards a polyhalogenated carrefour except for acetamide. Specifically, they should all be tri-substituted except for acetamide. Steric hindrance also plays a factor in preventing Br from bein g added to the ortho positions, so it should be expected that the acetamide harvest-home should only have a substituent added to the para position.ResultsCompound/Group warming Point Range (C)Productacetamide (Johnson/Leo)164.2-168.84-bromoacetamideaniline (Iris/Jenelle)120-130.42,4,6-tribromoanilinephenol (Jack/Kyle)90-932,4,6-tribromophenolanisole (N/A)40-43 and 55.3-73.72,4-dibromoanisoleAnisole result did not recrystallize so data is taken from other labs.Crude mass product of acetamide 0.235gRecrystallized product mass of acetamide 0.087gTheoretical go 0.0625gPercent yield 139%DiscussionAniline and phenol twain formed a tri-substituted product in both ortho and one para positions tally to their respective resolve point ranges. Thisconfirms expectations that these two substituents are the strongest activators. This is because the NH2 and OH groups are very electronegative and reactive which allows their carbocation resonance structures to be stabilized. take down though both aniline and phenol had the same amount of polybromination, we know that since nitrogen is less(prenominal) electronegative than oxygen, aniline has less inductive effects. In turn, it means that aniline would have more electron density which make makes it more reactive to electrophiles. Although the anisole did not form a product, retrieved data suggests that the product is is actually disubstituted this contradicts the prediction that it would be trisubstituted also it is not surprising because anisole has an extra carbon attached to the oxygen which could weaken resonance effects.Lastly, the melting point ranges for the acetamide product suggest that it formed 4-bromoacetamide. Based on the data gathered, the ranking in order of increasing activity would be aniline, phenol, anisole, and acetamide. This matches up with initial predictions. These results make sense because anisole and acetamide have resonance structures where the electron density is moved outside of the ring so it cannot activate the benzene ring as well as the other two. With regards to the cogency of the reaction, three of the reactions appeared to be efficient. Aniline, phenol, and acetamide all reacted efficiently. This is observed through their products which displayed conclusive melting point ranges that confirmed their predictions. Although 10% bromine solution was used these reactions carried to completion and their yields were decent. shutdownAniline and Phenol both yield trisubstituted products of 2,4,6-bromoaniline and 2,4,6-bromophenol according to the melting point ranges obtained. This supports predictions that these aminoalkane and hydroxyl groups would be the strongest activating groups of benzene. Anisole yielded a disubstituted product which suggests that it is a more have activator when compared to aniline and phenol. Acetamide, which has the bulkiest substituent, yield a monosubstituted product which suggests that it is the weakest activator of the four. These res ults match up with ranking predictions but differ with substituent predictions. It was predicted that anisoles activating say-so would be on par with that of phenol and aniline when results indicate that it is actually substantially weaker. Sources of ErrorAfter recrystallzation and weighing out the final product identified as 4-bromoacetamide. It was observed that the actual yield was high than the theoretical yield. This could have been due to impurities in our final product.