Electrophilic aromatic substitution formal lab
Modern projects and experiments in organic chemistry 2E pp Due to the fact that the conjugated 6? You are on page 1of 2 Search inside document 18 July Professor Herrera. Electron-donating groups on the benzene ring speed up the substitution process by stabilizing the carbocation intermediate.
The remainder of the solid was recrystallized from hot ethanol.
The solid was collected by vacuum filtration and rinsed with cold water. The mixture was carefully swirled in an ice bath to ensure that the two concentrated acids were thoroughly mixed together.
P-nitroacetanilide is less polar than o-nitroacetanilide and was observed on the plate as the spot with the lower Rf value 0. This is undesirable and would have led to a mixture of products.
Electrophilic aromatic substitution pre lab
A TLC was performed on the crude solid, the recrystallized solid, and the filtrate from the recrystallization. This problem can be avoided by converting the amine group into an amide -NHCOCH3 in the case of acetanilide prior to the electrophilic aromatic substitution reaction. Therefore, the major product of the substitution was to the para-position, 4-bromoacetanilide. The moderately activating acetamide group is much more directing than the weakly deactivating methyl group, therefore substitution is most likely to occur ortho to acetamide at the 2-position. The electron-withdrawing group withdraws electron density from a species that is already positively charged making it very electron deficient. The protecting group can actually be easily removed after the substitution reaction to regenerate the original amine group if desired. The nitronium ion is a strong enough electrophile, and can react with the aromatic compound in this experiment Methyl benzoate to form an arenium ion intermediate. Discussion Aromatic compounds can undergo electrophilic substitution reactions. The drop-wise addition of the nitrating agent took approximately minutes. A mechanistic analysis of acetanilide electrophilic substitution reveals that acetanilide substitutes mainly at the para position because of resonance stabilization as nitrogen accepts an electron pair from the benzene ring and adopts a positive charge.
The reaction yielded both ortho and para-nitroacetanilide as products. In these reactions, the aromatic ring acts as a nucleophile an electron pair donor and reacts with an electrophilic reagent an electron pair acceptor resulting in the replacement of a hydrogen on the aromatic ring with the electrophile.
Electrophilic and nucleophilic aromatic substitution
Procedure: Safety Precaution: Use care when handling concentrated sulfuric and nitric acids. Each sample gave two distinct spots on the filter paper with Rf values of 0. The spectra from 1H NMR proton nuclear magnetic resonance analysis of 4-bromoacetanilide is provided in Figure 1. The moderately activating acetamide group is much more directing than the weakly deactivating methyl group, therefore substitution is most likely to occur ortho to acetamide at the 2-position. Therefore, the major product of the substitution was to the para-position, 4-bromoacetanilide. Substitution to the ortho-position experienced hinderance due to the large, bulky character of the acetamide group. Modern projects and experiments in organic chemistry 2E pp Conduct an electrophilic aromatic substitution reaction on microscale level. Aromatic substitution reactions are important synthetic reactions that are used to make a variety of products including high-performance plastics and acetylsalicylic acid more commonly known as aspirin. Run a TLC analysis of both your crude and recrystallized samples on the same TLC plate , by dissolving a small amount of each sample in ether, Use an hexane:ether solvent system. Reaction: Draw the structures of the reactant methyl benzoate, as the electrophile the nitronium ion, , and the product in your lab book. The percent yield
As low as the percent yield may have been, I feel confident that the final product was pretty pure.
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