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Electrophilic Aromatic Substitution Formal Lab Essay

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Electrophilic Aromatic Substitution
Objective
The objective of this experiment was to illustrate electrophilic aromatic substitution by synthesizing p-nitroanilide (as well as ortho) from acetanilide by nitration. The para form was separated from the ortho form based on solubility properties using recrystallization techniques.
Synthetic equations:

Physical Properties & Hazards of Reagents/Products: (all taken from Sigma-Aldrich website)

Acetanilide
MM = 135.16 g/mol
Melting point = 113-115°C
Hazards: acute toxicity

Sulfuric acid
MM = 98.08 g/mol
Boiling point = 290°C
Density = 1.840 g/mL
Hazards: corrosive to metals and skin, serious eye damage

Nitric acid
MM = 63.01 g/mol
Boiling point = 120.5°C
Density = …show more content…

Discussion Aromatic compounds can undergo electrophilic substitution reactions. 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. Due to the fact that the conjugated 6π-electron system of the aromatic ring is so stable, the carbocation intermediate loses a proton to sustain the aromatic ring rather than reacting with a nucleophile. Ring substituents strongly influence the rate and position of electrophilic attack. Electron-donating groups on the benzene ring speed up the substitution process by stabilizing the carbocation intermediate. Electron-withdrawing groups, however, slow down the aromatic substitution because formation of the carbocation intermediate is more difficult. The electron-withdrawing group withdraws electron density from a species that is already positively charged making it very electron deficient. Therefore, electron-donating groups are considered to be “activating” and electron-withdrawing groups are “deactivating”. Activating substituents direct incoming groups to either the “ortho” or “para” positions. Deactivating substituents, with the exception of the halogens, direct incoming groups to the “meta” position. The experiment described above was an example of a specific electrophilic aromatic

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