Preparation of Methyl M-Nitrobenzoate

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Preparation of methyl m-nitrobenzoate by nitration using methyl benzoate, nitric acid, and sulfuric acid

Aileen Quintana
TA: Sijie
Tues/Thurs 11:50

The purpose of this lab was to explore the concepts of electrophilic aromatic substitution, specifically nitration by synthesizing methyl m-nitrobenzoate using methyl benzoate, nitric acid and sulfuric acid. This nitration is a type of electrophilic aromatic substitution. A strongly charged electrophile, in this case a nitro group, replaces a proton on the aromatic ring. Aromatic compounds undergo substitution instead of addition to maintain resonance. The substituent on the benzene ring determines where the electrophile will add. Electron withdrawing substituents, like nitro group, withdraw electrons due to induction and direct position of the carbocation through resonance to add electrophile to meta position. Nitric acid, sulfuric acid, and methyl benzoate will be mixed and added to an ice bath. Crushed ice will be added to this cold mixture and form crystals.  After crystal product of m-methylbenzoate forms and purifies through recrystallization, its MP and IR will be taken to test purity and validate predicted position of the nitro group. Weight of final product will be compared to crude weight to determine effectiveness of procedure. It is possible to obtain small amounts of ortho and para isomers of nitrobenzoate and dinitration products. These will be removed when product is washed in methanol and purified. Ice added will be minimal because excess retards nitration by interfering with the nitric acid-sulfuric acid equilibria. The higher the temperature, the higher dinitration products formed. Since only one nitro group is desired, temperature should be maintained low to prevent dinitration (15 C ). The formation of the electrophile:

The mechanism:

Data and Calculations:
Table 1 provides the melting point and...