Electrophilic Aromatic Substitution

Conclusion:

In this experiment, two EAS reactions were performed and analyzed. The nitration of methyl benzoate formed the meta-nitration product 3-nitro methyl benzoate, according to NMR data. The Alkylation of m-xylene formed the 1,3,5-trisubstituted product, according to out-of-plane bending IR peaks.

Discussion:

In this experiment, two Electrophilic Aromatic Substitution (EAS) Reactions were performed and analyzed. The first EAS reaction was the nitration of methyl benzoate. The final recrystallized product weight was 0.307 g. The molecular weight was 182.16 g/mol. This calculated a theoretical yield of 0.4008 g and a percent yield of 76.6%. The melting point range was 79-80 deg C. The HNMR provided resulted in a meta-nitration product—3-nitro methylbenzoate. In this reaction, an excess of nitric acid and sulfuric acid were used; therefore, the major product was only mono-nitrated because the mono-nitration is strongly electron withdrawing. Excess sulfuric acid protonated the excess nitric acid to yield the nitronium cation. The nitronium cation was the nitrating electrophile. Excess sulfuric acid also pushed the equilibrium to the right in order to yield the nitronium cation. The second EAS reaction was the alkylation of m-xylene. The product molecular weight was 162.257 g/mol. This accumulated 0.206 g formed, or 0.00127 moles. Since the limiting reagent was 2-chloro-2-methylpropane, the theoretical yield was 0.73 g, which was used to calculate the percent yield as 28.2%. During the experiment, after 1ml of sat. sodium bicarb. was added, another ml was accidently added before the sat. sodium chloride; therefore, an extra extraction was done and accounts for much of the low percent. Also, while distilling the m-xylene, the temperature reached 200 deg C, or slightly above, probably causing some of the product to be distilled as well. There were 4 significant IR peaks that were taken into consideration. Peaks 691.7 and 768.5 cm-1 represented m-xylene starting material in the product; therefore, the reaction had to be heated to distill the m-xylene. Peaks 705.9 and 846.3 cm-1 were the C-H out-of-plane bending peaks that represented the substitution in the product; therefore, the product can be concluded as 1,3,5-trisubstituted. The expected substitution product would be 1,2,3-trisubstituted. Steric effect controlled the reaction outcome. The 1,2,3-trisubstituted product is a kinetic product and 1,3,5-trisubstituted is a thermodynamic product. The 1,2,4-trisubstituted product could have been obtained by using chloroethane instead of t-butyl chloride. The HNMR provided contains values for the aromatic proton peaks. These values were used to calculate coupling constants. The splitting patterns and oupling constants (J_ortho and J_meta) determined the position of the nitro group as meta.