Nitration of an Aromatic Ring

1. Introduction

Electrophilic Aromatic Substitution (EAS) is an organic reaction in which an electrophile substitutes a Hydrogen atom in an aromatic compound. It is very useful because substituted aromatic rings are often used as solvents and as important intermediates of many syntheses. The general form of the compound may be seen in equation 1 where Ar – H is an aromatic compound and E+ as any electrophile that may replace H+.

Ar – H        +        E+                        Ar – E               +        H+         (Equation 1)[pic 1]

An example of an EAS reaction is the Nitration of an aromatic ring, which is the primary step in order for the preparation of different organic compounds. In this exercise, you are going to prepare m-nitrobenzoic acid by reacting benzoic acid with a mixture of concentrated nitric and sulfuric acid. It is expected that you can write the general equation for the mechanism based on EAS.

The side reactions that may accompany the formation of m-nitrobenzoic acid given in equations 2 and 3:

[pic 2][pic 3]

[pic 4]

Equation 2:   Dintration to form                   3,5-dinitrobenzoic acid

1. Objectives

1. To prepare an aromatic nitro compound by means of an EAS reaction

1. To prepare m-nitrobenzoic acid from benzoic acid;
2. To recrystallize the crude product; and
3. To write the mechanism for the nitration of benzoic acid and the accompanying side reactions.

1. To compare the starting material and the product

1. To differentiate between m-nitrobenzoic and benzoic acid by using simple chemical tests.

1. Materials and Methods

1. Schematic Diagram of the Procedure

1. Synthesis and Isolation of M-Nitrobenzoic Acid
2. Chemical Test for the Comparison of Starting Material and Product

1. Test for unsaturated linkages
2. Reaction with Ferrous Chloride

Note: Should be freshly prepared!

1. Clean Up and Waste Management

1. Setup(s)

1. List of Necessary Chemicals

[pic 5]

Table 11.1. Data on the list of chemicals that will be used in the exercise.