Lab 4 Nitration of Methyl Benzoate.pdf

Lab 4 Nitration of Methyl Benzoate.pdf - Nitration of...

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N OH O O N OH 2 O O S O O OH O H N O O H 2 O HSO 4 Nitration of Methyl Benzoate Pre Lab Assignment: Complete the pre-lab cover page. Draw the mechanism of the reaction you will complete in lab. Use the proper arrow drawing convention to show all bond making and bond breaking steps in the reaction. Include all intermediates, including resonance structures. Learning Goals: Introduce electrophilic aromatic substitution Understand how substituent groups affect aromatic substitution Introduction: When an aromatic compound such as benzene reacts with an electrophile (E + ), it undergoes an electrophilic aromatic substitution reaction. The mechanism is shown below. The electrophile accepts an electron from the π system of the aromatic ring to form a resonance stabilized carbocation. When the electrophile is added to benzene, it can substitute onto any carbon in the ring. If a substituent group is already present on the ring (a mono substituted aromatic system), it will direct substitution to a specific carbon depending on whether the substituent is electron donating or withdrawing. In this experiment, you will be nitrating an aromatic ester. In most cases a Lewis acid catalyst must be added to form an electrophile that is strong enough to undergo substitution. The nitronium ion (NO 2 + ) is the electrophile and it is generated by reacting nitric acid with sulfuric acid (the catalyst) according to the following equilibrium reaction.
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Because nitric acid alone does not provide a concentration of the ions that is sufficient for the
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