Advanced Practical Organic Chemistry
The mechanism for the nitration is that of electrophilic aromatic
substitution. The nitronium ion is directed to the positions ortho and para
to the acetamido (-NHCOCH ) group. This occurs because the resonance 3
electron-releasing effect of that group increases the electron density at
those positions, helping to stabilize the intermediates that are formed.
Substitution para to the acetamido group is favour red over substitution
ortho to that group, because the great bulk of the acetamido group
shields the ortho positions from approach by reagents. This steric
hindrance makes ortho substitution much less likely than para
substitution, in which the bulk of the acetamido group has no influence.
The ortho substitution product is formed in small quantities in this
reaction.
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