A nitrogen lone pair activates even more strongly
المؤلف:
Jonathan Clayden , Nick Greeves , Stuart Warren
المصدر:
ORGANIC CHEMISTRY
الجزء والصفحة:
ص482
2025-06-10
502
Aniline (phenylamine) is even more reactive towards electrophiles than phenols, phenyl ethers, or phenoxide ions. Because nitrogen is less electronegative than oxygen, the lone pair is higher in energy and so even more available to interact with the π system than is the lone pair on oxygen. Reaction of aniline with bromine is very vigorous and rapidly gives 2,4,6-tri bromoaniline. The mechanism is very similar to the bromination of phenol so we show only one ortho substitution to remind you of how it goes.
The 1H NMR spectrum of aniline supports the increased electron density in the π system— the aromatic protons are even less deshielded than those of phenol as a result. Just how good nitrogen is in donating electrons into the π system is shown by comparing the relative rates for the bromination of benzene, methoxybenzene (anisole), and N, N dimethylaniline.
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