Textbook Question
Predict the products formed when m-cresol (m-methylphenol) reacts with
(c) bromine in CCl4 in the dark
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19. Reactions of Aromatics: EAS and Beyond
Electron Withdrawing Groups
Multiple Choice
Rank the following in order of increasing rate of electrophilic aromatic bromination (slowest to fastest).
A
II < IV < I < III
B
I < II < IV < III
C
IV < III < II < I
D
III < II < I < IV
Verified step by step guidance1
Identify the substituents on each benzene ring: Compound I has a nitro group (NO2), Compound II has an aldehyde group (CHO), Compound III has a dimethylamino group (N(CH3)2), and Compound IV has a tert-butyl group (C(CH3)3).
Understand the effect of each substituent on the benzene ring: The nitro group is a strong electron-withdrawing group, the aldehyde group is a moderate electron-withdrawing group, the dimethylamino group is a strong electron-donating group, and the tert-butyl group is a weak electron-donating group.
Recall that electron-donating groups activate the benzene ring towards electrophilic aromatic substitution, while electron-withdrawing groups deactivate the ring.
Rank the compounds based on the activation or deactivation of the benzene ring: The compound with the strongest electron-donating group (III) will have the fastest rate of bromination, followed by the compound with the weaker electron-donating group (IV). The compound with the moderate electron-withdrawing group (II) will be slower, and the compound with the strong electron-withdrawing group (I) will be the slowest.
Based on the analysis, the order of increasing rate of electrophilic aromatic bromination is: I < II < IV < III.
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