Electrophilic Aromatic Substitution

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SUMMARY

The discussion centers on the Electrophilic Aromatic Substitution (EAS) reactions involving compounds P, Q, and S, subjected to nitration using an HNO3/H2SO4 mixture. The major products formed were determined based on the activating and deactivating effects of substituents. For compound P, the -OH group directs substitution to the ortho position, while for compound Q, the -OCH3 group also directs to the ortho position. In compound S, despite initial assumptions of the -OC=O group being electron-withdrawing, it is clarified that it acts as an electron-donating group, leading to substitution at the para position.

PREREQUISITES
  • Understanding of Electrophilic Aromatic Substitution (EAS) mechanisms
  • Knowledge of activating and deactivating groups in aromatic chemistry
  • Familiarity with resonance structures and their effects on electron density
  • Experience with nitration reactions using HNO3/H2SO4
NEXT STEPS
  • Study the effects of various substituents on EAS reactions
  • Learn about resonance structures and their influence on aromatic reactivity
  • Explore the differences between ortho, meta, and para substitution in aromatic compounds
  • Investigate the role of electron-withdrawing and electron-donating groups in organic reactions
USEFUL FOR

Chemistry students, organic chemists, and educators looking to deepen their understanding of Electrophilic Aromatic Substitution and the effects of substituents on aromatic reactivity.

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Homework Statement


The compounds P, Q and S, were separately subjected to nitration using HNO3/H2SO4mixture. The major product formed in each case respectively, is :
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1422961377168Capture.PNG


1422961398875Capture1.PNG

Homework Equations

The Attempt at a Solution


This is a standard EAS reaction. I know the answer will be either C or D, because in case of (P) -OH is more activating so the substitution will be with at ortho with respect to -OH (as para is blocked), similarly in case of (Q), it will be oath with respect to -OCH3 (more activating).
I don't understand what with respect to S. Is the -OC=O group electron withdrawing or donating? I thought it was withdrawing because the lone pair on oxygen is in resonance with the C=O bond (not with the benzene as the resonance with C=O is much more stable due to equivalent resonance structures (the reason why carboxylic acids are so stable). So, I thought the answer would be D and the substitution would occur at the meta position. But the answer is C. Help?
 
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Though O might undergo resonance with Carbonyl carbon, it's still a +R group for the second benzene ring making it more electron Rich and promoting Electrophile approach
How would you justify meta position?
 
Suraj M said:
Though O might undergo resonance with Carbonyl carbon, it's still a +R group for the second benzene ring making it more electron Rich and promoting Electrophile approach

Oh ok!
No meta then. I was thinking -I kind of thing. But got it!
 

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