Ch 18 - Electeophilic Aromatic Substitution Flashcards
Halogenation EAS:
H ➡ X
Reagent?
X2/FeX3
What is EAS?
Substitute H on benzene with electrophile
Nitration EAS:
H ➡ NO2
Reagent?
HNO3/H2SO4
Sulfonation EAS:
H➡SO3H
Reagent?
SO3/H2SO4
FC Alkylation
H ➡ alkyl group (alkyl benzene)
Reagent?
RCl/AlCl3
•REARRANGEMENTS CAN OCCUR (H shift make more stable E+)
•RCl, or alcohol, alkene
FC Acylation
H ➡ O=C-R (ketone)
Reagent?
Acid chloride (RC(=O)Cl)/AlCl3
EAS general mechanism?
1) benzene + electrophile➡X=Y-Z+
2) X=Y-Z+ + base ➡ bezene ring restored, EAS Product
Electron donating groups?
- R groups - by induction, no resonance
* Z: group bonded to benzene (O or N) - by resonance
Electron withdrawing groups?
- Halogens - by induction (electronegativity)
* -Y=Z (EN: Z>Y, Y with full or partial + charge) by induction & resonance
Ortho, para directors? Activating or deactivating?
- Z: bonded to benzene (Z=O, N)
- R group (weakest activator)
- Halogens (deactivator)
Meta directors? Activating or deactivating?
- Y atom bonded to benzene with full or partial + charge (incl. SO3H, NO2, N(+)R3
- all deactivating
With OH, NH2 benzenes:
Reagents of monohalogenation? Polyhalogenation?
- poly - Br2/FeBr3
* mono - just Br2
FC rxns do not occur under what conditions?
- meta deactivator on ring
* NH2 on ring (LA/LB ➡ meta)
Halogenation of benzene, radical conditions?
Alkyl benzene ➡ benzylic bromide
Br2, light or heat/NBS, light, peroxides
Oxidation of alkyl benzenes: Alkyl benzene (primary or secondary) ➡ carboxylic acid)
Reagents?
KMnO4
Reduction of aryl ketones:
C=O ➡ CH2
Reagents?
- Clemmensen - Zn(Hg)/HCl (strong acid)
* Wolff-Kishner - NH2NH2/KOH (strong base)
Reduction of NO2 ➡ NH2
Reagents?
- H2, Pd-C
- Fe, HCl
- Sn, HCl
Which compounds absorb shortest wavelength of light? Longest wavelength?
- Shortest: most unconjugated (2 or more sigma bonds bet pi bonds)
- Longest: most conjugated (one sigma bond bet pi bonds)
