Glossary of Organic Chemistry II
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- When a benzene ring attacks an electrophile it adds the Electrophile to the dbl bond resulting in a carbocation transition state known as
- Sigma complex
- The sigma complex is/is not aromatic. why?
break in the conjugation of sp2 carbons. One carbon now becomes sp3 hybridized.
- Electrophillic aromatic substitution
- the substitution of a hydrogen proton with an electrophile (and regeneration of aromaticity).
- Bromination of benzene requires:
- Rate determining step of Electrophillic aromatic substitution
- formation of the sigma complex (b/c of loss of aromaticity)
- The second step of the mechanism is exothermic b/c:
- aromaticity is reobtained.
- Reagent for Chlorination of benzene
- ALCl3/ Cl2
- Reagents required for iodination of benzene
- I2/ HNO3
(to oxidize/used up in rxn)
- Nitration of benzene requires:
- Sulfonation of benzene requires:
SO3 good electrophile (w/ 4 resonance structures)
- Desulfonation of Benzenesulfonic acid requires
- H+/ heat
(follows the same mechanism as sulfonation in reverse)
- Ortho-para directors
- O- > R-N-R > OH > -OR > anilides> -R (no lone pairs) > Halogens
- Meta directors
- Nitro > cyano > SO3H > ketones > aldehydes > carboxyllic acids
- Halogens are
- Electron withdrawing by inductive effects but donating by resonance. Resonance > induction and therfore halogens are ortho-para directors.
- when activating and deactivating groups counter eachother in where to place substituents...
- the activating group (ortho-para usually wins)
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