2444-111411

2444-111411 - Chlorination, Nitration, Sulfonation Cl Cl H...

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Chlorination, Nitration, Sulfonation Cl H Cl Cl chlorination NO 2 H NO 2 NO 2 nitration O 2 SOH H SO 3 H SO 3 H sulfonation O 2 SOH + HSO 4 = S OH O H O S O O O OH
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Reactions Cl 2 AlCl 3 Cl HNO 3 H 2 SO 4 NO 2 SO 3 H 2 SO 4 SO 3 H
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Activating and Deactivating 3 • The rate of reaction for generating the ortho and para products is faster than the rate for generating the meta product, so when X is electron releasing the major products should be ortho and para. • Based on this simple analysis, assume that the ortho and para arenium ions are about equal in energy, thee ortho and para products should be formed in roughly equal amounts in the absence of other mitigating factors. • When the substituent X has unshared electrons (O, N. halogen), it is possible to draw a fourth resonance contributor if there is a resonance contributor with the positive charge on the ipso carbon (ortho/para attack). The fourth resonance contributor is an indication of greater charge delocalization and greater stability for those arenium ions.
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Activating and Deactivating 4 X R O H O Cl O OH O Z ! ! + + + Electron Releasing Groups Electron Withdrawing Groups < SO 3 H < C " N < ortho, para products are major meta products are major Electron Releasing ability RO > HO > NHR > NH 2 > O O R N O R H (or R) > > alkyl Faster Rate of reaction slower rate of reaction BENZENE (reference Compound) react faster than benzene < < < NO 2 Electron withdrawing ability react slower than benzene Faster Rate of reaction slower rate of reaction Halogens (F, Cl, Br,. I) react slower than benzene but give orth/para products activators (faster) and ortho/para directors. deactivators (slower) and meta- directors.
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Activating and Deactivating 5 • The classifcation oF a group as deactivating simply means that the rate oF electrophilic aromatic substitution For a compound bearing that group is slower than the reaction with benzene itselF .
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This note was uploaded on 02/25/2012 for the course CHEM 244 taught by Professor Jardin,j during the Fall '08 term at UConn.

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2444-111411 - Chlorination, Nitration, Sulfonation Cl Cl H...

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