1559r.ch22.389-40910/19/0517:23Page394 394 chapter 22 CHEMISTRY OF BENZENE SUBSTITUENTS:ALKYLBENZENES,PHENOLS,AND BENZENAMINES 39.(a)One solution,perhaps a bit roundabout: 】CHa.A BrCHCHs K+-OC(CH: (CHaCOH CH=CH2 CH2CH2Br COOH . 一-○-00 0
Seven resonance forms make this carbanion especially stable. It is also aromatic, having 14 electrons in an unbroken loop of p orbitals. 39. (a) One solution, perhaps a bit roundabout: (b) (c) (d) CH3 Br Br Na2Cr2O7, H2SO4 product CH3 CH3 SO3H SO3H CH3 Br Br SO3, H2SO4 2 Br2, FeBr3 H2O, C COOH CH3OH, H O product C CH3 Na2Cr2O7, H2SO4 O CH3 COOH COCl SOCl2 KMnO CH3, AlCl3 4, HO, CH3 CH3 Cl Cl2, FeCl3 Na2Cr2O7, H2SO4, COOH Cl 1. SOCl2 2. NH3 product CH2CH2Br HBr, ROOR (Anti-Markovnikov) CH CH2 BrCHCH3 NBS, hv CH2CH3 K OC(CH3)3 (CH3)3COH CH3CH2Cl, AlCl3 394 • Chapter 22 CHEMISTRY OF BENZENE SUBSTITUENTS: ALKYLBENZENES, PHENOLS, AND BENZENAMINES 1559T_ch22_389-408 10/19/05 17:23 Page 394
1559T_ch22_389-40810/19/0517:23Pa9e395 ⊕ EQA Solutions to Problems.395 40 ing group 41.The presence of strong electror CH:O. Cl ortho or para to no?'s No. is most easily displaced NO CH Benzyne mechanism N(CHCH N(CH2CH) 42.aCCCettmote2eatKoe mide metRmmHoHad2a.aok ,H0,△ CH,CH2CH2CH2-Li* 入CH,CH,CH,CH CH.O CH2O-Li* H.H0,product CH2CH2CH2CHs Strongly basic butyllithium s HE in the firs
40. Most reactive ones have NO2 groups ortho or para to the leaving group. So, 41. The presence of strong electron-withdrawing groups such as NO2 ortho or para to a potential leaving group favors nucleophilic aromatic substitution by the addition–elimination mechanism. Without such groups in these positions, the benzyne mechanism is favored. (a) (b) (c) 42. (a) 1. CH3COCl (forms amide, reduces ring activation so that bromination in the next step can be controlled to attach just one Br to the ring instead of three), 2. Br2, CHCl3, 3. KOH, H2O, (hydrolyzes amide back to benzenamine); (b) 1. CF3CO3H, CH2Cl2, 2. Cl2, FeCl3; (c) KCN (nucleophilic aromatic substitution); (d) H, H2O, 43. Strongly basic butyllithium removes HF in the first step, generating benzyne. A second mole of butyllithium adds to benzyne as a nucleophile. The reason for the direction of addition is explained in the answer to Exercise 22-12. CH3O CH2CH2CH2CH3 CH2O Li H, H2O product CH3O CH2CH2CH2CH3 CH3CH2CH2CH2 Li Li OCH3 OCH3 C O H H CH3CH2CH2CH2 Li LiF butane F H N(CH2CH3)2 CH3 N(CH2CH3)2 CH3 Benzyne mechanism NO2 CH3O NO2 Cl Cl ortho or para to NO2’s is most easily displaced NO2 NO2 NHNH2 NO2 NO2 Br NO2 Br NO2 NO2 Br NO2 Br NO2 Br (Closer, so greater inductive effect) Solutions to Problems • 395 1559T_ch22_389-408 10/19/05 17:23 Page 395