Question

X 2 6. Which one of the following is the intermediate in the bromination of toluene? (a)! 9) (c) III (d) IV CH3 che CH3z + BH 7. Which is the correct order of reactivity of the following three compounds in brominaion reactions? Most reactive first, least reacting last. O CH 3 13 (m) 3>>>I (6) 1>3>2 () 1>3 () >>1>2 8. In the nitration of the following compound the bromine will add on which carbon? (a) 1 (b) 2 (c) 3 (d) 1 and 2 CH -CH3 9. Provide the major product that results when benzene is treated with the following sequence of reagents: 1. BrytFeBe followed by 2. HNO, +H.SO. () 1 (b) 2 (0)3 (d) both 1 and 3 146 (0) 2 (6 lente el both a and a 10. Which of the following is the best choice of reagents to effect the electrophilic iodination of an aromatic ring? (a) KI, acetone (b) . CH,CN (c) KI, HNO (d) , HNO, 11. The final product of the reactions of ten-Butylbenzene that forms after the following series of reactions is: (a) 1 (6) 2 (c)3 (d) 4 & 2 & us. Ja 4. SOH
6-11

Answer 1

6. Boomimation of tolueme is van daromatic electro- bbilia substitution Heaction, whose mechanismis emplained below Stel Generation of bromonium ion ( Electrophile) - Bu - Br + Fe Bry → By L Br - Fe Bra ВА" + Febr Step 2 Attack position hara - ion) of bromomium ion at Ortho- and of toluene (formation of aremium Сң TH SH By Bot Resonance Stabilization of aremium ion Attack at ortho- position - Ch Cthy 1H Br Br Resonance Stabilization of are mium ion Attack at para position

DATE .................. -CH IS an electrodoma ting group which releases electrons through Inductive effect and hypercom jugatiom Ontho - and bana- Sites are most favourable because the Arenium lon Is Stabilized by the electron Mieleasing, effects, as indicated by But in case of meta- site, no such stabilization is Observed - Br Therefore, & option I is uncorrect because the intermediate is resonance stabilized • option I is correct • Option is incorrect because meta-bromination is less likely. • Option TV is incorrect because it is not an Brominated Intermediate 1. As we have already discussed, the intermediate involved ņ bromimation is a Carbocation, an electron donating group (ERG) would stabilize it, while an electron a withdrawing group (EWG) would destabilize it, it can be concluded that the substrate having an EDG would react faster than the one having Elg, Now while - O-c-Cty - Ch 8 is an Ewg - 0 - Cth are EDG - - OCH is a better EDG which domates via mesomerle

DATE ellect while -oh domates via hybercom jugation and Inductive effect. Order of reactivity will be - Chi le coyrect answer is >220 a ttle by rebra Bromimation NO Br си, CH Durma the bromimation, a Carbocation will be generated Smce -C-Cheq_-No, are electron withdratong gyou þs, boomimation at Ortho - $ para position to these group will not be facile while brommation at meta position to these group and Ortho-to - Electron domatmy gooup) is fachle Position 7 is Or the to CH meta to - No 8 - E-ch therefore, Bert (am electrophile) will add to most electron sich 'Carbon atom o NO HNO + h Sou Byfe By A Mechanism. Bu But feber Br - Bu - Fe Bry → Bu + Pe Bry BY + HBr + Fe Bez This com is recomanee Stabilized

HNO teh soy No, the + 2 Hso S Co - Он NO₂ HSO + NO & Ho By is an electrom withdrawing group, position On the baxa are election deficient, and attack of RD (Electrophile )' is likely On meta position A NO Hsey A + H com NO NE HSO4 B This carbocation Ts Mesomomee Stabilized Correct option. (b) . 10: for electrophilie lodina Hom we require 1e en which can be produced by oxida Hon of I, by HNO. Therefore correct ophon 1sDL_| HNG

d 503 cone. H Soy I 50H Mechanism cato so HO - SoH is an election withdrawing group, -clo (Electrophile) attacks meta position to -SoH. when treated mation and with water results in desulpho- yields the final product, So Correct option is (b)