Solutions_Manual_for_Organic_Chemistry_6th_Ed 373

Solutions_Manual_for_Organic_Chemistry_6th_Ed 373 - IS...

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17-6 (a) The key to electrophilic ARomAtic substItUtIon lIes In the stabil±ty of the sIgma complex. When tHe ElectrophIle Bonds At ort²o or PArA pos±tIons of ethylbenzene, the pos±t±ve chArge ±s shAred by the 3D c³rboN w±th the ethyl g´oupµ ¶ondi·g of t²e ElectrophIle At the metA posit±on lends no pARticulAR AdvantagE bEc¸usE tHE ¹oSItIve chºgE In the sIgma compLex Is nEver adjacent to» and tHErEfore never stAbIlIzed by¼ tHE Et½y¾ g¿OÀ¹Á ortHo CH 2 CH3 { CH 2 CH3 I  q à ; F eÂr3 - a: ± Ch + CH 2 C±3 I + C Q Âr H ²D-good (bÅ Ælectroph±l±c attack on ÇÈxyÉene gIVEs an IntErMED±atE In wH±cH only one of the threE rEson³ncE FÊrËs
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Unformatted text preview: IS stabIl±zeD by ³ substItuent Ìsee thE SoÍut±on to ÎrobÍEM 17È4ÅÏ ÐÈXyÍEÑeÒ HoÓeverÔ ±s StaB±ÍIzED ±n two oÕ its tHree resonance forÖsÏ × more stabÍe IntErmEd±³te g±Ves a faster re³ct±onÏ 1 7È7 Øor o´tHo anD pA´a attAck» tHe poS±tIVE chaÙge In tHE SIgMa coMplex can ÚE sHAÙed by resonancE wÛÜH the vInyl groupÏ ThIS c³nnot happen wÝtH Öeta attack bEcauSe tHe ¹osItIve cHArge Is never AdJ³cent Üo tHE vInyÍ groupÏ (Þrtho Attack Is shoÓn; para attack gIVEs an ±ntErMediate wIth posItIve c²AÙge on t²e s³ÖE carbonSÁ) ± 367 &} "extra ³ resOnance foR...
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This note was uploaded on 02/27/2010 for the course CHEM 140 taught by Professor Wade during the Spring '10 term at Whitman.

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