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I read a book on organic chemistry that stated that tosyl is better leaving group than benzenesulphonyl group, but it gave no reason for comparison. I think that benzenesulphonyl should be better leaving group since methyl group in tosyl should be destabilizing for the anion due to its +I and +R effect. I tried searching on the internet but it was of no help. Please give a reason why tosyl is better leaving group.

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First of all CH3 group dosent show +R effect in benzene system . Secondly Inductive effect wears out over distance and has maximum range of 4 carbons.The charge is delocalised on carbons which are unaffected by this effect so ultimately it has no role in destabilising the anion

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  • $\begingroup$ Doesn't methyl group show +R by hyper conjugation. $\endgroup$ – nikola Mar 13 '17 at 9:34
  • $\begingroup$ Hyperconjugation and resonnance are two different things askiitians.com/forums/Organic-Chemistry/21/39702/… $\endgroup$ – Supernova Mar 13 '17 at 9:35
  • $\begingroup$ moreover if the methyl group wants to hyperconjugate,the carbon on the benzene system bonded to it would become pentavalent $\endgroup$ – Supernova Mar 13 '17 at 9:37
  • $\begingroup$ Well, I was trying to say that methyl groups reduces the electron deficiency on benzene ring by hyper conjugation thereby reducing the -I effect of benzene ring. $\endgroup$ – nikola Mar 13 '17 at 9:37
  • $\begingroup$ please do explain how it can hyperconjugate @nikola $\endgroup$ – Supernova Mar 13 '17 at 9:38

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