IIT JEE , AIEEE Forum - Chemistry , Organic Chemistry

urmilamip

Here in the fig. there is a +ve charge on CH2.
Which one is more stable? and sir plzzz explain in detail as to why the -I and -R power is maximum in 1st fig and least in bottom one.
in the book it is also written that in 2and fig the increase in +ve charge is only due to -I effect and not due to -R.

harsha_27

the inductive effect depends on distance and it decreases with distance .......so order of inductive effect is ortho>meta >para .......at para position u can almost neglect the inductive effect.......now coming to metameric effect(resonance effect),it doesn't depend on distance .its effect is equal everywhere and one more point is that it doesn't act in meta position to the group....because resonance doesn't reach there. only alternate positions are activated by metameric effect .....so at meta position only inductive effect exists ...no metameric effect.....coming to ur qn. the +ve charge on the carbon is destabilized by the -I and -R effect of the NO2 group so from the above explanation
at ortho .......both -R and -I
at meta ........only -I
at para.........-R with weak -I
so the order of stability is meta > para > ortho.......
rate me iff satisfied....

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