Please help me understand the electronic effects used to explain the acidity of benzoic acid. I was taught that there are two major effects namely: a) -I (negative inductive effect) b) +M (positive mesomeric effect). So my doubt is:

  1. COOH shows -I AND -M effect so, here are we talking with respect to -COOH or the phenyl group. Please explain why and also how to identify with respect to which group i'm supposed to look for other molecules as well.

  2. -I is shown by both COOH and Phenyl group. Now,for the above question if the -I effect (as my instructed by my teacher) shown by the molecule is w.r.t phenyl then how can we explain it w.r.t the inductive effect order i.e. -I shown by COOH is greater than that shown by phenyl so then the inductive effect of -COOH group should dominate and it will be like the phenyl group is donating or showing +I effect.

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    $\begingroup$ This should help: chemistry.stackexchange.com/questions/9334/… $\endgroup$
    – Buck Thorn
    Mar 25 at 16:20
  • $\begingroup$ Maybe you can choose a more descriptive title? Acidity of benzoic acid is only an indirect consequence of what you discuss in the question. $\endgroup$
    – Buck Thorn
    Mar 25 at 16:28
  • $\begingroup$ Thank you!Will try! $\endgroup$
    – chemguest
    Mar 25 at 17:30
  • $\begingroup$ You'll find a table here: en.wikipedia.org/wiki/Electrophilic_aromatic_directing_groups $\endgroup$
    – Buck Thorn
    Mar 25 at 17:36
  • $\begingroup$ There will be a mutual effect but here you are interested in the effect that the substituent on the aromatic ring has on substitution reactions (or other reactions) on the ring, so it is the M,I effect of the substituent on the ring that is of interest. Of course the substituent can be another ring. $\endgroup$
    – Buck Thorn
    Mar 25 at 18:41


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