How do I compare the -M effect due aldehyde and a carboxylic acid? Which will have stronger mesomeric effect?

  • $\begingroup$ Nope ronith the link you gave gives -I order and not -M order $\endgroup$
    – Amit
    Commented May 3 at 6:17
  • $\begingroup$ @Ronith that is the inductive effect order. Mesomeric effect is different $\endgroup$ Commented May 3 at 13:15
  • $\begingroup$ oh my bad i am so sorry. $\endgroup$
    – Ronith
    Commented May 3 at 13:33

1 Answer 1


An aldehyde would surely have higher $-M$ effect than a carboxylic acid.

Because in a Carboxylic acid there is an $-OH$ group resonating with the $\ce{C=O}$. Hence lowering it's $-M$ effect on the other neighboring group.

Whereas in an aldehyde the $\ce{C=O}$ have more electrophilic nature than carboxylic acid and hence have higher $-M$.



Carboxylic Acid

$$Carboxylic Acid$$


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