# Which has more inductive effect: an aldehyde or a carboxylic acid?

A chemistry reference book that I have been reading gives the order of inductive effect ($-I$) as follows:

$\ce{-NH3+} > \ce{-NO2} > \ce{-SO2R} > \ce{-CN} > \ce{-SO3H} > \ce{-CHO} > \ce{-CO} > \ce{-COOH} > \ce{-COCl}> \ce{-CONH2} > \ce{-F} > \ce{-Cl} > \ce{-Br} > \ce{-I} > \ce{-OR} > \ce{-OH} > \ce{-NH2} > \ce{-C6H5} >\ce{-CH=CH2} >\ce{-H}$

The reference book has $\ce{COOH}$ ahead of $\ce{CHO}$ but Wikipedia has it the other way around. Which source is correct?

• And where will ester ( O-CO-CH3 ) lie in this order? – the.eleventh.letter Aug 24 at 4:09

$$\ce{COOH}$$ will show more -i effect than $$\ce{CHO}$$ because $$\ce{COOH}$$ hybridisation considering free radical as a sigma bond will be $$\ce{sp^2}$$ and both oxygen will also attract electron in angle 120° so that re will be more positive than aldehyde therefore it will attract electron more and show more -i effect.