1. Tardigrade
  2. Question
  3. Chemistry
  4. Consider the acid strength of the carboxylic acids: (i) PhCOOH (ii) o - NO2C6H4COOH (iii) p-NO2C6H4COOH (iv) m-NO2C6H4COOH

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Q. Consider the acid strength of the carboxylic acids:
(i) $PhCOOH$
(ii) $o - NO_2C_6H_4COOH$
(iii) $p-NO_2C_6H_4COOH$
(iv) $m-NO_2C_6H_4COOH$

COMEDKCOMEDK 2015Aldehydes Ketones and Carboxylic Acids

Solution:

Due to -I and -R effects of -N02 group, nitrobenzoic acids are stronger acids than benzoic acid. Due to ortho-effect, o-nitrobenzoic acid is the strongest acid.
In p-nitrobenzoic acid, both - R effect and -I effect of the $-NO_2$ group increase the acidity while in m-nitrobenzoic acid only the weaker - I effect increases the acidity. Hence, o-nitrobenzoic acid > p-nitrobenzoic acid > m-nitrobenzoic acid > benzoic acid.