Arrange the following in increasing strength of carboxylic acid with respect to chloro-substituted acids?
Correct answer: D. CH3COOH<CH2ClCOOH<CHCl2COOH<CCl3COOH
- A. CCl3COOH<CHCl2COOH<CH2ClCOOH<CH3COOH
- B. CHCl2COOH<CH2ClCOOH<CH3COOH<CCl3COOH
- C. CH2ClCOOH<CH3COOH<CCl3COOH<CHCl2COOH
- D. CH3COOH<CH2ClCOOH<CHCl2COOH<CCl3COOH
Explanation
The acidity of carboxylic acids is influenced by the presence of electron-withdrawing groups, such as chlorine atoms. The more chlorine atoms present, the stronger the acid. This is because chlorine is highly electronegative, and it stabilizes the negative charge on the carboxylate ion through inductive effects, making the acid stronger. Therefore, the correct order from weakest to strongest acid is: CH3COOH (acetic acid, no Cl) < CH2ClCOOH (monochloroacetic acid, one Cl) < CHCl2COOH (dichloroacetic acid, two Cl) < CCl3COOH (trichloroacetic acid, three Cl). Other options are incorrect because they do not follow this trend.
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About Reactivity of Carboxylic Acids
Carboxylic acids show acidic behaviour because their carboxylate ions are resonance-stabilised, and electron-withdrawing groups can change their strength. Reactions include neutralisation, esterification, formation of acid chlorides and amides, reduction, decarboxylation and substitution at the acyl carbon, which differs from the reactions of phenols.
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