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Chemistry Question on Organic Chemistry

The correct sequence of acidic strength of the following aliphatic acids in their decreasing order is: CH3CH2COOHCH_3CH_2COOH, CH3COOHCH_3COOH, CH3CH2CH2COOHCH_3CH_2CH_2COOH, HCOOHHCOOH

A

HCOOH>CH3COOH>CH3CH2COOH>CH3CH2CH2COOHHCOOH > CH_3COOH > CH_3CH_2COOH > CH_3CH_2CH_2COOH

B

HCOOH>CH3CH2CH2COOH>CH3CH2COOH>CH3COOHHCOOH > CH_3CH_2CH_2COOH > CH_3CH_2COOH > CH_3COOH

C

CH3CH2CH2COOH>CH3CH2COOH>CH3COOH>HCOOHCH_3CH_2CH_2COOH > CH_3CH_2COOH > CH_3COOH > HCOOH

D

CH3COOH>CH3CH2COOH>CH3CH2CH2COOH>HCOOHCH_3COOH > CH_3CH_2COOH > CH_3CH_2CH_2COOH > HCOOH

Answer

HCOOH>CH3COOH>CH3CH2COOH>CH3CH2CH2COOHHCOOH > CH_3COOH > CH_3CH_2COOH > CH_3CH_2CH_2COOH

Explanation

Solution

The acidic strength of carboxylic acids is influenced by the electron-withdrawing or electron-donating effects of alkyl groups:
HCOOH (formic acid) is the most acidic as it has no electron-donating alkyl group, which would reduce acidity.
CH3_3COOH (acetic acid) is less acidic because the methyl group (CH3_3) is weakly electron-donating.
CH3_3CH2_2COOH (propionic acid) is even less acidic due to the larger electron-donating ethyl group.
CH3_3CH2_2CH2_2COOH (butyric acid) is the least acidic because the longer alkyl chain has a stronger electron-donating effect.
The correct order of acidic strength is:
HCOOH > CH3COOH > CH3CH2COOH > CH3CH2CH2COOH.\textbf{HCOOH > CH$_3$COOH > CH$_3$CH$_2$COOH > CH$_3$CH$_2$CH$_2$COOH}.