Question

The correct sequence of acidic strength of the following aliphatic acids in their decreasing order is: $CH_3CH_2COOH$, $CH_3COOH$, $CH_3CH_2CH_2COOH$, $HCOOH$

• A. $HCOOH > CH_3COOH > CH_3CH_2COOH > CH_3CH_2CH_2COOH$
• B. $HCOOH > CH_3CH_2CH_2COOH > CH_3CH_2COOH > CH_3COOH$
• C. $CH_3CH_2CH_2COOH > CH_3CH_2COOH > CH_3COOH > HCOOH$
• D. $CH_3COOH > CH_3CH_2COOH > CH_3CH_2CH_2COOH > HCOOH$

Answer 1

The Correct Option is A

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.
CH$_3$COOH (acetic acid) is less acidic because the methyl group (CH$_3$) is weakly electron-donating.
CH$_3$CH$_2$COOH (propionic acid) is even less acidic due to the larger electron-donating ethyl group.
CH$_3$CH$_2$CH$_2$COOH (butyric acid) is the least acidic because the longer alkyl chain has a stronger electron-donating effect.
The correct order of acidic strength is:
\[ \textbf{HCOOH > CH$_3$COOH > CH$_3$CH$_2$COOH > CH$_3$CH$_2$CH$_2$COOH}. \]