Arrange in increasing order of acidic strength , ch3cooh ,chcl2cooh,hcl,ccl3cooh and ch2clcooh
The correct answer and explanation is :
To arrange the given compounds in increasing order of acidic strength, we need to consider the effect of electron-withdrawing groups (EWGs) attached to the carboxyl group (-COOH), which can stabilize the conjugate base (carboxylate anion) and increase the acid strength. The stronger the electron-withdrawing ability of the substituent, the more acidic the compound will be. Here is the given list:
- CH₃COOH (Acetic acid)
- CHCl₂COOH (Dichloroacetic acid)
- HCl (Hydrochloric acid)
- CCl₃COOH (Trichloroacetic acid)
- CH₂ClCOOH (Chloroacetic acid)
Acid Strength Explanation:
- CH₃COOH (Acetic acid): Acetic acid is a weak acid with the -COOH group attached to a methyl group (-CH₃), which is an electron-donating group via inductive effects. This reduces the ability of the carboxylate anion to stabilize its negative charge, making it less acidic compared to other compounds with electron-withdrawing groups.
- CH₂ClCOOH (Chloroacetic acid): The -CH₂Cl group is an electron-withdrawing group through inductive effects, meaning it pulls electron density away from the carboxyl group, making the carboxylate anion more stable and thus increasing the acid strength. It is more acidic than acetic acid but less acidic than compounds with more electronegative substituents.
- CHCl₂COOH (Dichloroacetic acid): The presence of two chlorine atoms (-Cl) attached to the carbon adjacent to the carboxyl group provides a greater electron-withdrawing effect compared to a single chlorine atom. This increased withdrawal of electron density from the carboxyl group makes the conjugate base more stable, thereby increasing the acidic strength of dichloroacetic acid.
- CCl₃COOH (Trichloroacetic acid): The trichloro group (-CCl₃) has three chlorine atoms, which offer a very strong electron-withdrawing effect through both inductive and resonance effects. This extreme withdrawal of electron density stabilizes the conjugate base to a high degree, making trichloroacetic acid one of the strongest acids in the group.
- HCl (Hydrochloric acid): Hydrochloric acid is a strong acid and completely dissociates in water, making it far more acidic than any of the carboxylic acids listed above. Although it is not a carboxylic acid, it is included in the list, and its acidic strength is unmatched by any of the carboxylic acids due to its complete dissociation.
Increasing Order of Acidic Strength:
CH₃COOH < CH₂ClCOOH < CHCl₂COOH < CCl₃COOH < HCl
This order is based on the increasing electron-withdrawing effect of the substituents and the dissociation behavior of the compounds.