Question

The carboxylic acid which has maximum solubility in water is:
A.Phthalic acid
B.Succinic acid
C.Malonic acid
D.Salicylic acid

Answer 1

Hint: Salicylic acid has intramolecular hydrogen bonding. So, it is least soluble. Out of the first three acids malonic acid has the smallest non – polar alkyl part. And we know that the acid which has the smallest non – polar alkyl part is the most soluble.

Complete step by step answer:
A carboxylic acid is an organic acid that contains a carboxyl group \[\left( {C\left( { = O} \right)OH} \right)\] attached to an R-group.
Phthalic acid, also called 1, 2-benzenedicarboxylic Acid, colourless, crystalline organic compound ordinarily produced and sold in the form of its anhydride. Phthalic acid is very soluble in boiling water, \[18\dfrac{g}{{100}}\] mL, and is much less soluble in chilled \[\left( {{{14}^0}C} \right)\] water, \[0.54\dfrac{g}{{100}}\] mL. Thus, water is a very good recrystallization solvent for phthalic acid.
Succinic acid having electronegative oxygen atoms is polar and is soluble in water. Moreover, it has a hydrogen atom bonded to the oxygen atom and can form hydrogen bonding with the surrounding water molecules, which leads to increase in solubility.
Malonic acid, a polar molecule that is also able to ionize, was found to be soluble in water and methyl alcohol but insoluble in hexane. Finally, biphenyl, a very nonpolar molecule, was found to be soluble in hexane but insoluble in water and methyl alcohol.
Salicylic acid is not soluble in water because it is not polar, the way water molecules are.
We know that, With the increase in hydrocarbon portion solubility in water \[\left( {{H_2}O} \right)\] decreases.

Therefore, the correct answer is option (C).

Note: Carboxylic acids and their derivatives are used in the production of polymers, biopolymers, coatings, adhesives, and pharmaceutical drugs. They also can be used as solvents, food additives, antimicrobials, and flavourings.