JEE Chemistry 2023 Question with Solution

Given: The statements about arginine are to be checked.

Find: Which statement is not true for arginine.

Arginine is a basic amino acid containing an amino group, a carboxyl group, and a strongly basic guanidino side chain. Due to its ionic zwitterionic nature, it exists as a crystalline solid in the solid state. So statement A is true.

Amino acids like arginine are highly polar and exist in zwitterionic form. Therefore, they are soluble in water but insoluble or very poorly soluble in non-polar organic solvents such as benzene. So statement B is not true.

Because of strong electrostatic attractions between oppositely charged ions in the zwitterionic structure, arginine has a fairly high melting point. So statement C is true.

Arginine contains more than one ionisable functional group, namely $-COOH$, $-NH_2$, and guanidino group, so it shows more than one $pK_a$ value. So statement D is true.

Therefore, the incorrect statement is Option B.

Given: Arginine is an amino acid.

Find: The false statement.

Amino acids generally exist as zwitterions. Because of this, they are crystalline solids, have relatively high melting points, and show multiple acid-base dissociation constants. However, zwitterionic compounds are not highly soluble in non-polar solvents such as benzene.

Therefore, the false statement is B.