Question

Which of the following statements is/are correct?

• A. In an isoelectrolysis experiment, amino acids migrate at the isoelectric point towards electrodes
• B. p-aminobenzenesulphonic acid is a dipolar ion whereas p-aminobenzoic acid is not.
• C. ${\mathrm{H}}_3^{+}{\mathrm{NCH}}_2\mathrm{COOH}$(pka = 2.4) is more acidic than RCCOOH (pka = 4 - 5)
• D. Sulphanilic acid is insoluble in acid but soluble in base.

Answer 1

The Correct Option is B, C, D

Explanation:
(1) At isoelectric point, amino acid solution is neutral in nature.(2) p- aminobenzenesulphonic acid exists as dipolar ionIt is due to very high acidity of $-{\mathrm{SO}}_3\mathrm{H}$ group and stablisation of resulting dipolar iondue to charge distribution. In p-aminobenzoic acid, dipolar ion does not exist due to low acidity of - COOH group and less stablisation of dipolar ion, as negative chargedistribution.(3) since pKa of ${\mathrm{H}}_3^{+}{\mathrm{NCH}}_2\mathrm{COOH}$ is less than pKa of ${\mathrm{RCH}}_2\mathrm{COOH}$, it is more acidic.(4) Sulphanilic acid exists as dipolar ion.

It is an insoluble salt. It reacts with base as ${\mathrm{OH}}^{-}$ is more basic than $-{\mathrm{NH}}_2$But, it does not react with acid as ${\mathrm{H}}^{+}$ is less acidic than $-{\mathrm{SO}}_3\mathrm{H}$ group.