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. H3+NCH2COOH(pka = 2.4) is more acidic than RCCOOH (pka = 4 - 5)
• D. Sulphanilic acid is insoluble in acid but soluble in base.

Answer 1

Answer: (B), (C), (D)

p-aminobenzenesulphonic acid is a dipolar ion whereas p-aminobenzoic acid is not.

Answer 2

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 −SO3H 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 H3+NCH2COOH is less than pKa of RCH2COOH, it is more acidic.(4) Sulphanilic acid exists as dipolar ion.It is an insoluble salt. It reacts with base as OH− is more basic than −NH2But, it does not react with acid as H+ is less acidic than −SO3H group.