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An optically active amino acid (A) can exist in three forms depending on the pH of the medium. If the molecular formula of (A) is C_(3)H_(7)NO_(2)write. (i) structure of compound (A) in aqueous medium. What are such ions called ? (ii) in which medium will the cationic form of compound (A) exist ? (iii) in alkaline medium, towards which electrode will the compound (A) migrate in electric field ? |
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Answer» Solution :(i)(A) is `CH_(3) - underset(NH_(2))underset(|)(CH) - COOH` In AQUEOUS MEDIUM, H of -COOH migrates to `- NH_(2)`, group giving dipolar form called zwitter ion. `CH_(3) -underset("zwitter ion")underset(+NH_(3)) underset(|)(CH) - COO^(-)` (ii) In acidic medium, the cationic form of (A) will exist. `CH_(3) -underset(+NH_(3)) underset(|)(CH) - COO^(-) + H^(+) to CH_(3)- underset("Ctionic form")underset(+NH_(3))underset(|)(CH) -COOH` (iii) In alkaline medium, it will be present in anionic form. `CH_(3) -underset(+NH_(3)) underset(|)(CH) - COO^(-) + OH^(+) to CH_(3)- underset("Anionic form")underset(NH_(2))underset(|)(CH) -COOH + H_(2)O` Therefore, in the ELECTRIC FIELD, the compound in the alkaline medium will migrate towards ANODE. |
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