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JEE Main levelSingle correct optionDifficulty 2 of 3bm062

Amino acids are crystalline solids with melting points much higher than those of haloalkanes or carboxylic acids of similar molar mass, mainly because

  1. Athey have very large molar masses
  2. Bthey exist as dipolar ions held together by strong electrostatic attractions in the crystal
  3. Conly van der Waals forces act between the molecules
  4. Dthe carboxyl group forms a dimer through hydrogen bonds

Answer: B

In the solid state amino acids exist as zwitterions , so the lattice is held by strong ion-ion (salt-like) attractions. This accounts for the high melting point and for solubility in water and low solubility in non-polar solvents.
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