Question

Most of the lower amine and carboxylic acid exist in liquid state but amino acid where both amine group and carboxylic acid group is present in same molecule are crystaliine.this is due to

Answer 1

Lower amines and carboxylic acids exist in liquid state but amino acids, where both amine and carboxylic acid groups are present in the same molecule, are crystalline. This can be explained on the basis of intramolecular hydrogen bonding.

• Hydrogen bonding or H-bonding takes place between hydrogen and highly electronegative atoms such as fluorine, oxygen and nitrogen atoms.
• In amino acids both COOH and NH₂ groups are present in the same molecule.
• The H from the COOH and N from NH₂ form intramolecular H-bond.
• This causes the molecule to take a particular crystal structure which is quite stable.
• Due to the absence of both the groups in individual molecules, it does not happens in amines and carboxylic acids.