Department of Pre-University Education, KarnatakaPUC Karnataka Science Class 12
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The melting points and solubility in water of amino acids are generally higher than that of the corresponding halo acids. Explain. - Chemistry

The melting points and solubility in water of amino acids are generally higher than that of the corresponding halo acids. Explain.

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Solution 1

Both acidic (carboxyl) as well as basic (amino) groups are present in the same molecule of amino acids. In aqueous solutions, the carboxyl group can lose a proton and the amino group can accept a proton, thus giving rise to a dipolar ion known as a zwitter ion.

Due to this dipolar behaviour, they have strong electrostatic interactions within them and with water. But halo-acids do not exhibit such dipolar behaviour.

For this reason, the melting points and the solubility of amino acids in water is higher than those of the corresponding halo-acids.

Solution 2

The amino acids exist as zwitter ions, H3N+ — CHR-COO-. Due to this dipolar salt like character, they have strong dipole-dipole attractions. Therefore, their melting points are higher than corresponding haloacids which do not have salt like character.

Due to salt like character, amino acids intereact strongly with water. As a result, their solubility in water is higher than corresponding haloacids which do not have salt like character.

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APPEARS IN

NCERT Class 12 Chemistry Textbook
Chapter 14 Biomolecules
Q 4 | Page 417
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