When your body metabolizes amino acids, one of the final end products is urea, a water so liable compound that is removed from the body as urine. Why is urea soluble in water, when hexamide, a related compound is not?
To understand why urea is soluble in water while hexamide is not, we need to consider their molecular structures and the intermolecular forces at play.
Urea (also known as carbamide) is a molecule with the chemical formula (NH2)2CO. It consists of two amino groups (NH2) connected to a carbonyl group (C=O). The presence of these polar groups (nitrogen and oxygen atoms) in urea allows it to form hydrogen bonds with water molecules.
On the other hand, hexamide (also called adipic dihydrazide) has the chemical formula (H2N-NH-CO)2. It contains two hydrazine groups (H2N-NH) connected by a carbonyl group (C=O). Hexamide lacks the presence of strongly polar functional groups that can readily form hydrogen bonds with water.
The solubility of a compound in water depends on the compatibility between the compound's intermolecular forces and those of water. Water molecules have polar covalent bonds, creating partial positive and negative charges. This polarity makes water an excellent solvent for polar compounds.
In the case of urea, its polar amino and carbonyl groups can interact with water molecules through hydrogen bonding, enabling urea to dissolve and form a homogeneous solution. The hydrogen bonds between urea and water molecules help to stabilize the solute-solvent interaction.
In contrast, hexamide lacks the necessary polar functional groups to form strong interactions with water molecules. As a result, the intermolecular forces between hexamide and water are weaker, leading to poor solubility.
In summary, urea is soluble in water due to its ability to form hydrogen bonds with water molecules, while hexamide lacks the necessary polar functional groups for strong interactions with water, making it insoluble.