Question

Larger molecules have hydrogen-bonding networks that contribute to specific, high- affinity binding. Smaller molecules such as urea can also form these networks. How many hydrogen bonds can urea (Figure Q2-36) form if dissolved in water?

(a) 6
(b) 5
(c) 3
(d) 4

Answer 1

Urea, when dissolved in water, can form four hydrogen bonds due to its molecular structure allowing two hydrogen bonds as a donor and two as an acceptor. This contributes to urea's solubility and its physical properties in an aqueous solution.

Step-by-step explanation:

Hydrogen Bonding Ability of Urea

When dissolved in water, urea is capable of forming four hydrogen bonds. Urea can function as both a hydrogen bond donor and acceptor due to its amine and carbonyl functional groups. Specifically, urea has two nitrogen-hydrogen bonds that can act as hydrogen bond donors and one oxygen atom with a lone pair that can act as an acceptor for two hydrogen bonds. This is affirmed by examining the molecular structure of urea and recognizing the potential sites for hydrogen bonding interactions. Water molecules, which are highly capable of hydrogen bonding due to their polar nature, can readily interact with solutes like urea to form these bonds.

Notably, hydrogen bonds are weaker than covalent bonds but they still exert a considerable influence on the physical properties of a compound. In the case of water, a network of hydrogen bonds contributes to its unique properties, such as a higher boiling point compared to other molecules of similar mass that form fewer hydrogen bonds. Similarly, urea's solubility in water and its resultant interactions are significantly affected by its ability to engage in hydrogen bonding.