**Question:** 3. An amino acid has a –CH₂CH₃ side chain. What type of side chain could form hydrogen bonds with this side chain?**Options:** a. –CH₂–OH b. - –CH₂ - (benzene ring)c. - –CH₂–C(=O)–NH₂ d. none of the above**Explanation of Options:**- Option (a) features a side chain ending with a hydroxyl (-OH) group, which is capable of engaging in hydrogen bonding due to the presence of the electronegative oxygen atom.- Option (b) has a benzene ring, which primarily engages in aromatic interactions and is not typically involved in hydrogen bonding.- Option (c) presents an amide group (-C(=O)–NH₂), which can participate in hydrogen bonding through its carbonyl and amine groups.- Option (d) suggests that none of the above options are capable of forming hydrogen bonds with the given side chain.**Diagram Explanation:**The structures illustrate chemical side chains with potential functional groups that might engage in various types of chemical bonding, including hydrogen bonds. These structures are depicted in a standard chemical notation to represent the molecular configuration accurately.

Hydrogen bond is the weak electrostatic force of attraction between covalently bonded hydrogen atom of one molecule and a highly electronegative atom (F,O,N) of another molecule. For example H-bond in serine(amino acid) is shown below: In this case intermolecular H-bond exists between covalently bonded H-atom of -O-H group and the highly electronegative atom that is O-atom.Given, the amino acid has : -CH2CH3 side chain. Though in this group, H-atoms are present but they are not attached to electronegative atom like F or O or N and one more thing is the electronegativity of Carbon and hydrogen is almost similar. So, this cannot form any partially positive hydrogen atom. So, this group cannot form H-bond with other groups. The amino acid side chain with -CH2CH3 cannot form H-bond with other groups. Answer: Option: d. none of the above.