See image — GOC and Organic Chemistry Basics Chemistry Question

💡 Solution & Explanation

Concept: Intermolecular hydrogen bonding requires a hydrogen atom bonded to a highly electronegative atom (F, O, or N) and a lone pair on an electronegative atom of a neighboring molecule. The strength of hydrogen bonding depends on the electronegativity and the partial positive charge on the H atom, which is influenced by the acidity/electron-withdrawing character of the group attached to O or N. Step 1 - Eliminate formaldehyde (c): Formaldehyde (HCHO) has a carbonyl group but no O-H or N-H bond, so it cannot act as a hydrogen bond donor. It cannot form intermolecular hydrogen bonds with itself. Step 2 - Compare the remaining candidates that have O-H or N-H bonds: - Methylamine (CH3NH2): Has N-H bonds. N is less electronegative than O, so N-H hydrogen bonds are weaker than O-H hydrogen bonds. - Methanol (CH3OH): Has an O-H bond. The methyl group is electron-donating, which slightly reduces the partial positive charge on H. - Phenol (C6H5OH): Has an O-H bond. The phenyl ring is electron-withdrawing through resonance (the lone pair on O delocalizes into the ring), which increases the partial positive charge on the O-H hydrogen and makes phenol more acidic than methanol (pKa ~10 vs ~15.5). A more acidic O-H means the H is more positively polarized, leading to stronger hydrogen bonding. Step 3 - Conclusion: Among all four options, phenol forms the strongest intermolecular hydrogen bonds because the aromatic ring withdraws electron density from oxygen via resonance, enhancing the δ+ on H and strengthening the O-H···O hydrogen bond compared to methanol or methylamine. Therefore, the correct answer is B.