To determine which compound exhibits the strongest intermolecular hydrogen bonding, we need to analyze the given options based on the presence of hydrogen atoms bonded to highly electronegative atoms (like oxygen, nitrogen, or fluorine) and the ability of these atoms to participate in hydrogen bonding.
### Step-by-Step Solution:
1. **Identify the Compounds:**
- Methylamine (CH₃NH₂)
- Phenol (C₆H₅OH)
- Formaldehyde (HCHO)
- Methanol (CH₃OH)
2. **Understanding Hydrogen Bonding:**
- Hydrogen bonding occurs when hydrogen is covalently bonded to an electronegative atom (like O, N, or F). The electronegative atom attracts the shared electrons, creating a partial positive charge on hydrogen, which can then interact with lone pairs on other electronegative atoms.
3. **Analyze Methylamine (CH₃NH₂):**
- In methylamine, hydrogen is bonded to nitrogen (N). While nitrogen is electronegative, it is less so than oxygen. Thus, methylamine can form hydrogen bonds, but the extent is limited compared to compounds with oxygen.
4. **Analyze Phenol (C₆H₅OH):**
- In phenol, the hydroxyl group (-OH) allows for hydrogen bonding. However, the lone pairs on the oxygen can participate in resonance with the aromatic ring, which can reduce the availability of the lone pairs for hydrogen bonding.
5. **Analyze Formaldehyde (HCHO):**
- In formaldehyde, the hydrogen is bonded to carbon, not to an electronegative atom. Therefore, it cannot participate in hydrogen bonding.
6. **Analyze Methanol (CH₃OH):**
- In methanol, the hydroxyl group (-OH) allows for strong hydrogen bonding. Oxygen is highly electronegative, which means it can create a significant partial positive charge on the hydrogen, making it a strong hydrogen bond donor.
7. **Comparison of Hydrogen Bonding Strength:**
- Methylamine: Moderate hydrogen bonding due to nitrogen.
- Phenol: Hydrogen bonding is present but reduced due to resonance.
- Formaldehyde: No hydrogen bonding.
- Methanol: Strong hydrogen bonding due to the presence of oxygen.
8. **Conclusion:**
- Among the given options, methanol (CH₃OH) exhibits the strongest intermolecular hydrogen bonding due to the high electronegativity of oxygen and the absence of resonance that would otherwise reduce hydrogen bonding capacity.
### Final Answer:
**The strongest intermolecular hydrogen bonding is found in: Methanol (CH₃OH).**
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