Which of the following statement about Hydrogen bonds is correct?

Question

BlackTom AI · Accepted Answer

A hydrogen bond is an attractive interaction in which a hydrogen atom covalently bonded to a strongly electronegative atom (donor: e.g., O–H, N–H, F–H) carries a partial positive charge and interacts with a lone pair of electrons on another electronegative atom (acceptor: e.g., O, N, F).

1. Relevant knowledge points and concepts
- Donor and acceptor: A hydrogen-bond donor is X–H where X is highly electronegative; an acceptor is an electronegative atom with a lone pair.  
- Nature and strength: Hydrogen bonds are mainly electrostatic (with some covalent character), weaker than covalent bonds (typical energies ≈ 4–40 kJ·mol−1) but stronger than dispersion forces.  
- Role in water: Extensive H-bonding controls water’s structure, high boiling point, surface tension, and density anomalies.

2. Step-by-step reasoning
- For an H bond to form, hydrogen must be attached to an electronegative atom, making the H partially positive.  
- That partially positive H is attracted to a lone pair on another electronegative atom. In effect the hydrogen is “shared” electrostatically between two electronegative centers (one via a covalent X–H, the other via a lone pair).  
- This sharing is why descriptions often say H is shared between two electronegative atoms.

3. Intermediate facts/calculations (illustrative)
- Example: In a water dimer, O–H covalent bond polarization gives δ+ on H; interaction O···H–O has energy ≈ 20 kJ·mol−1. Covalent O–H bond energy ≈ 460 kJ·mol−1 — showing H-bond is weaker but significant.

4. Why the correct answer is correct
- Option (a) captures the essential idea: an H that is polarized by one electronegative atom interacts (is shared) with another electronegative atom, producing a polar (electrostatic) interaction — i.e., a hydrogen bond.

5. Why other options are incorrect
- (b) “only requires a H-bond (e.g. OH, NH)” is incomplete: a donor group alone is not sufficient; an acceptor with a lone pair is also required.  
- (c) is false: water’s unique structure and properties depend strongly on hydrogen bonding.  
- (d) “only requires a H-bond acceptor” is also incomplete: an acceptor without a polarized H donor cannot form an H-bond.

6. Conclusion
- Therefore option (a) is correct, matching the provided answer.

Which of the following statement about Hydrogen bonds is correct?单项选择题

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