For each of the following pairs of compounds, predict which...

For each of the following pairs of compounds, predict which compound would exhibit stronger hydrogen bonding. Justify your prediction. It may help to write a Lewis formula for each. (a) water, $\mathrm{H}_{2} \mathrm{O}$, or hydrogen sulfide, $\mathrm{H}_{2} \mathrm{~S} ;$ (b) dichloromethane, $\mathrm{CH}_{2} \mathrm{Cl}_{2}$ or fluoroamine, $\mathrm{NH}_{2} \mathrm{~F} ;$ (c) acetone, $\mathrm{C}_{3} \mathrm{H}_{6} \mathrm{O}$ (contains a $\mathrm{C}=\mathrm{O}$ double bond) or ethanol, $\mathrm{C}_{2} \mathrm{H}_{6} \mathrm{O}$ (contains one $\mathrm{C}-\mathrm{O}$ single bond).

For each of the following pairs of compounds, predict which compound would exhibit stronger hydrogen bonding. Justify your prediction. It may help to write a Lewis formula for each. (a) water, $\mathrm{H}_{2} \mathrm{O}$, or hydrogen sulfide, $\mathrm{H}_{2} \mathrm{~S} ;$ (b) dichloromethane, $\mathrm{CH}_{2} \mathrm{Cl}_{2}$ or fluoroamine, $\mathrm{NH}_{2} \mathrm{~F} ;$
(c) acetone, $\mathrm{C}_{3} \mathrm{H}_{6} \mathrm{O}$ (contains a $\mathrm{C}=\mathrm{O}$ double bond) or ethanol, $\mathrm{C}_{2} \mathrm{H}_{6} \mathrm{O}$ (contains one $\mathrm{C}-\mathrm{O}$ single bond).

Key Concepts

Hydrogen Bonding

Hydrogen bonding is a special type of strong dipole?dipole interaction that occurs when a hydrogen atom is covalently attached to a highly electronegative atom like oxygen, nitrogen, or fluorine, and this hydrogen is attracted to a lone pair on another electronegative atom in a neighboring molecule. This interaction significantly influences the physical properties of substances, such as boiling points and solubilities.

Electronegativity

Electronegativity is a measure of how strongly an atom attracts electrons in a chemical bond. In the context of hydrogen bonding, atoms with high electronegativity create strong dipoles and increase the acidity of the hydrogen atoms attached to them, making these hydrogens more effective in forming hydrogen bonds.

Donor and Acceptor Capabilities

In hydrogen bonding, the molecule that provides the hydrogen is known as the hydrogen bond donor, while the molecule that accepts the hydrogen is the hydrogen bond acceptor, typically through a lone pair of electrons. The ability of a molecule to donate or accept hydrogen bonds depends on both its functional groups and the presence of electronegative atoms with available lone pairs.

Lewis Structures

Drawing Lewis structures helps visualize the arrangement of electrons in a molecule, indicating where lone pairs (potential hydrogen bond acceptors) and hydrogen atoms bonded to electronegative atoms (potential hydrogen bond donors) are located. This tool aids in predicting the number and strength of possible hydrogen bonding interactions.

Molecular Polarity and Intermolecular Forces

Molecular polarity arises from differences in electronegativity and the spatial arrangement of bonds within a molecule. Polarity is crucial in determining the types and strengths of intermolecular forces, such as dipole-dipole interactions and hydrogen bonding, which in turn affect the physical properties of substances.

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