Question

Which of these species are capable of hydrogen bonding among themselves: (a) \(\mathrm{C}_{2} \mathrm{H}_{6},\) (b) \(\mathrm{HI},(\mathrm{c}) \mathrm{KF}\) (d) \(\mathrm{BeH}_{2},\) (e) \(\mathrm{CH}_{3} \mathrm{COOH} ?\)

Short answer

Among the listed compounds, only CH3COOH is capable of hydrogen bonding.

Step-by-step solution

Identify Compounds Capable of Hydrogen Bonding

The first step is to identify which of the given compounds contain hydrogen bonded to nitrogen (N), oxygen (O), or fluorine (F). From the list we have C2H6, HI, KF, BeH2, and CH3COOH.

Assess Each Compound Individually

(A) C2H6 - This compound has no N, O, or F, so it is not capable of hydrogen bonding. \( (B) HI \)- This compound has hydrogen, but it's not bonded to N, O, or F, so it can't form hydrogen bonds. \( (C) KF \)- Though this compound has F, it lacks H and therefore cannot form any hydrogen bonds. \( (D) BeH2 \) - Although this compound contains hydrogen, Be is not highly electronegative to form any hydrogen bonds. \( (E) CH3COOH \) - This compound contains hydrogen bonded to oxygen, so it is capable of hydrogen bonding.

Summarize Findings

After assessing each compound, it can be concluded that only CH3COOH is capable of hydrogen bonding among the given compounds.

Key concepts

Understanding Chemical Bonding

Chemical bonding refers to the force that holds atoms together to form molecules and compounds. There are three primary types of chemical bonds: ionic, covalent, and metallic. Ionic bonds occur between metals and nonmetals, involving the transfer of electrons and creating ions that attract one another. Covalent bonds are seen in compounds made of nonmetals where atoms share electrons, establishing molecules. Metallic bonds occur in metals, allowing electrons to move freely and providing metals with their characteristic properties, such as conductivity.

When considering hydrogen bonding specifically, it involves a subset of polar covalent bonds. This special interaction emerges when hydrogen is directly bonded to a highly electronegative atom, such as nitrogen (N), oxygen (O), or fluorine (F). This bond is particularly intriguing due to its influence on the physical properties of compounds, such as a higher boiling point and solubility.

Intermolecular Forces and Their Impact

Intermolecular forces are the forces that mediate interaction between molecules, influencing the physical state and properties of substances. These forces include London dispersion forces, dipole-dipole interactions, and hydrogen bonds. London dispersion forces are weak and occur in all molecules as a result of momentary uneven distribution of electrons. Dipole-dipole interactions occur between polar molecules, where the positive end of one molecule attracts the negative end of another.

Hydrogen bonding, however, is a special type of dipole-dipole interaction and one of the strongest intermolecular forces. It profoundly affects the properties of a substance, such as the high boiling point of water. Substances that can form hydrogen bonds showcase unique characteristics compared to those that cannot, owing to the strength of these bonds.

Molecular Polarity and Its Role in Hydrogen Bonding

Molecular polarity is a concept that describes the distribution of electrical charge over the atoms in a molecule. A molecule is polar if it has a region with a slight positive charge and another with a slight negative charge, creating a dipole. Polarity is determined by the difference in electronegativity between bonded atoms and the molecule's shape.

For hydrogen bonding to occur, the molecule must not only be polar but must also contain hydrogen bonded to either nitrogen, oxygen, or fluorine. For instance, in the exercise's solved problem, CH3COOH (acetic acid) features this kind of polarity, allowing it to participate in hydrogen bonding due to its oxygen-hydrogen bond, exemplifying the significance of molecular polarity in intermolecular interaction.