Compounds with nearly identical molar masses often have very different physical properties. Choose the compound with the higher value for each of the following properties, and explain your choice. (a) Solubility in water: chloroethane or methylethylamine (b) Melting point: diethyl ether or 1 -butanol (c) Boiling point: trimethylamine or propylamine

Hydrogen bonding is a special type of intermolecular force that occurs when a hydrogen atom is directly bonded to a highly electronegative atom such as nitrogen, oxygen, or fluorine. This creates a strong attraction between molecules. For example, in water (H2O), each hydrogen atom is bonded to an oxygen atom, allowing water molecules to form hydrogen bonds with each other. This bonding significantly influences physical properties like boiling and melting points, and solubility.
Generally, the presence of hydrogen bonding increases the melting and boiling points of compounds because it requires more energy to break these bonds.
In the provided exercise, methylethylamine forms hydrogen bonds with water, making it more soluble than chloroethane, which cannot form hydrogen bonds.

The melting point of a substance is the temperature at which it changes from a solid to a liquid. Factors contributing to a higher melting point include stronger intermolecular forces and more organized molecular structures.
In the case of 1-butanol and diethyl ether, 1-butanol has the ability to form hydrogen bonds due to its hydroxyl group (-OH). These hydrogen bonds are significantly stronger than the van der Waals forces present in diethyl ether.
Because hydrogen bonds require more energy to break, 1-butanol has a higher melting point than diethyl ether.

The boiling point of a substance is the temperature at which it changes from a liquid to a gas. Similar to melting points, boiling points are influenced by the strength of intermolecular forces.
Stronger intermolecular forces require more energy to overcome, leading to higher boiling points. For instance, propylamine can form hydrogen bonds, which are more robust compared to the dipole-dipole interactions in trimethylamine.
Thus, the hydrogen bonding in propylamine results in a higher boiling point compared to trimethylamine.

Solubility measures how well a substance dissolves in a solvent, often water. Compounds that can form hydrogen bonds with water are generally more soluble.
In the exercise, methylethylamine can form hydrogen bonds with water due to the presence of a nitrogen atom, making it more soluble. Chloroethane, lacking a hydrogen-bond donor, cannot form these strong interactions, resulting in lower solubility in water.
Hydrogen bonding plays a crucial role in determining how substances dissolve, impacting many practical applications in chemistry and biology.

Intermolecular interactions are forces that hold molecules together within a substance. These include hydrogen bonds, dipole-dipole interactions, and van der Waals forces.
Hydrogen bonds are the strongest interaction among these three, significantly affecting properties like melting point, boiling point, and solubility. Dipole-dipole interactions occur between polar molecules, while van der Waals forces are the weakest and occur in all molecules regardless of polarity.
By understanding the type and strength of these interactions, one can predict and explain many physical properties of compounds, as illustrated by the comparative analysis of the substances in the exercise.