What are hydrophobic molecules (or hydrophobic molecular regions)? What are hydrophilic molecules? How can they be described in relation to their polarity?
The Correct Answer and Explanation is :
Hydrophobic molecules, or hydrophobic molecular regions, are those that repel or do not interact favorably with water. These molecules are nonpolar, meaning they lack regions of positive or negative charge that could interact with the partially charged molecules of water. Hydrophobic substances are typically composed of nonpolar covalent bonds, where electrons are shared equally between atoms, resulting in no net dipole (separation of charge). Examples of hydrophobic molecules include oils, fats, and hydrocarbons.
In contrast, hydrophilic molecules are attracted to water and can dissolve or interact well in aqueous environments. These molecules are polar, meaning they have regions with partial positive and negative charges that can form hydrogen bonds or electrostatic interactions with water molecules. Hydrophilic substances generally contain functional groups like hydroxyl (-OH), amino (-NH2), or carboxyl (-COOH) groups that are capable of forming such interactions. Common examples of hydrophilic molecules include sugars, salts, and alcohols.
Polarity plays a key role in determining whether a molecule is hydrophobic or hydrophilic. Polar molecules, due to the presence of unequal electron sharing, tend to interact with water molecules through dipole-dipole interactions or hydrogen bonds. These interactions make the molecule soluble in water. On the other hand, nonpolar molecules do not form these types of interactions and thus remain insoluble or poorly soluble in water, making them hydrophobic.
In summary, hydrophobic molecules are nonpolar and repel water, while hydrophilic molecules are polar and interact favorably with water. Their behavior in aqueous environments is determined by the polarity of their bonds and the ability to form hydrogen bonds or other polar interactions with water molecules. This principle is fundamental in various biological and chemical processes, including cell membrane structure, protein folding, and solubility in solvents.