Step 1: Understanding the Concept:
The solubility of organic compounds in water heavily depends on their ability to form intermolecular hydrogen bonds with water molecules. The "like dissolves like" principle applies, meaning polar substances tend to be soluble in polar solvents (like water).
Step 2: Key Formula or Approach:
Compare the polarity and hydrogen-bonding capabilities of the functional groups in each class of compounds. The stronger the hydrogen bonding with water, the higher the solubility.
Step 3: Detailed Explanation:
Let's analyze the classes of compounds:
- Alcohols (\(\text{R-OH}\)): They have a highly polarized \(\text{O-H}\) bond due to the high electronegativity of oxygen. They can form strong hydrogen bonds with water molecules, making lower alcohols highly soluble.
- Amines (\(\text{R-NH}_2\)): They have an \(\text{N-H}\) bond. Nitrogen is less electronegative than oxygen, so the \(\text{N-H}\) bond is less polar than the \(\text{O-H}\) bond. While amines can form hydrogen bonds with water, these bonds are weaker than those formed by alcohols. Thus, amines are generally less soluble than corresponding alcohols of similar molar mass.
- Alkanes (\(\text{R-H}\)): These are non-polar hydrocarbons. They cannot form hydrogen bonds with water and only have weak van der Waals forces. Therefore, they are practically insoluble in water.
Based on the strength of interaction with water, the decreasing order of solubility is: Alcohols \(>\) Amines \(>\) Alkanes.
Step 4: Final Answer:
The correct option is (A).