Hydrocarbons are the parent compounds of all other organic compounds.

Answer

To justify the statement that "hydrocarbons are the parent compounds of all other organic compounds," we can break down the explanation into several steps:

### Step-by-Step Solution:

1. **Definition of Hydrocarbons**:
- Hydrocarbons are organic compounds that consist exclusively of hydrogen and carbon atoms. They serve as the fundamental building blocks of organic chemistry.

2. **Derivation of Other Organic Compounds**:
- Other organic compounds are derived from hydrocarbons through chemical reactions. This derivation typically involves the substitution of hydrogen atoms in hydrocarbons with other atoms or functional groups.

3. **Substitution Reaction Example**:
- Consider ethane (C2H6), a simple hydrocarbon. When ethane reacts with chlorine (Cl2) in the presence of sunlight, a substitution reaction occurs where one hydrogen atom is replaced by a chlorine atom, resulting in chloroethane (C2H5Cl).

4. **Formation of More Complex Compounds**:
- This substitution process can continue, leading to the formation of more complex compounds. For example, further substitution can lead to dichloroethane (C2H4Cl2) and trichloroethane (C2H3Cl3).

5. **Generalization of the Concept**:
- The process of replacing hydrogen atoms in hydrocarbons can also involve other functional groups, such as nitro groups (–NO2) or amine groups (–NH2), leading to a wide variety of organic compounds. This demonstrates that hydrocarbons serve as the foundational structure from which many other organic compounds are derived.

6. **Conclusion**:
- Therefore, hydrocarbons are considered the parent compounds of all other organic compounds because they can undergo various reactions to form a diverse range of organic substances by substituting hydrogen with other atoms or groups.