Step 1: Identify the reaction type.
The azo compound shown is likely formed by a diazotization reaction involving ethylamine and CH\(_3\)CH\(_2\).
Step 2: Conclusion.
Thus, the starting reagents needed are CH\(_3\)CH\(_2\) and ethylamine.
Final Answer:
\[
\boxed{\text{CH}_3\text{CH}_2 + \text{ethylamine}}
\]