To solve this question, let's analyze the reactions of compound A based on the given information and deduce the correct order of A, B, and C.
- Compound A reacts with Na to form compound B. This typically indicates a reaction with an alcohol, as alcohol reacts with sodium to form an alkoxide and hydrogen gas. Therefore, A is likely ethanol, C_2H_5OH, and B would be sodium ethoxide, C_2H_5ONa.
- Compound A also reacts with PCl_5 to form compound C. Reactions of PCl_5 with alcohols typically yield alkyl chlorides and phosphorus oxychloride. Thus, C would be ethyl chloride, C_2H_5Cl.
- According to the information, compounds B and C react to produce diethyl ether, (C_2H_5)_2O. This reaction is consistent with the Williamson ether synthesis, where an alkoxide ion (from C_2H_5ONa) reacts with an alkyl halide (C_2H_5Cl) to form an ether.
From this analysis, we can conclude that the correct order of A, B, and C is:
C_2H_5OH, C_2H_5ONa, C_2H_5Cl.
The correct answer is thus the option: C_2H_5OH, C_2H_5ONa, C_2H_5Cl.