Introduction

The reaction between phenol and PCl3 is not a viable method for the preparation of aryl halides. This is due to the nature of the reaction and the properties of the reactants involved. Let's explore the reasons in detail.

Explanation

1. Reaction Mechanism
When phenol reacts with PCl3, a substitution reaction is expected to occur. The lone pair of electrons on the oxygen atom of phenol can potentially attack the phosphorus atom of PCl3, leading to the formation of an intermediate.

2. Stability of the Intermediate
In the intermediate formed, the oxygen atom would be bonded to the phosphorus atom, resulting in a positively charged oxygen atom. This intermediate is highly unstable due to the presence of the positive charge on the oxygen atom. As a result, it readily decomposes, leading to the formation of a phenoxide ion and phosphoryl chloride.

3. Reactivity of Phenoxide Ion
The phenoxide ion formed in the previous step is a highly reactive species. It can undergo various reactions, including electrophilic aromatic substitution reactions. However, the formation of an aryl halide from the phenoxide ion requires the presence of a halogenating agent such as bromine or chlorine. PCl3, being a phosphorus halide, cannot act as a halogenating agent in this context.

4. Formation of Phosphoryl Chloride
The decomposition of the intermediate gives rise to phosphoryl chloride, which is a byproduct of the reaction. This byproduct makes the reaction highly inefficient for the preparation of aryl halides, as it does not contribute to the desired product.

Conclusion
In summary, the reaction between phenol and PCl3 does not lead to the formation of aryl halides due to the instability of the intermediate formed and the lack of halogenating properties of PCl3. Other methods, such as the use of halogenating agents, should be employed for the efficient preparation of aryl halides.