Explain the reason for the following observations. (i) Phenol does not readily react with \(\mathrm{PCl}_{5}\) to form chlorobenzene but alcohols readily form alkyl chloride. (ii) o-nitrophenol is steam volatile and its solubility in water is less than that of p-nitrophenol.

In order to understand why phenol does not react readily with \(\mathrm{PCl}_{5}\) to form chlorobenzene while alcohols form alkyl chloride, we should compare the structure and reactivity of phenol and alcohols. Phenol consists of a hydroxyl group (-OH) attached to a benzene ring, while alcohols have a hydroxyl group (-OH) bonded to an alkyl group (R). When an alcohol reacts with \(\mathrm{PCl}_{5}\), the hydroxyl group (-OH) in the alcohol is replaced by a chlorine atom to form alkyl chloride (R-Cl). Phenol is a less reactive compound compared to alcohols due to the resonance stabilization provided by the benzene ring. In phenol, the oxygen atom in the -OH group donates its lone pair of electrons to the benzene ring, which results in resonance structures. This stabilizes the phenol and consumes the lone pair of electrons of the oxygen atom, which prevents it from reacting readily with \(\mathrm{PCl}_{5}\). In the case of alcohols, there is no such resonance stabilization, and the lone pair of electrons in the oxygen atom is available for reaction with \(\mathrm{PCl}_{5}\). This makes alcohols more reactive towards \(\mathrm{PCl}_{5}\), forming alkyl chloride readily.

To understand the difference in solubility and steam volatility between o-nitrophenol and p-nitrophenol, we need to examine their molecular structures and intermolecular interactions. o-nitrophenol has the nitro group (-NO2) and the hydroxyl group (-OH) bonded to adjacent carbon atoms in the benzene ring, whereas p-nitrophenol has the -NO2 and -OH groups bonded to carbon atoms that are opposite to each other on the benzene ring. The difference in the position of the -NO2 and -OH groups in o-nitrophenol and p-nitrophenol leads to different intermolecular interactions. In o-nitrophenol, the -OH and -NO2 groups are positioned such that they can form an intramolecular hydrogen bond within a single molecule, resulting in a weaker intermolecular hydrogen bonding between different o-nitrophenol molecules. In p-nitrophenol, the -OH and -NO2 groups are not close enough to form intramolecular hydrogen bonding, which allows intermolecular hydrogen bonding to be more prevalent between p-nitrophenol molecules. Due to the weak intermolecular hydrogen bonds in o-nitrophenol, it is steam-volatile, meaning it can easily be carried away by steam. Also, the weak intermolecular hydrogen bonding makes it less soluble in water compared to p-nitrophenol, which has stronger intermolecular hydrogen bonds that allow it to mix better with water.