Explain the following behaviours:

1. Alcohols are more soluble in water than the hydrocarbons of comparable molecular masses.

2. Ortho-nitrophenol is more acidic than ortho- methoxyphenol.

1. Solubility of alcohols are than those of hydrocarbons of comparable molecular masses. This is due to the formation of very stable intermolecular hydrogen bonding(bonding with other molecules of the same or different species). because of the presence of electronegative Oxygen atom and –OH group. So, due to the intermolecular hydrogen bonding, many similar molecules join with water molecules due to the formation of strong bonds. Due to which solubility in water increases.

No H atom is associated with Oxygen atom, so no intermolecular hydrogen bonding observed.

Due to all these reasons, these hydrocarbons have low boiling point as compared to their isomeric alcohols.

2. Acidity of a compound is determined by the stability of the conjugate base formed after losing a proton. Also we know that electron withdrawing group stabilises an anion better than an electron donating.

In these two compounds, ortho-nitrophenol is more acidic mainly due to the more stability of the conjugate base after compound loses a proton. In case of ortho-nitrophenol, the nitro group is attached to the benzene ring. We know, nitro group is electron withdrawing in nature, hence it stabilises the phenoxide ion. Thus ortho-nitrophenol is more acidic.

On other hand, in ortho-methoxy phenol, the methoxy group is attached to the benzene ring of phenol. We know, methoxy group is electron releasing group, thus it destabilises the phenoxide ion and decreases the acidic strength. Hence ortho-methoxy phenol is less acidic.