Question 14 Marks
Give reason :
$(i)$ The boiling point of ethanol is higher than that of hydroxymethane.
$(ii)$ Phenol is a stronger acid than alcohol.
$(iii)$ Ethanol easily dissolve in water.
$(i)$ The boiling point of ethanol is higher than that of hydroxymethane.
$(ii)$ Phenol is a stronger acid than alcohol.
$(iii)$ Ethanol easily dissolve in water.
Answer
View full question & answer→$(i)$ Because of the presence of the $OH$ group in ethanol, intermolecular $H-$bonding occurs, resulting in molecule interaction. To break these hydrogen bonds, more energy is required. Methoxymethane, does not undergo hydrogen bonding. As a result ethanol has a higher boiling point than methoxymethane.
$(ii)$ Ethanol forms hydrogen bond with water molecules due to which its solubility in water increases and hence it easily dissolves in water.
$(iii)$ The ionisation of an alcohol and phenol takes place as follows:
Phenoxide ion obtained due to the ionisation of phenol is stable due to its resonance $(+M$ effect$).$
Because of the higher electronegativity of $sp^2$ hybridised carbon of phenol to which $-OH$ is attached the electron density decreases an oxygen, this increases the polarity of $-OH$ bond due to which its ionisation increases. This sequence does not happens in alcohol, hence phenol is more strong acid as compared to alcohol.
$(ii)$ Ethanol forms hydrogen bond with water molecules due to which its solubility in water increases and hence it easily dissolves in water.
$(iii)$ The ionisation of an alcohol and phenol takes place as follows:
Phenoxide ion obtained due to the ionisation of phenol is stable due to its resonance $(+M$ effect$).$
Because of the higher electronegativity of $sp^2$ hybridised carbon of phenol to which $-OH$ is attached the electron density decreases an oxygen, this increases the polarity of $-OH$ bond due to which its ionisation increases. This sequence does not happens in alcohol, hence phenol is more strong acid as compared to alcohol.
