Given below are two statements:
Statement (I): The boiling points of alcohols and phenols increase with increase in the number of C-atoms.
Statement (II): The boiling points of alcohols and phenols are higher in comparison to other class of compounds such as ethers, haloalkanes.
In the light of the above statements, choose the correct answer from the options given below:
Statement (I): The boiling points of alcohols and phenols increase with increase in the number of C-atoms.
Statement (II): The boiling points of alcohols and phenols are higher in comparison to other class of compounds such as ethers, haloalkanes.
In the light of the above statements, choose the correct answer from the options given below:
- (A)Both Statement I and Statement II are false
- (B)Statement I is false but Statement II is true
- (C)Statement I is true but Statement II is false
- (D)Both Statement I and Statement II are true✓ Correct
Answer: (D)
Solution
Boiling point rises with molecular weight because larger molecules experience stronger van der Waals (London dispersion) attractions, so within a homologous series of alcohols and phenols boiling point increases steadily with the number of carbon atoms — methanol (65 °C) < ethanol (78 °C) < propan-1-ol (97 °C) < butan-1-ol (117 °C). Separately, the group in alcohols and phenols supports strong intermolecular hydrogen bonding, which raises their boiling points well above those of ethers or haloalkanes of comparable molar mass that lack an group — ethanol (78 °C) boils far higher than dimethyl ether ( °C) or chloroethane (12 °C) despite similar molecular weights. Both statements correctly describe the trend.
JEE Main · 2025 · 23 Jan 2025 · Shift 2 · Single correct option