Arrange the following compounds in increasing order of their boiling…

The correct answer is Option (2) → (B) < (D) < (A) < (C)

Alcohols are held together by intermolecular hydrogen bonds, which ethers lack, so the ether boils lowest. Among the alcohols, the boiling point rises with the number of carbon atoms and falls with branching of the carbon chain, because both change the van der Waals forces.

(B) Methoxymethane, CH₃OCH₃ — lowest. It is an ether with no O–H group, so its molecules are not hydrogen bonded to one another; it is also the lightest compound of the set.

(D) 2-Methylpropan-2-ol, (CH₃)₃C–OH — second. It is an isomer of butan-1-ol (C₄H₉OH), but its carbon chain is branched. The molecule is more compact, its surface area is smaller and the van der Waals forces are weaker.

(A) Butan-1-ol, CH₃CH₂CH₂CH₂OH — third. The same four carbon atoms as (D), but in an unbranched chain.

(C) Pentan-1-ol, CH₃(CH₂)₄OH — highest. It has one carbon atom more than butan-1-ol, so the van der Waals forces are the strongest.

NCERT (2026-27 edition):
7.4.3 Physical Properties – “The boiling points of alcohols and phenols increase with increase in the number of carbon atoms (increase in van der Waals forces). In alcohols, the boiling points decrease with increase of branching in carbon chain (because of decrease in van der Waals forces with decrease in surface area).”

“The high boiling points of alcohols are mainly due to the presence of intermolecular hydrogen bonding in them which is lacking in ethers and hydrocarbons.”

7.6.2 Physical Properties – “The large difference in boiling points of alcohols and ethers is due to the presence of hydrogen bonding in alcohols.”