Arrange the following compounds in increasnig order of their boiling
CH_(3)CH_(2)CH_(2)CHO,CH_(3)CH_(2)CH_(2)CH_(2)OH,C_(2)H_(5)OC_(2)H_(5),CH_(3)CH_(2)CH_(2)CH_(2)CH_(3).

Solution :The molecular masses of all these compounds are comparable:
`CH_(3)CH_(2)CH_(2)CHO(72),CH_(3)CH_(2)CH_(2)CH_(2)OH(74),C_(2)H_(5)-O-C_(2)H_(5)(74),CH_(3)CH_(2)CH_(2)CH_(2)CH_(3)(72)`.
Butan-1-ol, i.e., `CH_(3)CH_(2)CH_(2)CH_(2)OH` UNDERGOES extensive intermolecular H-bonding, therefore, its boling POINT is the highest. Butanal is more polar than ethoxyethane, therefore, dipole-dipole interactions are stronger in `CH_(3)CH_(2)CH_(2)CHO` than in `C_(2)H_(5)OC_(2)H_(5)` and hence the b.p. of `CH_(3)CH_(2)CH_(2)CHO` is highest than that of `C_(2)H_(5)OC_(2)H_(5)`. further due to the presence of oxygen atom the molecules of `C_(2)H_(5)OC_(2)H_(5)` are little less symmetrical than those of n-pentane as a result, VAN der waals forces of attraction between molecules of `C_(2)H_(5)OC_(2)H_(5)` are slightly lower than those between molecules of n-pentane. hence, the b.p. of n-pentane is little higher than that of `C_(2)H_(5)OC_(2)H_5`. thus, the overall increasing order of boiliing points is:
`C_(2)H_(5)OC_(2)H_(5) lt CH_(3)CH_(2)CH_(2)CH_(2)CH_(3) lt CH_(3)CH_(2)CH_(2)CHO lt CH_(3)CH_(2)CH_(2)CH_(2)OH`
Please note that in N.C.E.R.T. test book, this order has been wrongly written as:
`CH_(3)CH_(2)CH_(2)CH_(2)CH_(3) lt C_(2)H_(5)OC_(2)H_(5) lt CH_(3)CH_(2)CH_(2)CHO lt CH_(3)CH_(2)CH_(2)CH_(2)OH`.