Arrange the following in the increasing order of their boiling points
(A) $n-C_4H_9NH_2$
(B) $(C_2H_5)_2NH$
(C) $n-C_4H_9OH$
(D) $C_2H_5N(CH_3)_2$
Choose the correct answer from the options given below:
Answer & explanation
Correct answer: option 4
The correct answer is Option (4) → (D), (B), (A), (C)
Boiling point mainly depends on hydrogen bonding strength and molecular structure.
Strength of intermolecular forces: Alcohols > Primary amines > Secondary amines > Tertiary amines
REASON
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Alcohols (–OH) form the strongest hydrogen bonding.
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Primary amines (–NH₂) can form more hydrogen bonds than secondary amines.
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Secondary amines (–NH) form fewer hydrogen bonds.
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Tertiary amines have no N–H bond, so they cannot form intermolecular hydrogen bonding.
(D) C₂H₅N(CH₃)₂
Tertiary amine → weakest intermolecular attraction → lowest boiling point
(B) (C₂H₅)₂NH
Secondary amine → moderate hydrogen bonding - Boiling point higher than tertiary amine.
(A) n-C₄H₉NH₂
Primary amine → stronger hydrogen bonding - Boiling point higher than secondary amine.
(C) n-C₄H₉OH
Alcohol → strongest hydrogen bonding → highest boiling point
D < B < A < C is the increasing order of boiling points.