Question

Find the correct order of increasing boiling point in the following given molecules: (A) n-\( C_4 H_9 OH \)
(B) n-\( C_4 H_9 NH_2 \)
(C) n-\( C_4 H_{10} \)
(D) \( C_2 H_5 NH C_2 H_5 \)

• A. C<D<B<A
• B. A<B<D<C
• C. D<C<A<B
• D. B<C<D<A

Answer 1

The Correct Option is A

Step 1: General trend of boiling points.
Boiling point is influenced by molecular weight, molecular interactions (hydrogen bonding, dipole-dipole, and London dispersion forces), and the structure of the molecules. Molecules that exhibit hydrogen bonding typically have higher boiling points than those that do not.
Step 2: Analyzing the compounds.
- n-\( C_4 H_9 OH \) (A) is an alcohol (butanol) that has a hydroxyl group (-OH) capable of hydrogen bonding. Alcohols generally have higher boiling points due to hydrogen bonding. - n-\( C_4 H_9 NH_2 \) (B) is an amine (butylamine). Amines can form hydrogen bonds but generally have lower boiling points compared to alcohols due to weaker hydrogen bonding. - n-\( C_4 H_{10} \) (C) is an alkane (butane), which has only London dispersion forces. Alkanes typically have the lowest boiling points among the compounds given. - \( C_2 H_5 NH C_2 H_5 \) (D) is an amide (N,N-dimethylethanamine). Amides can also form hydrogen bonds, but the hydrogen bonding is weaker than in alcohols, making their boiling points typically lower than alcohols but higher than alkanes and amines.
Step 3: Order of boiling points.
The correct order of boiling points is: \[ C<D<B<A \] This is because alkanes have the lowest boiling points, followed by amides, amines, and alcohols, which have the highest boiling points due to stronger hydrogen bonding.
Step 4: Final Answer.
Thus, the correct answer is: \[ \text{(A) C<D<B<A} \]
Final Answer: C<D<B<A.