Question

For the compounds:
(A) \( \text{H}_3\text{C} - \text{CH}_2 - \text{O} - \text{CH}_2 - \text{CH}_2 - \text{CH}_3 \)
(B) \( \text{H}_3\text{C} - \text{CH}_2 - \text{CH}_2 - \text{CH}_3 \)  
(C) \( \text{CH}_3 - \text{CH}_2 - \text{C} - \text{CH}_2 - \text{CH}_3 \)  
\(\ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ ||\ \)  
\(\ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \text{O}\ \)  

(D) \( \text{H}_3\text{C} - \text{CH} - \text{CH}_2 - \text{CH}_2 - \text{CH}_3 \)  
\(\ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ |\ \)  
\(\ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \text{OH}\ \)  
 
The increasing order of boiling point is: Choose the correct answer from the options given below:  

• A. (A)<(B)<(C)<(D)
• B. (B)<(A)<(C)<(D)
• C. (D)<(C)<(A)<(B)
• D. (B)<(A)<(D)<(C)

Answer 1

The Correct Option is B

Compounds having the same number of carbon atoms follow the boiling point order as:

\((\text{Boiling point})_{\text{Hydrogen bonding}} > (\text{Boiling point})_{\text{High polarity}} > (\text{Boiling point})_{\text{Low polarity}} > (\text{Boiling point})_{\text{Non-polar}}\)

Answer 2

Step 1: Classify each compound by intermolecular forces
(A) Ether (R–O–R′): has a polar C–O bond → dipole–dipole + London forces; no H-bond donors.
(B) Alkane (butane): nonpolar → only London dispersion forces (weakest among the four).
(C) Ketone (3-pentanone): carbonyl is more polar than ether → stronger dipole–dipole than (A) + London forces.
(D) Alcohol (1-pentanol): has –OH capable of intermolecular H-bonding → strongest intermolecular forces among the four.

Step 2: Note molecular-size effects (London forces)
Among species with similar polarity classes, larger molar mass/longer chain typically raises boiling point via stronger London forces. Here (B) is the smallest and nonpolar; (A), (C), (D) are C5 species, so their size is comparable and the dominant differentiator becomes the type/strength of intermolecular forces: alcohol H-bonding > carbonyl dipole > ether dipole > alkane.

Step 3: Order the boiling points
Thus, increasing order is:

(B) < (A) < (C) < (D)