Question

In the following structures, which two forms are staggered conformations of ethane? 

• A. 1 and 4
• B. 2 and 3
• C. 1 and 2
• D. 1 and 3

Hint:

Staggered conformation = minimum repulsion, maximum stability Eclipsed conformation = maximum repulsion, minimum stability

Answer 1

The Correct Option is C

Step 1: A staggered conformation is one in which the hydrogen atoms on the front carbon lie in between those on the rear carbon, giving maximum separation. 

Step 2: Analysis of the given figures: 
• Structure (1): Sawhorse representation with hydrogens alternating ⟹ staggered 
• Structure (2): Newman projection showing hydrogens exactly between each other ⟹ staggered 
• Structure (3): Newman projection with hydrogens aligned ⟹ eclipsed 
• Structure (4): Sawhorse representation with overlapping hydrogens ⟹ eclipsed 

Step 3: Hence, the staggered conformations are (1) and (2).