Question

Identify the alkane having two secondary carbon atoms.:

• A. Cyclohexane
• B. 1,2,3,4-Tetramethylcyclohexane
• C. 1-Ethyl-2,3,4-trimethylcyclohexane
• D. 2,4-Dimethylheptane

Hint:

A secondary carbon is bonded to exactly two other carbon atoms; count them in each ring or chain.

Answer 1

The Correct Option is B

Step 1: Strategy
Count the ring carbons that are not substituted, since each of them has two ring neighbours and no other carbon.

Step 2: Apply
Cyclohexane gives 6. Substituting four consecutive carbons leaves only 2 unsubstituted ring carbons in the second option.

Step 3: Check the others
The ethyl group in the third option adds one more secondary carbon, giving 3, and 2,4-dimethylheptane has 3 as well. So only the second option has two.

Final Answer:
Only tetramethylcyclohexane has two unsubstituted ring carbons. \[ \boxed{\text{(B) }\text{1,2,3,4-Tetramethylcyclohexane}} \]