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: Understanding the Concept
A secondary (2 degree) carbon is attached to exactly two other carbon atoms.

Step 2: Count in each option
Cyclohexane has six secondary ring carbons. In 1-ethyl-2,3,4-trimethylcyclohexane, ring carbons 5 and 6 and the CH2 of the ethyl group are secondary, giving three. In 2,4-dimethylheptane, carbons 3, 5 and 6 are secondary, giving three.

Step 3: Tetramethylcyclohexane
In 1,2,3,4-tetramethylcyclohexane, ring carbons 1 to 4 carry methyl groups and are tertiary. Only ring carbons 5 and 6 are secondary, so there are two.

Step 4: Compare the options
The second option has exactly two secondary carbons.

Final Answer:
1,2,3,4-Tetramethylcyclohexane has exactly two secondary carbon atoms. \[ \boxed{\text{(B) }\text{1,2,3,4-Tetramethylcyclohexane}} \]