Question

Identify the compound which has \(1^\circ\), \(2^\circ\), \(3^\circ\) and \(4^\circ\) carbons.

• A. 2,2,3,3-Tetramethylpentane
• B. 2,2-Dimethylpentane
• C. 2,2,3-Trimethylpentane
• D. 2-Methylpentane

Hint:

Always count the number of carbon atoms directly attached to a carbon atom to determine whether it is primary, secondary, tertiary or quaternary.

Answer 1

The Correct Option is C

Concept: Classification of carbon atoms: \[ 1^\circ : \text{attached to one carbon} \] \[ 2^\circ : \text{attached to two carbons} \] \[ 3^\circ : \text{attached to three carbons} \] \[ 4^\circ : \text{attached to four carbons} \]

Step 1: Examine 2,2,3-trimethylpentane.
Structure: \[ CH_3-C(CH_3)_2-CH(CH_3)-CH_2-CH_3 \] Here,

• Terminal methyl groups are \(1^\circ\) carbons.
• \(CH_2\) carbon is a \(2^\circ\) carbon.
• \(CH\) carbon attached to three carbons is a \(3^\circ\) carbon.
• Carbon at position-2 attached to four carbons is a \(4^\circ\) carbon.

Thus all four types are present. Hence, \[ \boxed{\text{2,2,3-Trimethylpentane}} \]