Question

Number of primary carbon atoms present in 3-Ethyl-2,4-dimethyl heptane is

• A. 5
• B. 3
• C. 4
• D. 7

Hint:

Always count terminal \(\mathrm{CH_3}\) groups to identify primary carbon atoms.

Answer 1

The Correct Option is A

Step 1: Recall the definition of a primary carbon.
A primary carbon atom is a carbon that is attached to only one other carbon atom. Terminal \(\mathrm{CH_3}\) carbons are primary carbons.

Step 2: Write the carbon skeleton from the IUPAC name.
The parent chain is heptane (7 carbons). Substituents are: – An ethyl group at C-3 – Methyl groups at C-2 and C-4

Step 3: Count primary carbons.
Terminal carbons of the heptane chain \(= 2\)
Two methyl substituents contribute \(2\) primary carbons
The ethyl substituent contributes \(1\) terminal methyl carbon

Step 4: Total primary carbons.
\[ 2 + 2 + 1 = 5 \]

Step 5: Conclusion.
The number of primary carbon atoms present is \(5\).