Question
Identify the correct IUPAC name of hydrocarbon (x) containing three primary carbon atoms and with molar mass 72 g mol ^ -1 .
JEE Main
Chemistry
General Organic Chemistry
2026
JEE Main 2026 (05 April Shift 2)
JEE Main Chemistry Question (2026) — Solution
Options
- A. 1,1-Dimethylcyclopropane
- B. 2,2-Dimethylpropane
- C. 2-Methylbutane
- D. n-pentane
Answer
C. 2-Methylbutane
Step-by-step solution
Let the hydrocarbon be an alkane with general formula C_nH_ 2n+2 . Molar mass = 14n + 2 = 72 14n = 70 n = 5 The molecular formula is C_5H_ 12 . The structural isomers of C_5H_ 12 are: n-pentane: CH_3-CH_2-CH_2-CH_2-CH_3 (2 primary carbons) 2-methylbutane: CH_3-CH(CH_3)-CH_2-CH_3 (3 primary carbons) 2,2-dimethylpropane: C(CH_3)_4 (4 primary carbons) The hydrocarbon with exactly three primary carbon atoms is 2-methylbutane. Answer: 2-Methylbutane
Related: Chemistry — General Organic Chemistry · All PYQ Banks