Identify the correct IUPAC name of hydrocarbon ( x ) containing three primary carbon atoms and with molar mass 72 g mol ⁻¹ .

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 C₅H₁₂ . The structural isomers of C₅H₁₂ are: n-pentane: CH₃-CH₂-CH₂-CH₂-CH₃ (2 primary carbons) 2-methylbutane: CH₃-CH(CH₃)-CH₂-CH₃ (3 primary carbons) 2,2-dimethylpropane: C(CH₃)₄ (4 primary carbons) The hydrocarbon with exactly three primary carbon atoms is 2-methylbutane. Answer: 2-Methylbutane