An unknown compound,B,has the molecular formula C₇H₁₂.On catalytic hydrogenation 1 mol of B absorbs 2 mol of hydrogen and yields 2-methylhexane.B has significant IR absorption band at about 3300 and 2200 cm^-1.Which compound best represents B? A)3-methyl-1-hexyne B)5-methyl-2-hexyne C)5-methyl-1,3-hexadiene D)5-methyl-1-hexyne E)2-methyl-1,5-hexadiene

Question

Quizplus · Accepted Answer

The molecular formula of the unknown compound indicates that it has 1 carbon-carbon triple bond and 17 carbon-carbon single bonds. The IR absorption band at 3300 cm^-1 indicates the presence of a C-H bond, likely an alkyne C-H bond, and the band at 2200 cm^-1 indicates the presence of a C≡C bond. Only choice D, 5-methyl-1-hexyne, fits this criteria as it has one triple bond and 17 single bonds, and also has a C-H bond and a C≡C bond that would give rise to the observed IR bands. Catalytic hydrogenation of 5-methyl-1-hexyne would produce 2-methylhexane as stated.

An Unknown Compound,B,has the Molecular Formula C7H12

An Unknown Compound,B,has the Molecular Formula C₇H₁₂