Question

An aromatic hydrocarbon with a molecular formula of C₁₃H₂₀has an ¹H NMR spectrum with a signal at ~7 ppm that integrates to 5H. It also has two singlets; one of the singlets has 1.5 times the area of the second. What is the structure of the aromatic hydrocarbon?

Short answer

The possible structure for aromatic hydrocarbon is shown below.

Step-by-step solution

Explanation of C13H20 1H NMR spectra

¹H NMR spectrum with a signal at ~7 ppm that integrates to 5H indicate the compound is a monosubstituted benzene ring. There are 6C and 5H present in a monosubstituted benzene ring. Given aromatic hydrocarbon molecular formulae is C₁₃H₂₀. By subtracting the atoms of monosubstituted benzene ring from given formulae we get there are 7C and 15H substituent atoms are present in given compound. Given compound have two singlets indicate the presence of two carbon atoms is attached to its substituent. Hence, we can deduce the possible structure of aromatic hydrocarbon from these inferences

Possible aromatic hydrocarbon structure

Possible structure

One of the singlet with (9H) has 1.5 times area of the second singlet (9H) indicate the shown above is the correct structure.