Question

How many unique 1H NMR and 13C NMR signals exist for the following compounds?

How many unique 1H NMR and 13C NMR signals exist for the following compounds?

Answer 1

Concepts and reason

There are two types of nuclear magnetic resonance spectroscopy:

• ¹H NMR

• ¹³C NMR

• Both ¹H NMR and ¹³C NMR gives the information about nonequivalent protons or nonequivalent carbons present in the structure.

• The resonance frequency is observed with reference to the standard compound (0 ppm) is represented as chemical shift.

• When the protons or carbons have same environment, same chemical shift value is observed and the chemical shift value is measured in ppm.

Fundamentals

The protons with same environment:

In the above structure, all the 6 carbons are attached to protons but only 4 signals are observed in ¹H NMR because the right and left side of the protons have same environment. Therefore, those protons shows same chemical shift.

In the above structure, there are 6 carbons present but only 4 signals are observed in ¹³C NMR because, the right and left side of the carbons have same environment. Therefore, those carbons show same chemical shift.

¹H NMR:

¹³C NMR:

¹H NMR:

¹³C NMR:

¹H NMR:

¹³C NMR:

¹H NMR:

¹³C NMR:

¹H NMR:

¹³C NMR:

Ans:

The unique 1H NMR and 13C NMR signals shows for the given compounds are indicated below each structure.