Question

How many ¹H NMR signals does each dimethylcyclopropane show?

Short answer

a. 2

b. 3

c. 3

Step-by-step solution

NMR spectroscopy

If a compound contains either plane of symmetry or center of symmetry, the protons of the opposite (mirror images) substituents have the same environment. Thus, these protons have given the same signal.

 1H NMR signals in a, b, and c

a. The given compound has a plane of symmetry as shown below:

Plane of symmetry in a

Thus, the given compound has two types of protons, and it will provide two signals.

b. The given compound has a plane of symmetry as shown below:

Plane of symmetry in b

Thus, the given compound has three types of protons, and it will provide three signals.

c. The given compound has a center of symmetry as shown below:

Center of symmetry in c

Thus, the given compound has three types of protons, and it will provide three signals.