Question

How many ¹H NMR signals does each compound show?

a.

b.

c.

d.

e.

f.

g.

h.

Short answer

a. 2

b. 2

c. 2

d. 2

e. 4

f. 4

g. 5

h. 4

Step-by-step solution

NMR spectroscopy

Different types of proton NMR signals are observed in compounds due to the presence of different protons. The environment of these protons is affected by electron-withdrawing and electron-releasing groups.

 1H NMR signals in a, b, c, and d

a. The given compound has a plane of symmetry, as shown.

Plane of symmetry in a

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

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

Plane of symmetry in b

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

c. The given compound has a plane of symmetry, as shown.

Plane of symmetry in c

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

d. The given compound has a plane of symmetry, as shown.

Plane of symmetry in d

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

 1H NMR signals in e, f, g and h

e. The given compound has four types of protons, and it will give four signals.

Structure of e

f. The given compound has four types of protons, and it will give four signals.

Structure of f

g. The given compound has five types of protons, and it will give five signals.

Structure of g

h. The given compound has four types of protons, and it will give four signals.

Structure of h