Question

Question: Into how many peaks will each proton shown in green be split?

a.

b.

c.

d.

e.

Image Caption

f.

Short answer

a. 3 and 4

b. 2 and 4

c. 1, 3, and 3

d. 2 and 2

e. 2 and 2

f. 2 and 3

Step-by-step solution

Chemical equivalence and the number of signals

All the protons in identical chemical environments and hence have the same shielding constants are said to be chemically equivalent. They will give rise to only one absorption line in the NMR spectrum. Each chemically different kind of proton will have different peaks.

Determination of splitting pattern for a molecule

* Determine the number of different kinds of protons.

* non-equivalent protons on the same carbon or adjacent carbon atoms will split each other

* then apply the \({\rm{n + 1}}\) rule.

Finding the number of peaks into which each proton will split

Structural formula of a

\({{\rm{H}}_{\rm{a}}}\)has three peaks, and the splitting is triplet as the neighboring carbon has two hydrogen atoms.

\({{\rm{H}}_{\rm{b}}}\) has four peaks, and the splitting is quartet as the neighboring carbon has three hydrogen atoms.

Structural formula of b

\({{\rm{H}}_{\rm{a}}}\)has two peaks, and the splitting is doublet as the neighboring carbon has one hydrogen atom.

\({{\rm{H}}_{\rm{b}}}\) has four peaks, and the splitting is quartet as the neighboring carbon has three hydrogen atoms.

Structural formula of c

\({{\rm{H}}_{\rm{a}}}\)has one peak, and the splitting is singlet as the neighboring carbon has no hydrogen atom.

\({{\rm{H}}_{\rm{b}}}\)has three peaks, and the splitting is triplet as the neighboring carbon has two hydrogen atoms.

\({{\rm{H}}_{\rm{c}}}\) has three peaks, and the splitting is triplet as the neighboring carbon has two hydrogen atoms.

Structural formula of d

\({{\rm{H}}_{\rm{a}}}\)has two peaks, and the splitting is doublet as the neighboring carbon has two hydrogen atoms.

\({{\rm{H}}_{\rm{b}}}\) has two peaks, and the splitting is doublet as the neighboring carbon has two hydrogen atoms.

Structural formula of e

\({{\rm{H}}_{\rm{a}}}\)has two peaks, and the splitting is doublet as the neighboring carbon has two hydrogen atoms.

\({{\rm{H}}_{\rm{b}}}\) has two peaks, and the splitting is doublet as the neighboring carbon has two hydrogen atoms.

Structural formula of f

\({{\rm{H}}_{\rm{a}}}\)has two peaks, and the splitting is doublet as the neighboring carbon has two hydrogen atoms.

\({{\rm{H}}_{\rm{b}}}\) has three peaks, and the splitting is triplet as the neighboring carbon has two hydrogen atoms.