Question

Label each set of chemically equivalent protons, using ‘a’ for the set that will be at the lowest frequency in the ${}^{\mathbf{1}}\mathbf{H}$NMR spectrum, ‘b’ for the next lowest, and so on. Indicate the multiplicity of each signal.

a.

b.

c.

d.

e.

f.

Short answer

a.

b.

c.

d.

e.

f.

Step-by-step solution

Step-by-Step SolutionStep 1: Identifying neighboring protons

Neighboring proton means a proton within the molecule. They may or may not be equivalent, which is the main cause for spin-spin coupling and splitting patterns.

a.

Neighboring protons (a)

In this compound, ‘a’ has three hydrogen atoms and neighboring carbon has one hydrogen atom.

b.

Neighboring protons (b)

In this compound, ‘a’ has two neighboring protons, ‘b’ has five neighboring protons, ‘d’ has two neighboring protons, and ‘c’ has no neighboring protons.

c.

Neighboring protons (c)

In this, ‘a’ has two neighboring protons, ‘b’ has single neighboring proton, ‘c’ has five neighboring protons, ‘d’ has two neighboring protons, and ‘e’ has six neighboring protons.

d.

Neighboring protons (d)

In this, ‘a’ has two neighboring protons, ‘b’ has five neighboring protons, ‘c’ has two neighboring protons, and ‘d’ has no neighboring protons.

e.

Neighboring protons (e)

In this, ‘a’, ‘b’, and ‘c’ has no neighboring protons.

f.

Neighboring protons (f)

In this, ‘a’ has four neighboring protons, ‘b’ has four neighboring protons, and ‘c’ has two neighboring protons.

Finding the number of splits

a. In this, ‘a’ forms doublet and ‘b’ forms septet. It is indicated as given below.

Splitting in (a)

b. In this, ‘a’ forms a triplet, ‘b’ forms a multiplet, ‘c’ forms singlet. and ‘d’ forms triplet. It is shown below.

Splitting in (b)

c. In this, ‘a’ forms triplet, ‘b’ forms doublet, ‘c’ forms multiplet, ‘d’ forms triplet, and ‘e’ forms septet. It is indicated as given below.

Splitting in (c)

d. In this, ‘a’ forms triplet, ‘b’ forms multiplet, ‘c’ forms triplet. and ‘d’ forms singlet. It is shown below.

Splitting in (d)

e. In this, a, b, and c forms singlet in this compound. It is indicated in the figure below.

Splitting in (e)

f. In this, ‘a’ forms quintet, ‘b’ forms multiplet, and ‘c’ forms triplet. It is shown in the figure below.

Splitting in (f)