CHM235LL - Infrared and Nuclear Magnetic Resonance Spectroscopy Practice Problem

Question

CHM235LL - Infrared and Nuclear Magnetic Resonance Spectroscopy Practice Problems: Answer the following questions for each structure given: How many types of H's are present (H environments/resonances/signals)? Predict the splitting pattern (multiplicity)...that is, is it a singlet, doublet, triplet, multiplet, etc. How many protons are giving off each signal? Give the simplest ratio of H's. Which H is most shielded? Deshielded? Please exclude OH's and NH's. How many types of C's are present (C environments/resonances/signals)?

Explanation / Answer

For a. structure

1. 5 types of H's

2. triplet for CH3 (3H); sextet for CH2 (2H); quintet for CH2 (2H); triplet for CH2 (2H); singlet for OH (1H)

3. Simplest ratio of protons - 3 : 2 : 2 : 2 : 1

4. The CH3 protons are most shielded and we have 3H like it

5. 4 types of C.

For structure b.

1. 4 types of H's

2. singlet for CH3 (3H); singlet for OH (1H); doublet for 2H aromatic ; doublet for 2H aromatic

3. Simplest ratio of protons - 3 : 1 : 2 : 2

4. The CH3 protons are most shielded and we have 3H like it

5. 8 types of C.

For structure c.

1. 5 types of H's

2. triplet for CH3 (3H); singlet for CH3 (3H); sextet for CH2 (2H) ; quintet for CH2 (2H); triplet for CH2 (2H)

3. Simplest ratio of protons - 3 : 3 : 2 : 2 : 2

4. The CH3 protons next to CH2 are most shielded and we have 3H like it

5. 6 types of C.

For structure d.

1. 2 types of H's

2. triplet for CH3 (3H); quartet for CH2 (2H)

3. Simplest ratio of protons - 3 : 2

4. The CH3 protons next to CH2 are most shielded and we have 3H like it

5. 3 types of C.

For structure e.

1. 2 types of H's

2. singlet for CH3 (9H); singlet for CH2 (2H)

3. Simplest ratio of protons - 9 : 2

4. The CH3 protons are most shielded and we have 3H like it

5. 3 types of C.

For structure f.

1. 6 types of H's

2. singlet for CH3 (3H); singlet for CH (1H) aromatic; doublet for CH (1H) aromatic); doublet for CH (1H) aromatic; doublet of doublet for CH (1H) aromatic; singlet for OH protons (1H)

3. Simplest ratio of protons - 3 : 1 : 1 : 1 : 1 : 1

4. The CH3 protons are most shielded and we have 3H like it

5. 7 types of C.

For structure g.

1. 4 types of H's

2. singlet for NH2 (2H); doublet for CH (2H) aromatic; doublet for CH (2H) aromatic); triplet for CH (1H) aromatic;

3. Simplest ratio of protons - 2 : 2 : 2 : 1

4. The NH2 protons are most shielded and we have 2H like it

5. 6 types of C.

For structure h.

1. 3 types of H's

2. singlet for OH (2H); doublet for CH (2H) aromatic; doublet for CH (2H) aromatic

3. Simplest ratio of protons - 2 : 2 : 2

4. The OH protons are most shielded and we have 1H like it

5. 3 types of C.

For structure i.

1. 2 types of H's

2. doublet for CH2 (2H); triplet for CH (1H)

3. Simplest ratio of protons - 2 : 1

4. The CH2 protons are most shielded and we have 2H like it

5. 2 types of C.

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