Chapter 13, Problem 13.18P

What are the major IR absorptions in the functional group region for each compound?

a. d.

b.

c. e.

capsaicin

(spicy component of hot peppers)

Interpretation Introduction

(a)

Interpretation: The major IR absorptions in the functional group region for the given compound are to be predicted.

Concept introduction: IR spectroscopy is used to identify the functional group present in a compound. Each and every bond vibrates at a characteristic frequency.

Answer to Problem 13.18P

The major IR absorption peaks are observed for ${\text{C}}_{s{p}^3}-{\text{C}}_{s{p}^3}$ bond at ${\text{1500 cm}}^{-1}$ and ${\text{C}}_{s{p}^3}-\text{H}$ bond at $\text{3000}-{\text{2850 cm}}^{-1}$ respectively.

Explanation of Solution

The given compound is octane. It contains ${\text{C}}_{s{p}^3}-\text{H}$ and ${\text{C}}_{s{p}^3}-{\text{C}}_{s{p}^3}$ bonds. Hence, the major IR absorption peaks are observed for ${\text{C}}_{s{p}^3}-{\text{C}}_{s{p}^3}$ bond at ${\text{1500 cm}}^{-1}$ and ${\text{C}}_{s{p}^3}-\text{H}$ bond at $\text{3000}-{\text{2850 cm}}^{-1}$ respectively.

Conclusion

The major IR absorption peaks are observed for ${\text{C}}_{s{p}^3}-{\text{C}}_{s{p}^3}$ bond at ${\text{1500 cm}}^{-1}$ and ${\text{C}}_{s{p}^3}-\text{H}$ bond at $\text{3000}-{\text{2850 cm}}^{-1}$ respectively.

Interpretation Introduction

(b)

Interpretation: The major IR absorptions in the functional group region for the given compound are to be predicted.

Concept introduction: IR spectroscopy is used to identify the functional group present in a compound. Each and every bond vibrates at a characteristic frequency.

Answer to Problem 13.18P

The major IR absorptions are observed for ${\text{C}}_{s{p}^3}-\text{H}$ bond at $\text{3000}-{\text{2850 cm}}^{-1}$, ${\text{C}}_{s{p}^3}-{\text{C}}_{s{p}^3}$ bond at ${\text{1500 cm}}^{-1}$, $\text{O}-\text{H}$ at $\text{3600}-320{\text{0 cm}}^{-1}$ and $\text{C}-\text{O}$ bond at $\text{1150}-1{\text{050 cm}}^{-1}$ respectively.

Explanation of Solution

The given compound is cyclohexanol. It contains ${\text{C}}_{s{p}^3}-\text{H}$, ${\text{C}}_{s{p}^3}-{\text{C}}_{s{p}^3}$, $\text{O}-\text{H}$ and $\text{C}-\text{O}$ bond. Hence, the major IR absorptions are observed for ${\text{C}}_{s{p}^3}-\text{H}$ bond at $\text{3000}-{\text{2850 cm}}^{-1}$, ${\text{C}}_{s{p}^3}-{\text{C}}_{s{p}^3}$ bond at ${\text{1500 cm}}^{-1}$, $\text{O}-\text{H}$ at $\text{3600}-320{\text{0 cm}}^{-1}$ and $\text{C}-\text{O}$ bond at $\text{1150}-1{\text{050 cm}}^{-1}$ respectively.

Conclusion

The major IR absorptions are observed for ${\text{C}}_{s{p}^3}-\text{H}$ bond at $\text{3000}-{\text{2850 cm}}^{-1}$, ${\text{C}}_{s{p}^3}-{\text{C}}_{s{p}^3}$ bond at ${\text{1500 cm}}^{-1}$, $\text{O}-\text{H}$ at $\text{3600}-320{\text{0 cm}}^{-1}$ and $\text{C}-\text{O}$ bond at $\text{1150}-1{\text{050 cm}}^{-1}$ respectively.

Interpretation Introduction

(c)

Interpretation: The major IR absorptions in the functional group region for the given compound are to be predicted.

Concept introduction: IR spectroscopy is used to identify the functional group present in a compound. Each and every bond vibrates at a characteristic frequency.

Answer to Problem 13.18P

The major IR absorptions are observed for ${\text{C}}_{s{p}^3}-\text{H}$ bond at $\text{3000}-{\text{2850 cm}}^{-1}$, ${\text{C}}_{s{p}^2}={\text{C}}_{s{p}^2}$ at ${\text{1650 cm}}^{-1}$, ${\text{C}}_{s{p}^2}-\text{H}$ bond at $\text{3150}-{\text{3000 cm}}^{-1}$${\text{C}}_{s{p}^3}-{\text{C}}_{s{p}^3}$ bond at ${\text{1500 cm}}^{-1}$ respectively.

Explanation of Solution

The given compound is hept-3-ene. It contains ${\text{C}}_{s{p}^3}-\text{H}$, ${\text{C}}_{s{p}^2}={\text{C}}_{s{p}^2}$, ${\text{C}}_{s{p}^2}-\text{H}$ and ${\text{C}}_{s{p}^3}-{\text{C}}_{s{p}^3}$ bonds. Hence, the major IR absorptions are observed for ${\text{C}}_{s{p}^3}-\text{H}$ bond at $\text{3000}-{\text{2850 cm}}^{-1}$, ${\text{C}}_{s{p}^2}={\text{C}}_{s{p}^2}$ bond at ${\text{1650 cm}}^{-1}$, ${\text{C}}_{s{p}^2}-\text{H}$ bond at $\text{3150}-{\text{3000 cm}}^{-1}$${\text{C}}_{s{p}^3}-{\text{C}}_{s{p}^3}$ bond at ${\text{1500 cm}}^{-1}$ respectively.

Conclusion

The major IR absorptions are observed for ${\text{C}}_{s{p}^3}-\text{H}$ bond at $\text{3000}-{\text{2850 cm}}^{-1}$, ${\text{C}}_{s{p}^2}={\text{C}}_{s{p}^2}$ at ${\text{1650 cm}}^{-1}$, ${\text{C}}_{s{p}^2}-\text{H}$ bond at $\text{3150}-{\text{3000 cm}}^{-1}$${\text{C}}_{s{p}^3}-{\text{C}}_{s{p}^3}$ bond at ${\text{1500 cm}}^{-1}$ respectively.

Interpretation Introduction

(d)

Interpretation: The major IR absorptions in the functional group region for the given compound are to be predicted.

Concept introduction: IR spectroscopy is used to identify the functional group present in a compound. Each and every bond vibrates at a characteristic frequency.

Answer to Problem 13.18P

The major IR absorptions are observed for ${\text{C}}_{s{p}^3}-\text{H}$ bond at $\text{3000}-{\text{2850 cm}}^{-1}$, ${\text{C}}_{s{p}^3}-{\text{C}}_{s{p}^3}$ bond at ${\text{1500 cm}}^{-1}$ and ${\text{C}}_{s{p}^2}=\text{O}$ bond at ${\text{1700 cm}}^{-1}$ respectively.

Explanation of Solution

The given compound is cyclohexanone. It contains ${\text{C}}_{s{p}^3}-\text{H}$, ${\text{C}}_{s{p}^3}-{\text{C}}_{s{p}^3}$ and ${\text{C}}_{s{p}^2}=\text{O}$ bonds. Hence, the major IR absorptions are observed for ${\text{C}}_{s{p}^3}-\text{H}$ bond at $\text{3000}-{\text{2850 cm}}^{-1}$, ${\text{C}}_{s{p}^3}-{\text{C}}_{s{p}^3}$ bond at ${\text{1500 cm}}^{-1}$ and ${\text{C}}_{s{p}^2}=\text{O}$ bond at ${\text{1700 cm}}^{-1}$ respectively.

Conclusion

The major IR absorptions are observed for ${\text{C}}_{s{p}^3}-\text{H}$ bond at $\text{3000}-{\text{2850 cm}}^{-1}$, ${\text{C}}_{s{p}^3}-{\text{C}}_{s{p}^3}$ bond at ${\text{1500 cm}}^{-1}$ and ${\text{C}}_{s{p}^2}=\text{O}$ bond at ${\text{1700 cm}}^{-1}$ respectively.

Interpretation Introduction

(e)

Interpretation: The major IR absorptions in the functional group region for the given compound are to be predicted.

Concept introduction: IR spectroscopy is used to identify the functional group present in a compound. Each and every bond vibrates at a characteristic frequency

Answer to Problem 13.18P

The major IR absorptions are observed for ${\text{C}}_{s{p}^2}=\text{O}$ bond at ${\text{1700 cm}}^{-1}$, ${\text{C}}_{s{p}^3}-\text{O}$ bond at $\text{1150}-1{\text{050 cm}}^{-1}$, ${\text{C}}_{s{p}^3}-\text{H}$ bond at $\text{3000}-{\text{2850 cm}}^{-1}$, ${\text{C}}_{s{p}^3}-\text{H}$ bond at $\text{3000}-{\text{2850 cm}}^{-1}$, $\text{O}-\text{H}$ at $\text{3600}-320{\text{0 cm}}^{-1}$, ${\text{C}}_{s{p}^2}={\text{C}}_{s{p}^2}$ at ${\text{1650 cm}}^{-1}$, ${\text{C}}_{s{p}^2}={\text{C}}_{s{p}^2}$ (aromatic) at ${\text{1600 , 1500 cm}}^{-1}$ and $\text{N}-\text{H}$ at $\text{3500}-320{\text{0 cm}}^{-1}$ respectively.

Explanation of Solution

The given compound is capsaicin as shown below.

Figure 1

It contains ${\text{C}}_{s{p}^2}=\text{O}$, ${\text{C}}_{s{p}^3}-\text{O}$, ${\text{C}}_{s{p}^3}-\text{H}$, ${\text{C}}_{s{p}^2}-\text{H}$, $\text{O}-\text{H}$, ${\text{C}}_{s{p}^2}={\text{C}}_{s{p}^2}$, ${\text{C}}_{s{p}^2}={\text{C}}_{s{p}^2}$ (aromatic) and $\text{N}-\text{H}$ bond. Hence, the major IR absorptions are observed for ${\text{C}}_{s{p}^2}=\text{O}$ bond at ${\text{1700 cm}}^{-1}$, ${\text{C}}_{s{p}^3}-\text{O}$ bond at $\text{1150}-1{\text{050 cm}}^{-1}$, ${\text{C}}_{s{p}^3}-\text{H}$ bond at $\text{3000}-{\text{2850 cm}}^{-1}$, ${\text{C}}_{s{p}^3}-\text{H}$ bond at $\text{3000}-{\text{2850 cm}}^{-1}$, $\text{O}-\text{H}$ at $\text{3600}-320{\text{0 cm}}^{-1}$, ${\text{C}}_{s{p}^2}={\text{C}}_{s{p}^2}$ bond at ${\text{1650 cm}}^{-1}$, ${\text{C}}_{s{p}^2}={\text{C}}_{s{p}^2}$ (aromatic) bond at ${\text{1600 cm}}^{-1}$ and $\text{N}-\text{H}$ bond at $\text{3500}-320{\text{0 cm}}^{-1}$ respectively.

Conclusion

The major IR absorptions are observed for ${\text{C}}_{s{p}^2}=\text{O}$ bond at ${\text{1700 cm}}^{-1}$, ${\text{C}}_{s{p}^3}-\text{O}$ bond at $\text{1150}-1{\text{050 cm}}^{-1}$, ${\text{C}}_{s{p}^3}-\text{H}$ bond at $\text{3000}-{\text{2850 cm}}^{-1}$, ${\text{C}}_{s{p}^3}-\text{H}$ bond at $\text{3000}-{\text{2850 cm}}^{-1}$, $\text{O}-\text{H}$ at $\text{3600}-320{\text{0 cm}}^{-1}$, ${\text{C}}_{s{p}^2}={\text{C}}_{s{p}^2}$ at ${\text{1650 cm}}^{-1}$, ${\text{C}}_{s{p}^2}={\text{C}}_{s{p}^2}$ (aromatic) at ${\text{1600 , 1500 cm}}^{-1}$ and $\text{N}-\text{H}$ at $\text{3500}-320{\text{0 cm}}^{-1}$ respectively.