Chapter 15, Problem 15.17YT

Interpretation Introduction

Interpretation:

In each of the given spectra, the band corresponding to a triple-bond stretching mode is to be identified.

Concept introduction:

Triple bonds are generally among the easiest to identify in an IR spectrum, because no other absorption bands appear where they do. Triple-bond stretching modes appear between $\text{2000}$ and ${\text{2500 cm}}^{\text{-1}}$. The $\text{C}\equiv \text{C}$ and $\text{C}\equiv \text{N}$ bonds both appear as sharp bands at roughly the same position with $\text{C}\equiv \text{C}$ between $\text{21}00$ and ${\text{2260 cm}}^{\text{-1}}$ and $\text{C}\equiv \text{N}$ between $\text{221}0$ and ${\text{2260 cm}}^{\text{-1}}$. $\text{RC}\equiv \text{CR}$ stretches typically have weak absorption intensities, $\text{RC}\equiv \text{N}$ absorptions have moderate intensities.