Chapter 15, Problem 15.21P

Interpretation Introduction

Interpretation:

The given isomer, A or B, that are consistent with IR spectra provided is to be determined. The reason for it is to be explained.

Concept introduction:

OH stretch bands are intense and are usually rather broad, centered above 3000 ${\text{cm}}^{-1}$. The broadening of an OH stretch band is due to hydrogen bonding involving OH groups of the sample. A network of hydrogen bonding in a sample facilitates a rapid exchange of hydrogen atoms from one OH group to another as each OH hydrogen atom is already partially bonded to two different oxygen atoms. This process gives rise to a lot of variation in the $\text{O-H}$ bond strengths. An alcohol $\text{O-H}$ stretch is typically centered near 3300 ${\text{cm}}^{-1}$ and is usually well resolved from the alkane $\text{C-H}$ stretch bands between 2800 and 3000 ${\text{cm}}^{-1}$. A carboxylic acid $\text{O-H}$ stretch is centered at around 3000 ${\text{cm}}^{-1}$ and can extend down to 2500 ${\text{cm}}^{-1}$, thus overlapping the alkane $\text{C-H}$ stretches.