Chapter 26, Problem 26.78P

Interpretation Introduction

Interpretation:

It is to be explained how IR spectroscopy could be used to monitor the conversion of $\text{poly}\left(\text{vinyl acetate}\right)$ to $\text{poly}\left(\text{vinyl alcohol}\right)$, that is, how can a chemist use IR to tell if $\text{poly}\left(\text{vinyl acetate}\right)$ has been converted to $\text{> 99\%}$$\text{poly}\left(\text{vinyl alcohol}\right)$.

Concept introduction:

The IR spectroscopy is limited for knowing the functional group in the compound. The peaks in the IR spectroscopy are also called IR bands. Some characteristics band of important functional groups are given below.

The alcoholic and acidic $\text{OH}$ groups give a broad band above ${\text{3000 cm}}^{\text{-1}}$ due to H bonding. Carbonyl group gives strong absorption in a range from ${\text{1850 – 1630 cm}}^{\text{-1}}$. Especially carbonyl group of an ester gives strong absorption in a range of ${\text{1735 – 1750 cm}}^{\text{-1}}$; the carbonyl group of an aldehyde gives absorption band at ${\text{1720 -1740 cm}}^{\text{-1}}$.

So IR spectroscopy is an important tool for the identification of functional groups; thereby it is also used to know how much a reaction proceeds by comparing IR spectra of the product with its starting.