Chapter 16, Problem 16.38P

Interpretation Introduction

Interpretation:

The structure of the given unknown compound is to be proposed from the given information.

Concept introduction:

The IR spectroscopy is limited to know which functional group is present in the compound. The peaks in the IR spectroscopy are also called IR bands. Some characteristic bands 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 ${\text{1735 – 1750 cm}}^{\text{-1}}$, and that of an amide group is ${\text{1630 - 1690 cm}}^{\text{-1}}$. The carbonyl group of an aldehyde gives absorption band at ${\text{1720 -1740 cm}}^{\text{-1}}$. ${}^{13}\text{C}$ NMR provides valuable information about the carbon skeleton. Each signal in the ${}^{13}\text{C}$ NMR equals the number of distinct carbon atoms in the given unknown compound. The mass spectroscopy is limited to know the exact mass of an unknown compound, but this information is not enough to know the structure of the unknown. Only some important fragment and base peak in mass spectrum suggests the possible structures, but they are not exactly correct.