Infrared (IR) spectroscopy is commonly used to study the molecular vibrations of compounds. The different absorption regions you mentioned correspond to different types of molecular vibrations, which can provide information about the functional groups present in a compound.
The region from 1500-4000 cm^-1 is known as the "fingerprint region" because it contains a complex and unique pattern of absorption bands for each compound. It is often used to identify compounds or to compare spectra for different samples.
The region from 4000-2500 cm^-1 is referred to as the "mid-IR region" or "functional group region." It contains characteristic absorption bands associated with functional groups such as carbonyl (C=O), hydroxyl (OH), and amino (NH) groups. Analyzing this region can help identify specific functional groups present in a compound.
The region from 600-1500 cm^-1 is called the "fingerprint region" as well, and it can also provide information about the presence of specific functional groups or structural features. This region often includes absorption bands related to bending vibrations of organic compounds.
To determine which absorption region would show different peaks for two different compounds, we need more specific information about the compounds or their functional groups. Different compounds have different characteristic absorption bands, and the specific regions of interest can vary depending on the compounds involved.