This chapter will focus on infrared (IR) spectroscopy. The wavelengths found in infrared radiation are a little longer than those found in visible light. IR spectroscopy is useful for finding out what kinds of bonds are present in a molecule, and knowing what kinds of bonds are present is a good start towards knowing what the structure could be.
- 3.2: Hydrocarbon Spectra
- All organic and biological compounds contain carbon and hydrogen, usually with various other elements as well. Hydrocarbons are compounds containing only carbon and hydrogen, but no other types of atoms. Since all organic compounds contain carbon and hydrogen, looking at hydrocarbon spectra will tell us what peaks are due to the basic C&H part of these molecules.
- 3.3: Some Subtle Points of IR Spectroscopy
- Alkanes show two sets of peaks in the IR spectrum. Alkanes contain two kinds of bonds: C-C bonds and C-H bonds. However, these two facts are not related. The reasons are explained through bond polarity and molecular vibrations.
- 3.7: Bonds to Common Heteroatoms- Nitrogen
- The IR spectra of nitrogen-containing compounds can be messier than the ones you have seen so far. N-H bends and C-N stretches tend to be broader and weaker than peaks involving oxygen atoms. However, some peaks in nitrogen compounds are useful. The problems in this section will guide you through some of these features.