Final answer:
In IR spectroscopy, the two types of stretching vibration modes are symmetric and asymmetric. Symmetric stretching involves atoms moving in unison, while asymmetric stretching involves atoms moving in opposite directions, changing the dipole moment. Such vibrations enable the identification and analysis of molecular structures.
Step-by-step explanation:
The two types of stretching vibration modes in IR spectroscopy are a) Symmetric and asymmetric. The energy of molecular vibration is quantized, with molecules absorbing energy at specific frequencies corresponding to their vibrational modes. In terms of bonding, covalent bonds are likened to springs at the molecular level, with each bond having characteristic frequencies at which they "bounce" or vibrate. These vibrations include both the symmetric and asymmetric stretching modes. Symmetric stretching occurs when the atoms on either side of a bond move in unison, either towards or away from each other, while asymmetric stretching happens when one atom moves toward the center of mass while the other moves away, causing a change in dipole moment. Infrared spectra can thus be used to distinguish among different organic compounds, such as isomers, by observing the differing absorption bands of their specific vibrational modes.
Some kinds of vibrations, such as the stretching of completely symmetrical double and triple bonds, may be infrared inactive because they do not result in a change in dipole moment. However, other bonds and vibrational modes in these molecules do absorb IR light, providing useful information about molecular structure. Furthermore, the IR spectroscopy can be used to detect and analyze the various stretching and bending modes of carbon-carbon and carbon-hydrogen bonds, aiding in the identification of different organic compounds, as evidenced by laboratory techniques and interstellar observations.