Consider the following statements as they apply to infrared spectroscopy. Decide if each is true or false. a. Absorption bands in infrared spectroscopy are due to vibrational and rotational-vibrational transitions in molecules. b. Because molecules in condensed phases (solids and liquid) are not free to rotate, rotational-vibrational transitions are not observed in their infrared spectra.
c. For this reason, even at high resolution, a condensed phase spectrum is characterized by broad bands.
d. For a given pair of atoms, the vibrational frequency expected if they are joined by a single bond should be higher than if they are joined by a double bond.
e. For a vibrational mode to be infrared active, the vibration must cause a change in the polarizability of the molecule. Air contains nitrogen and oxygen - both of which strongly absorb infrared radiation.
f. For this reason, most FTIR instrument are operated under vacuum.