Final answer:
IR spectra of alkynes display peaks at 2100-2250 cm⁻¹ due to the carbon-carbon triple bond and an additional peak around 3300 cm⁻¹ for terminal alkynes, which is associated with the CH bond involving sp-hybridized carbon.
Step-by-step explanation:
The infrared (IR) spectroscopy of molecules containing CH bonds with sp hybridization, typically found in alkynes, exhibits characteristic absorbance peaks. For an alkyne, the carbon-carbon triple bond results in an IR absorbance peak in the range of 2100-2250 cm⁻¹. Additionally, if the alkyne is terminal, meaning it has a hydrogen atom bonded to the end carbon of the triple bond, this CH bond results in an IR absorbance at approximately 3300 cm⁻¹. This bond involves a carbon that is sp-hybridized, forming a linear geometry with the attached hydrogen, and due to its reduced symmetry compared to other types of hydrocarbons, the CH stretching in these molecules is IR active and thus detectable in their spectra.