Final answer:
Terminal alkynes have an IR spectrum with a C≡C stretching absorption peak between 2100-2250 cm⁻¹, and a terminal hydrogen C-H bond stretch near 3300 cm⁻¹. These peaks are less intense than those of more polar bonds, such as carbonyls, due to the lower polarity of the C≡C bond.
Step-by-step explanation:
To describe the IR spec for terminal alkyne peaks, we focus on two distinct regions of the infrared (IR) spectrum where alkynes show characteristic absorbance due to vibrational transitions. Terminal alkynes exhibit a notable absorption peak for the carbon-carbon triple bond (C≧C) stretching vibration, typically observed in the range of 2100-2250 cm⁻¹ due to their less polar nature. Additionally, the terminal hydrogen connected to the sp-hybridized carbon in terminal alkynes imparts an absorption band at around 3300 cm⁻¹, which is attributable to the stretching of the C-H bond.
Unlike the strong absorption of more polar bonds such as the carbonyl group in ketones, alkyne absorptions tend to be weaker. However, IR spectroscopy is an invaluable tool as it provides characteristic peaks, allowing for the identification of specific functional groups within a molecule. This technique is particularly helpful when used in conjunction with other methods to confirm the presence of terminal alkynes within a compound.