Final answer:
The IR absorption ranges for N-H, O-H, and C-H vary, typically with N-H and broad O-H absorptions between 3200-3550 cm¹, and sp³ C-H absorptions between 2850-3300 cm¹. Infrared spectroscopy identifies functional groups through distinct absorption frequencies, where the dipole moment changes during molecular vibrations.
Step-by-step explanation:
The IR absorption range for single bonds such as N-H, O-H, and C-H varies according to the type of vibration and the specific atoms involved. Typically, the N-H bond shows absorption between 3300-3500 cm¹ due to stretching vibrations. The O-H bond, often seen in alcohols, also absorbs in a similar range but can shift depending on hydrogen bonding and appears as a broad peak around 3200-3550 cm¹. The C-H bond absorption depends on the type of carbon it is attached to (sp³, sp², or sp hybridized), with sp³ C-H stretching vibrations usually occurring between 2850-3300 cm¹.
Infrared spectroscopy is very effective for identifying functional groups in organic compounds due to distinctive absorbance frequencies. For example, a ketone group's carbonyl bond would absorb in the range of 1650-1750 cm¹, which is distinct from the broader range of carbon-carbon triple bonds found in alkynes, which show weaker absorption due to their lower polarity.
The mentioned compounds in the Spectral Database for Organic Compounds can be analyzed to identify their characteristic absorption bands and understand molecular vibrations, reflecting the periodic change in dipole moment, which allows infrared active vibrations to be detected in IR spectroscopy. This underlies the fundamental concept that different bonds will absorb different wavelengths due to the variation in mass and bond strength, following the analogy of bonds acting as springs.