Final answer:
The O-H stretch in alcohols appears around 3400 cm⁻¹ as a broad peak in the infrared spectrum, indicating the presence of an alcohol group and is due to intermolecular hydrogen bonding.
Step-by-step explanation:
The O-H stretch in alcohols is observed in infrared (IR) spectroscopy as a distinct peak due to the vibration of the oxygen-hydrogen bond. This O-H stretching vibration typically appears as a very broad signal centered around 3400 cm⁻¹ in the IR spectrum.
The broadness of this peak is due to the hydrogen bonding that occurs between alcohol molecules, similar to the H-O-H bond in water, making alcohols polar. The IR spectrum of alcohols exhibits a characteristic hydrogen bonding pattern that increases thermal energy required to break the intermolecular forces as compared to alkanes.
Also, the presence of the OH group in alcohols allows them to participate in hydrogen bonding, making the physical and chemical properties of alcohols different from those of alkanes.