Final answer:
Nitriles exhibit a distinct peak in the IR spectrum in the range of 2200-2260 cm¹ due to the stretching of the carbon-nitrogen triple bond (C≡N). This peak is sharp and prominent, making it a reliable indicator of the presence of a nitrile group in a molecule.
Step-by-step explanation:
Nitriles, also known as cyanides, exhibit distinct peaks in the infrared (IR) spectrum that can be used to identify their presence. The characteristic peak for nitriles appears in the range of 2200-2260 cm¹ and is attributed to the stretching of the carbon-nitrogen triple bond (C≡N). This peak is typically sharp and prominent, making it a reliable indicator of the presence of a nitrile group in a molecule. For example, if we have a compound like propionitrile (CH₃CH₂CN), we would expect to see a strong peak at around 2240 cm¹ in its IR spectrum. This peak is caused by the stretching vibration of the carbon-nitrogen triple bond in propionitrile. It's worth noting that there may be other peaks present in the IR spectrum that correspond to other functional groups or molecular vibrations. However, the distinctive peak in the 2200-2260 cm¹ range is the key feature to look for when identifying nitriles.