Infrared IR spectroscopy is a powerful analytical technique used to identify functional groups in organic molecules by analyzing the molecular vibrations that occur when the molecule absorbs infrared radiation. Each functional group has a characteristic absorption frequency, which corresponds to the energy required to excite the molecular vibrations associated with that group.To identify the functional groups present in a given organic molecule using IR spectroscopy, follow these steps:1. Obtain the IR spectrum of the molecule: The IR spectrum is a plot of the absorbance or transmittance of the molecule as a function of the frequency or wavenumber of the infrared radiation. The spectrum will display peaks at the frequencies where the molecule absorbs the radiation.2. Examine the fingerprint region 600-1500 cm : This region contains many peaks that are specific to the individual molecule and can be used to confirm the identity of the molecule. However, it is not particularly useful for identifying functional groups.3. Identify the functional groups by analyzing the peaks in the functional group region 1500-4000 cm : This region contains peaks that correspond to the characteristic absorption frequencies of various functional groups. Some common functional groups and their corresponding IR absorption frequencies are: - Hydroxyl group OH : Broad peak around 3200-3600 cm - Carboxylic acid COOH : Broad peak around 2500-3300 cm OH and sharp peak around 1700-1720 cm C=O - Amine NH or NH : Broad peak around 3100-3500 cm - Alkene C=C : Sharp peak around 1620-1680 cm - Carbonyl C=O : Sharp peak around 1650-1750 cm - Nitrile CN : Sharp peak around 2210-2260 cm - Alkyne CC : Sharp peak around 2100-2250 cm often weak or absent 4. Analyze the molecular vibrations: The peaks in the IR spectrum correspond to the molecular vibrations associated with the functional groups present in the molecule. These vibrations can be classified into four types: - Stretching vibrations: These involve a change in the bond length, such as the symmetric and asymmetric stretching of C-H, C-O, or C-N bonds. - Bending vibrations: These involve a change in the bond angle, such as the scissoring, rocking, wagging, or twisting of C-H, C-O, or C-N bonds. - In-plane vibrations: These occur in the plane of the molecule and include stretching and bending vibrations. - Out-of-plane vibrations: These occur perpendicular to the plane of the molecule and include bending vibrations.By analyzing the molecular vibrations observed in the IR spectrum, you can determine the functional groups present in the molecule and gain insight into the molecule's structure.