2021-11-11
Fourier Transform Infrared Spectroscopy (FT-IR): Adipic Acid
Fourier Transform Infrared (FTIR) spectrum is used to identify functional groups in a sample by measuring the absorption of infrared light at different wavenumbers (cm⁻¹).
The assignment of specific absorption peaks to functional groups in an FTIR spectrum is based on established empirical data. Different bonds absorb infrared radiation at characteristic wavenumbers due to the bond vibrations (stretching or bending) being influenced by bond strength, atomic masses, and the surrounding chemical environment.
1. O-H Stretching (~3455 cm⁻¹)
Hydroxyl groups (-OH) typically absorb in the region 3200-3600 cm⁻¹. In this spectrum, the broad peak around 3455.90 cm⁻¹ falls within this range, which suggests an O-H stretching vibration.
2. C-H Stretching (~2858 cm⁻¹):
A sharp peak at 2858.40 cm⁻¹ likely corresponds to the C-H stretching vibrations, indicating the presence of aliphatic hydrocarbons (C-H bonds in -CH₂ or -CH₃ groups).
3. C=O Stretching (~1742 cm⁻¹)
Carbonyl (C=O) groups have a characteristic strong absorption in the range 1650-1750 cm⁻¹, depending on whether the compound is an aldehyde, ketone, ester, or carboxylic acid. The strong peak at 1742.63 cm⁻¹ is consistent with the C=O stretching mode, indicating a carbonyl group. This specific frequency suggests it could be part of a carboxylic acid or ester.
Based on the strong O-H and C=O stretching bands, this sample likely contains a carboxylic acid functional group (-COOH).
The presence of aliphatic C-H stretching and bending vibrations suggests that the sample contains alkyl groups (-CH₂ or -CH₃).
The peaks in the fingerprint region (below 1500 cm⁻¹) confirm the presence of additional C-O or C-H bonds, likely from complex hydrocarbons or ester functionalities.
The spectrum might represent adipic acid <(CH2)4(COOH)2 > or a related organic compound, which contains both carboxyl (-COOH) and alkyl (-CH₂) groups.
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