IR spectroscopy guide to identifying common functional groups
1. The scale UNITS: cm-1 unit is the wavenumber and is given by 1 / (wavelength in cm). ṽ = 1/ λ Infrared (IR) spectroscopy deals spectrum with the interaction between a molecule and radiation from the IR region of the electromagnetic (IR region = 4000 - 400 cm-1).
2. IR radiation causes the excitation of the vibrations of covalent bonds within that molecule ( motions between nuclei). These vibrations include the stretching and bending modes
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6. The IR Chart 1800-1600 C=O C=N C=N ~3300 H-EN ~2300 C Ξ C C Ξ N
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8. Single bonds: n-hexane Alkanes C-H 2960-2850 (strong, stretching), 1470-1350 (bending) U S
11. Methyl benzene Aromatic Rings C=C 1600-1500 (stretching) =C-H 3100-3000 (stretching), 2000-1600 (phenyl ring substitution overtones) U S overtones Double bonds /hydrocarbons
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13. Acetone: Residues of acetone used during cleaning or in contamination during GC analysis will be observed with a weak peak at 1715 cm-1 Other double bonds
14. 1-HEXYNE Triple bonds /hydrocarbons Alkynes C-H 3333-3267(sharp, strong, stretching), 700-610 (bending) C Ξ C 2260-2100 (sharp, medium, stretching) Ξ C-H C Ξ C
