IR Absorption Frequencies of Functional Groups Containing a Carbonyl (C=O) Functional Characteristic Absorptions Type of Vibration Intensity Group (cm-1) Carbonyl C=O stretch 1670-1820 strong (conjugation moves absorptions to lower wave numbers) Acid C=O stretch 1700-1725 strong O-H stretch 2500-3300 strong, very broad C-O stretch 1210-1320 strong Aldehyde C=O stretch 1740-1720 strong =C-H stretch 2820-2850 & 2720-2750 medium, two peaks Amide C=O stretch 1640-1690 strong N-H stretch 3100-3500 unsubstituted have two bands N-H bending 1550-1640 Anhydride C=O stretch 1800-1830 & 1740-1775 two bands Ester C=O stretch 1735-1750 strong C-O stretch 1000-1300 two bands or more Ketone acyclic stretch 1705-1725 strong 3-membered - 1850 4-membered - 1780 cyclic stretch 5-membered - 1745 strong 6-membered - 1715 7-membered - 1705 stretch 1665-1685 strong ,-unsaturated aryl ketone stretch 1680-1700 strong Data from http://www2.ups.edu/faculty/hanson/Spectroscopy/IR/IRfrequencies.html Fields of Advanced Difficulty Theoretical
IR Absorption Frequencies of Functional Groups Containing a Carbonyl (C=O) Functional Group Type of Vibration Characteristic Absorptions (cm-1) Intensity Carbonyl C=O stretch 1670-1820 strong (conjugation moves absorptions to lower wave numbers) Acid C=O stretch 1700-1725 strong O-H stretch 2500-3300 strong, very broad C-O stretch 1210-1320 strong Aldehyde C=O stretch 1740-1720 strong =C-H stretch 2820-2850 & 2720-2750 medium, two peaks Amide C=O stretch 1640-1690 strong N-H stretch 3100-3500 unsubstituted have two bands N-H bending 1550-1640 Anhydride C=O stretch 1800-1830 & 1740-1775 two bands Ester C=O stretch 1735-1750 strong C-O stretch 1000-1300 two bands or more Ketone acyclic stretch 1705-1725 strong cyclic stretch 3-membered - 1850 4-membered - 1780 5-membered - 1745 6-membered - 1715 7-membered - 1705 strong ,-unsaturated stretch 1665-1685 strong aryl ketone stretch 1680-1700 strong Data from http://www2.ups.edu/faculty/hanson/Spectroscopy/IR/IRfrequencies.html Fields of Advanced Difficulty Theoretical
49th_IChO_PreparatoryProblem.docx