IR Absorption Peaks and Intensities of Functional Groups - UCSC IR Tables, Lecture notes of Organic Chemistry

Download IR Absorption Peaks and Intensities of Functional Groups - UCSC IR Tables and more Lecture notes Organic Chemistry in PDF only on Docsity! IR Tables, UCSC Table 1. Characteristic IR Absorption Peaks of Functional Groups* Vibration Position (cm-1) Intensity* Notes Alkanes C-H stretch 2990 – 2850 m to s Alkenes =C-H stretch 3100 – 3000 m C=C stretch 1680 – 1620 (sat.) 1650 – 1600 (conj.) w to m =C-H bend 995 – 685 s See Table 2 for detail Alkynes ≡C-H stretch 3310 – 3200 s C≡C stretch 2250 – 2100 m to w Aromatic Compounds C-H stretch 3100 – 3000 m to w C=C stretch 1625 – 1440 m to w Hidden in fingerprint region C-H bend 900 – 680 s See Table 2 for detail Alcohols** O-H stretch 3550 – 3200 br, s Hydrogen bonded (typical) Amines N-H stretch 3550 – 3250 br, m Primary (two bands) Secondary (one band) Nitriles C≡N stretch 2280 – 2200 s Aldehydes C-H stretch 2900 – 2800 & 2800 – 2700 s H-C=O Fermi doublet C=O stretch 1740 – 1720 (sat.) 1715 – 1680 (conj.) s Ketones C=O stretch 1750 – 1705 (sat.) 1700 – 1665 (conj.) s Esters** C=O stretch 1765 – 1735 (sat.) 1730 – 1715 (conj.) s Carboxylic Acids** O-H stretch 3200 – 2500 br, m to w C=O stretch 1725 – 1700 (sat.) 1715 – 1680 (conj.) s Amides N-H stretch 3500 – 3150 m Primary (two bands) Secondary (one band) C=O stretch 1700 – 1630 s IR Tables, UCSC Table 1 cont’d Vibration Position (cm-1) Intensity Notes Anhydrides** C=O stretch 1850 – 1800 & 1790 – 1740 s Acid Chlorides C=O stretch 1815 – 1770 s Nitro Compounds NO2 stretch 1570 – 1490 & 1390 – 1300 s Thiols† R-S-H stretch 2550 – 2600 Alkyl & Aryl Halides† C-F stretch 1000 – 1400 Hidden in fingerprint region C-Cl stretch < 600 – 840 C-Br stretch < 700 C-I stretch < 600 * Abbreviations: s = strong; m = medium; w = weak; br = broad; sat. = saturated; conj. = conjugated ** Alcohols, Esters, Carboxylic Acids, and Anhydrides also absorb in the fingerprint region due to the C-O stretch (1300 – 1000, s). Table 2. Out-of-Plane C-H Bending Vibrations in Alkenes and Aromatics Alkene Structure Position (cm-1) Phenyl Structure Position (cm-1) Mono-substituted 997 – 985 & 915 – 905 Mono-substituted 770 – 730 & 720 – 680 Disubstituted, trans 980 – 960 Disubstituted, ortho 770 – 735 Disubstituted, cis 730 – 665 Disubstituted, meta 810 – 750 & 725 – 680 Disubstituted, symm. 895 – 885 Disubstituted, para 860 – 800 Trisubstituted 840 – 790 * Adapted from…Mohrig, J. R.; Hammond, C. N.; Schatz, P. F. “Infrared Spectroscopy” in Techniques in Organic Chemistry. Freeman: New York, 2006. † Palleros, D. R. “Infrared Spectroscopy” in Experimental Organic Chemistry. Wiley: New York, 2000. p. 688. R H H H R R H R H R R R H H R RR R R H H R R R R H R CHEM 108M, Nuclear Magnetic Resonance (NMR) UCSC, Binder Figures from Mohrig’s Techniques in Organic Chemistry, 3rd Edition. 5 CHEM 108M, Nuclear Magnetic Resonance (NMR) UCSC, Binder Figures from Mohrig’s Techniques in Organic Chemistry, 3rd Edition. 6