Infrared_Absorption_Frequencies

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Infrared Absorption Frequencies 
[de: http://chemistry.umeche.maine.edu/CHY251/IR-Table.html] 
 
Numbers separated by dashes are ranges; when two numbers are separated by a comma, both absorptions 
are expected. Individual numbers not components of a range should be considered  5 cm-1. 
Intensity of absorptions (relative height of peak) is keyed by letter: s = strong; m = medium; w = weak; v 
= very; br = broad. 
 
Compound Class Structure , cm-1 Intensity Assignment 
Alkanes RCH2CH3 
2850-3000 
1450-1470 
1370-1380 
720-725 
s 
s 
s 
m 
CH stretch 
CH2 and CH3 
bending modes 
Alkenes RCH=CH2 
3040-3140 
1655 
910, 990 
m 
m 
s 
=C-H stretch 
C=C stretch 
=CH out of plane 
 R2C=CH2 
3080-3140 
1650 
890 
s 
m 
s 
=C-H stretch 
C=C stretch 
=CH out of plane 
 Z- RCH=CHR 
3020 
1660 
675-725 
w 
w 
m 
=C-H stretch 
C=C stretch 
=CH out of plane 
 (a) 3-ring 1641 w C=C stretch 
 (b) 4-ring 1566 w " 
 (c) 5-ring 1611 w " 
 (d) 6-ring 1649 w " 
 (e) 7-ring 1651 w " 
 (f) 8-ring 1653 w " 
 E- RCH=CHR 
3020 
1675 
970 
w 
w 
s 
=C-H stretch 
C=C stretch 
=CH out of plane 
 R2C=CHR 
3020 
1670 
790-840 
w 
w 
s 
=C-H stretch 
C=C stretch 
=CH out of plane 
 R2C=CR2 1670 
vw to 
missing 
C=C stretch 
Alkynes RCCH 
3300 
2100-2140 
600-700 
s 
m 
s 
 CH stretch 
CC stretch 
C-H bend 
 
RC CR 2190-2260 
vw to 
missing 
C C stretch 
Alkyl Halides R-F 1000-1350 s C-F stretch 
 R-Cl 750-850 s C-Cl stretch 
 R-Br 500-680 s C-Br stretch 
 R-I 200-500 out of range C-I stretch 
Alcohols RCH2OH 
3400-3600 
1050 
varies 
s 
OH stretch 
C-O stretch 
 R2CHOH 
3400-3600 
1100 
varies 
s 
OH stretch 
C-O stretch 
 R3COH 3400-3600 s OH stretch 
Ethers R-O-R 1070-1150 s C-O stretch 
Aldehydes RCHO 1725 s C=O stretch 
 C=CCHO 1685 s C=O stretch 
 ArCHO 1700 s C=O stretch 
 All aldehydes 
2720, 2820 
(both) 
m CHO out of plane 
Ketones R2CO 1715 s C=O stretch 
 (a) 4-ring 1780 " " 
 (b) 5-ring 1745 (doublet) " " 
 (c) 6-ring 1715 " " 
 C=CCOR 1675 m " 
 ArCOR 1690 s " 
Carboxylic Acids RCO2H 
3400 
1760 
2800-3400 
1710 
s 
s 
s (broad) 
s 
monomer OH 
monomer C=O 
dimer OH 
dimer C=O 
 C=CCO2H 
3400 
1720 
2800-3400 
1690 
s 
s 
s (broad) 
s 
monomer OH 
monomer C=O 
dimer OH 
dimer C=O 
 RCO2
-
 
1550-1610 
1400 
>m 
" 
C-O stretch 
" 
Esters RCO2R' 1735 s C=O stretch 
 (a) 5-ring 1770 s " 
 (b) 6-ring 1735 s " 
 C=CCO2R 1720 s " 
 ArCO2R 1720 s " 
Amides RCONH2 
3500 
1690 
3400 
1650 
1600-1640 
m 
s 
m 
s 
s 
NH stretch (free) 
C=O stretch (free) 
NH str. (H-bond) 
C=O str. (H-bond) 
NH out of plane 
 RCONHR 
3440 
1680 
3330 
1650 
1530-1550 
m 
s 
m 
s 
m 
NH stretch (free) 
C=O stretch (free) 
NH str. (H-bond) 
C=O str. (H-bond) 
NH out of plane 
 (a) 4-ring 1745 s C=O stretch 
 (b) 5-ring 1700 " " 
 (c) 6-ring 1640 " " 
 RCONR2 1650 m C=O stretch 
Anhydrides RCO2COR 
1760, 1820 
(both) 
s 
C=O stretch; symm., 
unsymm. 
Acid Chloride RCOCl 1800 s C=O stretch 
Amines RNH2 
3400, 3500 
(both) 
1560-1640 
1030-1230 
w 
s 
m 
NH stretch 
NH2 in plane bend 
C-N stretch 
 R2NH 
3310-3350 
1030-1230 
w 
m 
NH stretch 
C-N stretch 
 Ar2NH 
3450 
1250-1360 
w 
s 
NH stretch 
Ar-N stretch 
Benzenes monosubst. 
730-770 
690-710 
m 
m 
CH out of plane bending 
 ortho-disub. 735-770 m " 
 meta-disub. 
750-810 
690-710 
m 
m 
" 
 para-disub. 810-840 m " 
 1,2,3-trisub. 
760-780 
705-745 
m 
m 
" 
 1,3,5-trisub. 
810-865 
675-730 
m 
m 
" 
 1,2,4-trisub. 
805-825 
870-885 
m 
m 
" 
 1,2,3,4-tetrasub. 800-810 m " 
 1,2,4,5-tetrasub. 855-870 m " 
 1,2,3,5-tetrasub. 840-850 m " 
 
1,2,3,4,5-
pentasub. 
870 w " 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
The following table lists infrared spectroscopy absorptions by frequencies. 
[de: http://www.ochemonline.com/Infrared_spectroscopy_absorption_table] 
 
4000-3000 cm
-1
 
3700-3584 medium sharp O-H stretching alcohol free 
3550-3200 strong broad O-H stretching alcohol 
intermolecular 
bonded 
3500 
3400 
medium 
 
N-H stretching primary amine 
 
3400-3300 
3330-3250 
medium 
 
N-H stretching 
aliphatic primary 
amine 
3350-3310 medium 
 
N-H stretching secondary amine 
 
3300-2500 strong broad O-H stretching carboxylic acid 
usually centered on 
3000 cm
-1
 
3200-2700 weak broad O-H stretching alcohol 
intramolecular 
bonded 
3000-2800 strong broad N-H stretching amine salt 
 
3000-2500 cm
-1
 
3333-3267 strong sharp C-H stretching alkyne 
 
3100-3000 medium 
 
C-H stretching alkene 
 
3000-2840 medium 
 
C-H stretching alkane 
 
2830-2695 medium 
 
C-H stretching aldehyde doublet 
2600-2550 weak 
 
S-H stretching thiol 
 
2400-2000 cm
-1
 
2349 strong 
 
O=C=O stretching carbon dioxide 
 
2275-2250 strong broad N=C=O stretching isocyanate 
 
2260-2222 weak 
 
CΞN stretching nitrile 
 
2260-2190 weak 
 
CΞC stretching alkyne disubstituted 
2175-2140 strong 
 
S-CΞN stretching thiocyanate 
 
2160-2120 strong 
 
N=N=N stretching azide 
 
2150 
 
C=C=O stretching ketene 
 
2145-2120 strong 
 
N=C=N stretching carbodiimide 
 
2140-2100 weak 
 
CΞC stretching alkyne monosubstituted 
2140-1990 strong 
 
N=C=S stretching isothiocyanate 
 
2000-1900 medium 
 
C=C=C stretching allene 
 
2000 
 
C=C=N stretching ketenimine 
 
2000-1650 cm
-1
 
2000-1650 weak 
 
C-H bending 
aromatic 
compound 
overtone 
1870-1540 cm
-1
 
1818 
1750 
strong 
 
C=O stretching anhydride 
 
1815-1785 strong 
 
C=O stretching acid halide 
 
1800-1770 strong 
 
C=O stretching 
conjugated acid 
halide 
1775 
1720 
strong 
 
C=O stretching 
conjugated 
anhydride 
1770-1780 strong 
 
C=O stretching vinyl / phenyl ester 
 
1760 strong 
 
C=O stretching carboxylic acid monomer 
1750-1735 strong 
 
C=O stretching esters 6-membered lactone 
1750-1735 strong 
 
C=O stretching δ-lactone γ: 1770 
1745 strong 
 
C=O stretching cyclopentanone 
 
1740-1720 strong 
 
C=O stretching aldehyde 
 
1730-1715 strong 
 
C=O stretching 
α,β-unsaturated 
ester 
or formates 
1725-1705 strong 
 
C=O stretching aliphatic ketone 
or cyclohexanone or 
cyclopentenone 
1720-1706 strong 
 
C=O stretching carboxylic acid dimer 
1710-1680 strong 
 
C=O stretching conjugated acid dimer 
1710-1685 strong 
 
C=O stretching 
conjugated 
aldehyde 
1690 strong 
 
C=O stretching primary amide 
free (associated: 
1650) 
1690-1640 medium 
 
C=N stretching imine / oxime 
 
1685-1666 strong 
 
C=O stretching conjugated ketone 
 
1680 strong 
 
C=O stretching secondary amide 
free (associated: 
1640) 
1680 strong 
 
C=O stretching tertiary amide 
free (associated: 
1630) 
1650 strong 
 
C=O stretching δ-lactam 
γ: 1750-1700 β: 
1760-1730 
1670-1600 cm
-1
 
1678-1668 weak 
 
C=C stretching alkene disubstituted(trans) 
1675-1665 weak 
 
C=C stretching alkene trisubstituted 
1675-1665 weak 
 
C=C stretching alkene tetrasubstituted 
1662-1626 medium 
 
C=C stretching alkene disubstituted (cis) 
1658-1648 medium 
 
C=C stretching alkene vinylidene 
1650-1600 medium 
 
C=C stretching conjugated alkene 
 
1650-1580 medium 
 
N-H bending amine 
 
1650-1566 medium 
 
C=C stretching cyclic alkene 
 
1648-1638 strong 
 
C=C stretching alkene monosubstituted 
1620-1610 strong 
 
C=C stretching α,β-unsaturated 
 
ketone 
1600-1300 cm
-1
 
1550-1500 
1372-1290 
strong 
 
N-O stretching nitro compound 
 
1465 medium 
 
C-H bending alkane methylene group 
1450 
1375 
medium 
 
C-H bending alkane methyl group 
1390-1380 medium 
 
C-H bending aldehyde 
 
1385-1380 
1370-1365 
medium 
 
C-H bending alkane gem dimethyl 
1400-1000 cm
-1
 
1440-1395 medium 
 
O-H bending carboxylic acid 
 
1420-1330 medium 
 
O-H bending alcohol 
 
1415-1380 
1200-1185 
strong 
 
S=O stretching sulfate 
 
1410-1380 
1204-1177 
strong 
 
S=O stretching sulfonyl chloride 
 
1400-1000 strong 
 
C-F stretching fluoro compound 
 
1390-1310 medium 
 
O-H bending phenol 
 
1372-1335 
1195-1168 
strong 
 
S=O stretching sulfonate 
 
1370-1335 
1170-1155 
strong 
 
S=O stretching sulfonamide 
 
1350-1342 
1165-1150 
strong 
 
S=O stretching sulfonic acid 
anhydrous 
hydrate: 1230-1120 
1350-1300 
1160-1120 
strong 
 
S=O stretching sulfone 
 
1342-1266 strong 
 
C-N stretching aromatic amine 
 
1310-1250 strong 
 
C-O stretching aromatic ester 
 
1275-1200 
1075-1020 
strong 
 
C-O stretching alkyl aryl ether 
 
1250-1020 medium 
 
C-N stretching amine 
 
1225-1200 
1075-1020 
strong 
 
C-O stretching vinyl ether 
 
1210-1163 strong 
 
C-O stretching ester 
 
1205-1124 strong 
 
C-O stretching tertiary alcohol 
 
1150-1085 strong 
 
C-O stretching aliphatic ether 
 
1124-1087 strong 
 
C-O stretching secondary alcohol 
 
1085-1050 strong 
 
C-O stretching primary alcohol 
 
1070-1030 strong 
 
S=O stretching sulfoxide 
 
1050-1040 strong broad 
CO-O-
CO 
stretching anhydride 
 
1000-650 cm
-1
 
995-985 
915-905 
strong 
 
C=C bending alkene monosubstituted 
980-960 strong 
 
C=C bending alkene disubstituted (trans) 
895-885 strong 
 
C=C bending alkene vinylidene 
850-550 strong 
 
C-Cl stretching halo compound 
 
840-790 medium 
 
C=C bending alkene trisubstituted 
730-665 strong 
 
C=C bending alkene disubstituted (cis) 
690-515 strong 
 
C-Br stretching halo compound 
 
600-500 strong 
 
C-I stretching halo compound 
 
900-700 cm
-1
 
880 ± 20 
810± 20 
strong 
 
C-H bending 1,2,4- 
 
880 ± 20 
780 ± 20 
(700 ± 20) 
strong 
 
C-H bending 1,3- 
 
810 ± 20 strong 
 
C-H bending 1,4- and 1,2,3,4- 
 
780 ± 20 
(700 ± 20) 
strong 
 
C-H bending 1,2,3- 
 
755 ± 20 strong 
 
C-H bending 1,2- 
 
750 ± 20 
700 ± 20 
strong 
 
C-H bending 
monosubstituted 
benzene derivative 
 
References 
 
1. Bellamy, L. J., "The Infrared Spectra of Complex Molecules", 2
nd
 edition, John Wiley & Sons, New 
York, 1961. 
2. Nakanishi, K. "Infrared Absorption spectroscopy - Practical", Holden-Day, Inc., San Francisco, 1962.