Characteristic peaks for common functional groups:
| FUNCTIONAL GROUP | BONDS- | BONDS- | |||
| ALKANES | C-H | ||||
| ALKENES | C-H | C=C | C-H bend | ||
| AROMATICS | C-H | C=C | C-H bend | ||
| ALKYNES | terminal | C-H |
|
C-H bend | |
| internal | |
||||
| NITRILES | |
||||
| ALCOHOLS | O-H | C-O stretch | |||
| PHENOLS | O-H | C-O stretch | |||
| ETHERS | C-O stretch | ||||
| AMINES | primary | N-H | N-H bend | C-N stretch | |
| secondary | N-H | N-H bend | C-N stretch | ||
| tertiary | C-N stretch | ||||
| ALDEHYDES | C-H | C=O | |||
| KETONES | C=O | ||||
| ACIDS | O-H | C=O | C-O stretch | ||
| ANHYDRIDES | C=O | ||||
| ACID CHLORIDES | C=O | ||||
| ESTERS | C=O | C-O stretch | |||
| AMIDES | N-H | C=O | N-H bend | C-N stretch | |
| NITRO | N=O | ||||
| HALIDES | C-X | ||||
FUNCTIONAL GROUP REGION (4000 - ~1600
cm-1)
(to the fingerprint region) (to the top)
| BOND | FUNCTIONAL GROUP | FREQUENCY RANGE |
NOTES | ||
| O-H | alcohol | 3600-3200 | |||
| O-H | phenol | 3400-3200 | |||
| O-H | carboxylic acid | 3550-2500 | broad | ||
| N-H | amine | primary | 3500, 3400 | 2 peaks | |
| N-H | secondary | 3450 | 1 peak | ||
| N-H | amide | 3500-3300 | primary: 2 peaks
secondary: 1 peak |
||
| C-H | sp | alkyne(terminal) | 3330-3270 | ||
| C-H | sp2 | alkene | 3100-3010 | ||
| C-H | aromatic | 3100-3010 | |||
| C-H | aldehyde | 2820,2720 | 2 peaks | ||
| C-H | sp3 | alkane | 2950-2850 | ||
 |
nitrile | 2300-2200 | |||
 |
alkyne | 2260-2100 | peak for an internal alkyne may be too weak to be visible | ||
| C=O | anhydride | 1820, 1760 | 2 peaks | ||
| C=O | acid chloride | 1815-1785 | |||
| C=O | ester | 1750-1735 | |||
| C=O | aldehyde | 1740-1720 | |||
| C=O | ketone | ~1715 | |||
| C=O | carboxylic acid | ~1710 | |||
| C=O | amide | 1695-1650 | |||
| conjugated C=O peaks are shifted to lower frequency | |||||
| C=C | alkene | 1670-1640 | |||
| C=C | aromatic | ~1625 | |||
| C=C | conjugated alkene | ~1600 | |||
FINGERPRINT REGION (~1600 - 600 cm-1)
(to the functional group region) (to the top)
The information below for peaks which occur in the fingerprint region
may be useful to confirm the presence of functional groups which also show
peaks in the functional goup region, or to provide structural information
about substitution patterns for alkenes and aromatics.
| GROUP | BOND | FREQUENCY RANGE |
|
| amine | N-H bend | 1630-1560 | |
| amine | C-N stretch | 1360-1020 | |
| amide | N-H bend | 1600-1500 | |
| amide | C-N stretch | ~1400 | |
| nitro | N=O | 1570-1500, 1370-1300 | 2 peaks |
| C-O stretch: | |||
| alcohol | C-O | 1150-1050 | |
| phenol | C-O | 1330-1390, 1260-1180 |
2 peaks |
| ether | C-O | 1150-1070 | symmetrical (R-O-R) |
| C-O | 1275-1200, 1075-1020 |
unsymmetrical (R-O-R'); 2 peaks | |
| acid | C-O | 1320-1210 | |
| ester | C-O | 1275-1020 | |
| alkene | C-H bending: | ||
| R-CH=CH2 | 995-985, 915-905 | 2 peaks | |
| R2C=CH2 | 900-880 | ||
| R-CH=CH-R (Z) | 765-730 | ||
| (E) | 990-960 | ||
| R2C=CH-R | 840-790 | ||
| aromatic | C-H bending: | ||
| monosubstituted | 770-730, 710-690 | 2 peaks | |
| disubstituted:
1,2 (ortho) |
770-735 |
||
| 1,3 (meta) | 810-750, 725-680 | 2 peaks | |
| 1,4 (para) | 840-790 | ||
| alkyne | C-H | 700-610 | |
| halides | C-Cl | 850-550 | |
| C-Br | 690-515 | ||
| C-I | 600-500 |
REFERENCES
Spectrometric Identification of Organic Compounds; R.M.Silverstein, F.X.Webster, 6th edition, John Wiley & Sons, 1998.
Organic Spectroscopy; W.Kemp, 3rd edition, W.H.Freeman and Co., 1991.
Spectroscopic Techniques for Organic Chemists; J.W.Cooper, John Wiley & Sons, 1980.
Spectroscopic methods in organic chemistry; D.H.Williams, I.Fleming, 4th edition, McGraw Hill, 1987.