Infrared spectroscopy correlation table
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- Further information: Infrared spectroscopy
| Bond | Type of bond | Specific type of bond | Absorption range and intensity |
|---|---|---|---|
| C-H | alkyl | methyl | 1380 cm-1 (weak), 1260 cm-1 (strong) and 2870, 2960 cm-1 (both strong to medium) |
| methylene | 1470 cm-1 (strong) and 2850, 2925 cm-1 (both strong to medium) | ||
| methine | 2890 cm-1 (weak) | ||
| vinyl | C=CH2 | 900 cm-1 (strong) and 2975, 3080 cm-1 (medium) | |
| C=CH | 3020 cm-1 (medium) | ||
| monosubstituted alkenes | 900, 990 cm-1 (both strong) | ||
| cis-disubstituted alkenes | 670-700 cm-1 (strong) | ||
| trans-disubstituted alkenes | 965 cm-1 (strong) | ||
| trisubstituted alkenes | 800-840 cm-1 (strong to medium) | ||
| aromatic | benzene/sub. benzene | 3070 cm-1 (weak) | |
| monosubstituted benzene | 700-750 cm-1 (strong) and 700±10 cm-1 (strong) | ||
| ortho-disub. benzene | 750 cm-1 (strong) | ||
| meta-disub. benzene | 750-800 cm-1 (strong) and 860-900 cm-1 (strong) | ||
| para-disub. benzene | 800-860 cm-1 (strong) | ||
| alkynes | 3300 cm-1 (medium) | ||
| aldehydes | 2720, 2820 cm-1 (medium) | ||
| C-C | acyclic C-C | monosub. alkenes | 1645 cm-1 (medium) |
| 1,1-disub. alkenes | 1655 cm-1 (medium) | ||
| cis-1,2-disub. alkenes | 1660 cm-1 (medium) | ||
| trans-1,2-disub. alkenes | 1675 cm-1 (medium) | ||
| trisub., tetrasub. alkenes | 1670 cm-1 (weak) | ||
| conjugated C-C | dienes | 1600, 1650 cm-1 (strong) | |
| with benzene ring | 1625 cm-1 (strong) | ||
| with C=O | 1600 cm-1 (strong) | ||
| aromatic C=C | 1450, 1500, 1580, 1600 cm-1 (strong to weak) — usually 3 or 4 | ||
| C≡C | terminal alkynes | 2100-2140 cm-1 (weak) | |
| disubst. alkynes | 2190-2260 cm-1 (very weak, sometimes not visible) | ||
| C=O | aldehyde/ketone | saturated aliph./cyclic 6-membered | 1720 cm-1 |
| α,β-unsaturated | 1685 cm-1 (goes for aromatic ketones as well) | ||
| cyclic 5-membered | 1750 cm-1 | ||
| cyclic 4-membered | 1775 cm-1 | ||
| aldehydes | 1725 cm-1 (influence of conjugation like with ketones) | ||
| carboxylic acids/derivates | saturated carboxylic acids | 1710 cm-1 | |
| unsat./aromatic carb. acids | 1680-1690 cm-1 | ||
| esters and lactones | 1735 cm-1 (influence of conjugation and ring size like with ketones) | ||
| anhydrides | 1760 and 1820 cm-1 (both!) | ||
| halogenides | 1800 cm-1 | ||
| amides | 1650 cm-1 (associated amides) | ||
| carboxylates (salts) | 1550-1610 cm-1 (goes for aminoacid zwitterions as well) | ||
| O-H | alcohols, phenols | 3610-3670 cm-1 (concentrating samples broadens the band and moves it to 3200-3400 cm-1) | |
| carboxylic acids | 3500-3560 cm-1 (concentrating samples broadens the band and moves it to 3000 cm-1) | ||
| N-H | primary amines | doublet between 3400-3500 cm-1 and 1560-1640 cm-1 (strong) | |
| secondary amines | above 3000 cm-1 (medium to weak) | ||
| ammonium ions | broad bands with multiple peaks between 2400-3200 cm-1 | ||
| C-O | alcohols | primary | 1050±10 cm-1 |
| secondary | around 1100 cm-1 | ||
| tertiary | 1150-1200 cm-1 | ||
| phenols | 1200 cm-1 | ||
| ethers | aliphatic | 1120 cm-1 | |
| aromatic | 1220-1260 cm-1 | ||
| carboxylic acids | 1250-1300 cm-1 | ||
| esters | 1100-1300 cm-1 (two bands - distinction to ketones, which do not possess C-O!) | ||
| C-N | aliphatic amines | 1020-1220 cm-1 (often overlapped) | |
| C=N | 1615-1700 cm-1 (similar conjugation effects to C=O) | ||
| nitriles (triple C-N bond) | 2210-2260 cm-1 (unconjugated 2250, conjugated 2230 cm-1) | ||
| isonitriles (R-N-C bond) | 2165-2110 cm-1 (2140 - 1990 cm-1 for R-N=C=S) | ||
| C-X (X=F, Cl, Br, I) | fluoroalkanes | ordinary | 1000-1100 cm-1 |
| trifluromethyl | two strong, broad bands between 1100-1200 cm-1 | ||
| chloroalkanes | 540-760 cm-1 (medium to weak) | ||
| bromoalkanes | below 600 cm-1 | ||
| iodoalkanes | below 600 cm-1 | ||
| N-O | nitro compounds | aliphatic | 1540 cm-1 (stronger band) and 1380 cm-1 (weaker band) - ALWAYS BOTH! |
| aromatic | 1520, 1350 cm-1 (conjugation usually lowers the wave number) |
The absorptions in this range do not apply only to bonds in organic molecules. IR spectroscopy is useful when it comes to analysis of inorganic compounds (such as metal complexes or fluoromanganates) as well.
