An infrared spectroscopy correlation table (or table of infrared absorption frequencies) is a list of absorption peaks and frequencies, typically reported in wavenumber, for common types of molecular bonds and functional groups.[1] [2] In physical and analytical chemistry, infrared spectroscopy (IR spectroscopy) is a technique used to identify chemical compounds based on the way infrared radiation is absorbed by the compound.
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.[3]
Tables of vibrational transitions of stable[4] and transient molecules[5] are also available.
| Bond | Type of bond | Specific type of bond | Absorption peak (cm−1) | Appearance |
|---|---|---|---|---|
| C─H | alkyl | methyl | 1260 | strong |
| 1380 | weak | |||
| 2870 | medium to strong | |||
| 2960 | medium to strong | |||
| methylene | 1470 | strong | ||
| 2850 | medium to strong | |||
| 2925 | medium to strong | |||
| methine | 2890 | weak | ||
| vinyl | C═CH2 | 900 | strong | |
| 2975 | medium | |||
| 3080 | medium | |||
| C═CH | 3020 | medium | ||
| monosubstituted alkenes | 900 | strong | ||
| 990 | strong | |||
| cis-disubstituted alkenes | 670–700 | strong | ||
| trans-disubstituted alkenes | 965 | strong | ||
| trisubstituted alkenes | 800–840 | strong to medium | ||
| aromatic | benzene/sub. benzene | 3070 | weak | |
| monosubstituted benzene | 700–750 | strong | ||
| 690–710 | strong | |||
| ortho-disub. benzene | 750 | strong | ||
| meta-disub. benzene | 750–800 | strong | ||
| 860–900 | strong | |||
| para-disub. benzene | 800–860 | strong | ||
| alkynes | any | 3300 | medium | |
| aldehydes | any | 2720 | medium | |
| 2820 | ||||
| C═C | acyclic C═C | monosub. alkenes | 1645 | medium |
| 1,1-disub. alkenes | 1655 | medium | ||
| cis-1,2-disub. alkenes | 1660 | medium | ||
| trans-1,2-disub. alkenes | 1675 | medium | ||
| trisub., tetrasub. alkenes | 1670 | weak | ||
| conjugated C═C | dienes | 1600 | strong | |
| 1650 | strong | |||
| with benzene ring | 1625 | strong | ||
| with C═O | 1600 | strong | ||
| C═C (both sp2) | any | 1640–1680 | medium | |
| aromatic C═C | any | 1450 | weak to strong (usually 3 or 4) | |
| 1500 | ||||
| 1580 | ||||
| 1600 | ||||
| C≡C | terminal alkynes | 2100–2140 | weak | |
| disubst. alkynes | 2190–2260 | very weak (often indistinguishable) | ||
| C=O | aldehyde/ketone | saturated aliph./cyclic 6-membered | 1720 | |
| α,β-unsaturated | 1685 | |||
| aromatic ketones | 1685 | |||
| cyclic 5-membered | 1750 | |||
| cyclic 4-membered | 1775 | |||
| aldehydes | 1725 | influenced by conjugation (as with ketones) | ||
| carboxylic acids/derivates | saturated carboxylic acids | 1710 | ||
| unsat./aromatic carb. acids | 1680–1690 | |||
| esters and lactones | 1735 | influenced by conjugation and ring size (as with ketones) | ||
| anhydrides | 1760 | |||
| 1820 | ||||
| acyl halides | 1800 | |||
| amides | 1650 | associated amides | ||
| carboxylates (salts) | 1550–1610 | |||
| amino acid zwitterions | 1550–1610 | |||
| O─H | alcohols, phenols | low concentration | 3610–3670 | |
| high concentration | 3200–3400 | broad | ||
| carboxylic acids | low concentration | 3500–3560 | ||
| high concentration | 3000 | broad | ||
| N─H | primary amines | any | 3400–3500 | strong |
| 1560–1640 | strong | |||
| secondary amines | any | >3000 | weak to medium | |
| ammonium ions | any | 2400–3200 | multiple broad peaks | |
| C─O | alcohols | primary | 1040–1060 | strong, broad |
| secondary | ~1100 | strong | ||
| tertiary | 1150–1200 | medium | ||
| phenols | any | 1200 | ||
| ethers | aliphatic | 1120 | ||
| aromatic | 1220–1260 | |||
| carboxylic acids | any | 1250–1300 | ||
| esters | any | 1100–1300 | two bands (distinct from ketones, which do not possess a C─O bond) | |
| C─N | aliphatic amines | any | 1020–1220 | often overlapped |
| C═N | any | 1615–1700 | similar conjugation effects to C═O | |
| C≡N (nitriles) | unconjugated | 2250 | medium | |
| conjugated | 2230 | medium | ||
| R─N─C (isocyanides) | any | 2165–2110 | ||
| R─N═C═S (isothiocyanates) | any | 2140–1990 | ||
| C─X | fluoroalkanes | ordinary | 1000–1100 | |
| trifluoromethyl | 1100–1200 | two strong, broad bands | ||
| chloroalkanes | any | 540–760 | weak to medium | |
| bromoalkanes | any | 500–600 | medium to strong | |
| iodoalkanes | any | 500 | medium to strong | |
| N─O | nitro compounds | aliphatic | 1540 | stronger |
| 1380 | weaker | |||
| aromatic | 1520 | lower if conjugated | ||
| 1350 | ||||
| P─C | Organophosphorus compound | aromatic | 1440-1460 | medium |
| P─O | phosphorus oxide | bonded | 1195-1250 | strong |
| free | 1250-1300 | strong |