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Table of IR Spectroscopy Values

Core Concepts

This article will provide a table containing the IR spectrum frequency values and the molecules they represent.

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Table of IR Spectrum Frequency Values

IR Spectrum Stretching Vibrations

Bond OrderFrequencyStructural UnitAppearance of the Peak
Single Bonds3200–3600O-H (Alcohol)Broad
2500–3350O-H (Carboxylic acids)Broad and zig-zagged
3300–3500N-H (Primary or secondary Amine)Broad
Primary amines display 2 peaks,
because they have 2 N-H bonds
Secondary amines display only
1 peak (1 N-H bond)
3310–3320C-H (Alkane)
3000–3100C-H (Alkene)
2850–2950C-H (Alkyne)Sharp
2695-2830C-H (Aldehyde)Doublet
2800-3000N-H (Amine Salt)
2550-2600S-H (Thiol)Weak
1500-1550N-O (nitro compound)Strong
1200C-O (sp2 carbon)
1025–1200C-O (sp3 carbon)
1000-1400C-F (fluoro compound)Strong
550-850C-Cl stretchingStrong
515-690C-Br stretchingStrong
600500-C-I stretchingStrong
Double Bonds1740–1790 and 1800–1850C=O (Acid anhydrides)Strong and very sharp
1770–1815C=O (Acyl halides)Strong and very sharp
1760C=O (Carboxylic acid monomer)Strong
1730–1750C=O (Esters)Strong and very sharp
1720-1740C=O (Aldehyde)Strong
1715-1730C=O (α,β-unsaturated ester)Strong
1710–1750C=O (Carbonyl carbon in aldehydes and ketones)Strong and very sharp
1705-1725C=O (Aliphatic ketone)Strong
1700–1720C=O (Carboxylic acid dimer)Strong and very sharp
1690C=O (Primary Amides)Strong
1685-1710C=O (Conjugated Aldehyde)Strong
1680C=O (Secondary or Tertiary Amides)Strong and very sharp
1666-1685C=O (Conjugated ketone)Strong
1640-1690C=N ( imine / oxime )Medium
1380-1415S=O (sulfate)Strong
1380-1410S=O (sulfonyl chloride)Strong
1342-1350S=O (sulfonic acid)Strong
1335-1372S=O (sulfonate)Strong
1335-1370S=O (sulfonamide)Strong
1300-1350S=O (sulfone)Strong
1030-1070S=O (sulfoxide)Strong
Triple Bonds2240–2280C≡N (Nitrile)Weak
2175-2140S-C≡N (thiocyanate)Strong
2190–2260C≡C (Disubstituted Alkyne)Weak
2100-2140C≡C (Monosubstituted Alkyne)Weak
List of stretching vibrations in descending order of frequency

IR Spectrum Bending Vibrations

Classification FrequencyStructural UnitAppearance of the Peak
Alkenes910, 990C=C bending
Monosubstituted terminal alkene
RCH=CH2
890C=C bending
Disubstituted terminal alkene
R2C=CH2
960–980C=C bending
Disubstituted trans alkene
trans RCH=CHR’
Strong
790–840C=C bending
Trisubstituted alkene
R2C=CHR’
Medium
665–730C=C bending
Disubstituted cis alkene
cis RCH=CHR’
Strong
Substituted
Derivates
of Benzene
730–770 and 690–710C-H bending
Monosubstituted benzene ring
Strong
735–770C-H bending
Ortho-disubstituted
Strong
750–810 and 680–730C-H bending
Meta-disubstituted
Strong
790–840C-H bending
Para-disubstituted
Strong
Bending vibrations in descending order of frequency

IR Spectrum Exercises

After taking note of these values, put your knowledge to the test using Cheminfo’s interactive IR exercises
IR spectrum analysis can be a little intimidating at the beginning, but remember, the more you practice, the easier it becomes

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