IR Absorption Bands of Functional Groups in Organic Compounds
Functional
Group
Alkane
Alkene
Terminal alkyne
(internal alkynes
lack unique
bands)
Alcohol
Wavenumber
(cm-1)
2850-3000
1450-1470
1370-1380
800-1200
720-725
3060-3140
1620-1680
900-1000
3300-3320
2100-2140
600-700
C–H stretch for sp3 carbon (Strong)
C–H bend (Strong)
C–H methyl umbrella bend (Medium)
C–C stretch (many medium bands)
C–H bend (Medium)
C–H stretch for sp2 carbon (Medium)
C=C stretch (Medium)
C–H bend (Strong)
C–H stretch for sp carbon (Medium)
C≡C stretch (medium)
C–H bend (Strong)
3200-3600
H–bonded O–H stretch (Broad strong
band)
Free O–H stretch (sharp medium band,
present only in dilute samples)
C–O stretch (strong, higher ν for more
substituents on carbon)
C–O stretch
N–H stretch (two medium bands)
N–H stretch (single medium band)
3600-3700
1000-1200
Ether
Primary amine
Secondary amine
Nitrile
Aldehyde
Ketone
Carboxylic acid
Ester
Amide
Aromatic
Comments
1050-1150
3200-3400
3200-3400
2220-2280
1700-1720
2700-2850
1680-1720
1700-1720
3000
1730-1750
1000-1300
1650-1690
3200-3400
3000-3150
1750-1950
Nitro
600-900
1550 and 1400
Carbon dioxide
2350
N≡C stretch (medium)
C=O stretch (Strong)
Aldehyde C–H stretch, two medium bands
C=O stretch (Strong)
C=O stretch (Strong)
O–H stretch (very broad band, usually with
a spike of sp3 C–H stretch in the middle)
C=O stretch (Strong)
C–O stretch
C=O stretch (Strong)
N–H stretch (two bands for primary, one for
secondary, none for tertiary amide)
C–H stretch (variable)
C–H bending overtone region (usually
several weak bands of similar strength)
C–H bend (strong)
“Walrus teeth” N–O stretch bands
Doublet (positive or negative, depending on
variation in local concentration between
baseline and sample measurement)
Predicting Chemical Shifts for 1H-NMR Spectra
(adapted from Table 12.4, J.M. Hornback Organic Chemistry, 1998)
Type of
Hydrogen
Chemical Shift
(δ)
Type of
Hydrogen
Chemical Shift
(δ)
C CH3
0.9
Br
CH3
2.7
C C CH3
1.6
Cl
CH3
3.0
C CH
N H
O H
O
C O C CH3
O
C CH3
N CH3
I
CH3
N C CH3
CH3
O CH3
1.8
Variable (1-4)
Variable (2-5)
2.0
2.2
O
C O CH3
O2N CH3
F
CH3
2.2
2.2
2.3
3.7
4.1
4.2
C C H
2.2
3.3
H
O
C N H
O
C H
O
C O H
5.5-6.5
7-8
Variable (6-8)
10
12
Procedure: Find the functional group near the proton of interest. Take the
chemical shift listed and:
Add 0.3 if CH2 instead of CH3, or add 0.7 if CH instead of CH3.
Add 0.3 for electronegative group or atom attached to the adjacent carbon.
When two electronegative groups are attached to the same carbon, both groups
affect the hydrogens: add the indicated values from the table together, add the
correction for the methylenyl or methinyl hydrogen, and subtract 0.9 from the total.
The value obtained by these calculations is a prediction, and may deviate from
observed values by 1 ppm or more.
13C
NMR Chemical Shifts
Chemical Shift
Group
5-40
Ether
15-55
Alkyne
25-60
Alkene
40-50
Aromatic
30-40
Alcohol
5-15
Amine
150-185
Carbonyl
(aldehyde,
ketone)
Group
Methyl
Methylene
Methine
Alkyl chloride
Alkyl bromide
Alkyl iodide
Carbonyl (amide,
carboxylic acid,
ester)
Chemical Shift
55-90
60-90
100-170
90-160
45-90
10-70
175-220
Substituent Effects on Electrophilic Aromatic Substitution
Group
Effect
Regiochemistry
R
NH2
N
OH
O
R
O R
S R
O
O
H
N C R
Ortho/para
Moderately
activating
Ortho/para
Weakly
activating
Ortho/para
Weakly
deactivating
Ortho/para
Moderately
deactivating
Meta
Strongly
deactivating
Meta
O C R
R
Ar
X
O
O
O
C H
C R
C OH
O
O
C NH2
C O R
C N
SO3H
CX3
R
NH3
Strongly
activating
N R
R
NO2