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Infrared Tables (short summary of common absorption frequencies)
The values given in the tables that follow are typical values. Specific bands may fall over a range of
wavenumbers, cm
. Specific substituents may cause variations in absorption frequencies. Absorption
intensities may be stronger or weaker than expected, often depending on dipole moments. Additional
bands may confuse the interpretation. In very symmetrical compounds there may be fewer than the
expected number of absorption bands (it is even possible that all bands of a functional group may
disappear, i.e. a symmetrically substituted alkyne!). Infrared spectra are generally informative about
what functional groups are present, but not always. The 1 H and 13 C NMR’s are often just as
informative about functional groups, and sometimes even more so in this regard. Information obtained
from one spectroscopic technique should be verified or expanded by consulting the other spectroscopic
techniques.
IR Summary - All numerical values in the tables below are given in wavenumbers, cm
-
Bonds to Carbon (stretching wave numbers)
C C
not used
C N
1000-
C C C^ C
C O
1050-
C C (^) C N
C O
1250
1100-
1600-
sp^3 C-X single bonds (^) sp 2 C-X single bonds
sp^2 C-X double bonds sp C-X triple bonds
C N
1640-
C O
1640-
C N
2100-2250 2240-
Stronger dipoles produce more intense IR bands and weaker dipoles produce less intense IR bands (sometimes none).
expanded table on next page
not very useful alkoxy C-O not very useful acyl and phenyl C-O
Bonds to Hydrogen (stretching wave numbers)
C H
C C H C H
O
C N
H
H
sp^3 C-H
sp^3 C-H sp^3 C-H aldehyde C-H (two bands)
primary NH 2 (two bands) (^) alcohol O-H
secondary N-H (one band) acid O-H (^) thiol S-H
C H
C N
H 3100- 3200-
R O H
C O H
O
(very weak)
R S H
amides = strong, amines = weak
(see sp^2 C-H bend patterns below) (sp C-H bend^ ≈^ 620)
Carbonyl Highlights (stretching wave numbers)
C
O
R H
Aldehydes (^) Ketones Acids
Amides Anhydrides^ Acid Chlorides
saturated = 1725 conjugated = 1690 aromatic = 1700
C
O
R R saturated = 1715 conjugated = 1680 aromatic = 1690 6 atom ring = 1715 5 atom ring = 1745 4 atom ring = 1780 3 atom ring = 1850
C
O
R O saturated = 1735 conjugated = 1720 aromatic = 1720 6 atom ring = 1735 5 atom ring = 1775 4 atom ring = 1840
Esters
C
O
R O saturated = 1715 conjugated = 1690 aromatic = 1690
C
O
R NR (^2) saturated = 1650 conjugated = 1660 aromatic = 1660 6 atom ring = 1670 5 atom ring = 1700 4 atom ring = 1745 3 atom ring = 1850
saturated = 1760, 1820 conjugated = 1725, 1785 aromatic = 1725, 1785 6 atom ring = 1750, 1800 5 atom ring = 1785, 1865
C
O
R Cl saturated = 1800 conjugated = 1770 aromatic = 1770
C
O
R O
O
R
R' H
R N
O
O
nitro
asymmetric = 1500- symmetric = 1300-
Very often there is a very weak C=O overtone at approximately 2 x ν (≈3400 cm-1^ ). Sometimes this is mistaken for an OH or NH peak.,
sp^2 C-H bend patterns for alkenes sp^2 C-H bend patterns for aromatics
alkene substitution pattern
aromatic substitution pattern
descriptive alkene term
descriptive aromatic term
absorption frequencies (cm-1^ ) due to sp 2 CH bend
absorption frequencies (cm-1^ ) due to sp^2 CH bend
C C
R
H
H
H
C C
R
H
R
H
monosubstituted alkene
cis disubstituted alkene
trans disubstituted alkene
geminal disubstituted alkene
trisubstituted alkene
tetrasubstituted alkene
985- 900-
675- (broad)
880-
960-
790-
none
X
X
X
X
X
X
X
monosubstituted aromatic
ortho disubstituted aromatic
meta disubstituted aromatic
para disubstituted aromatic
Aromatic compounds have characteristic weak overtone bands that show up between 1650-2000 cm-1^ ). Some books provide pictures for comparison (not here). A strong C=O peak will cover up most of this region.
C C
R
H
H
R
C C
R
R
H
H
C C
R
R
R
H
C C
R
R
R
R
690- 730-
735-
680- 750- 880-900 (sometimes)
790-
IR Flowchart to determine functional groups in a compound (all values in cm-1^ ).
has C=O band (1650-1800 cm-1^ ) very strong
does not have C=O band
IR Spectrum
aldehydes
C
O
aldehyde C-H
1725-1740 (saturated) 1660-1700 (unsaturated) 2860- 2760- (both weak)
ketones
C
O (^) 1710-1720 (saturated) 1680-1700 (unsaturated) 1715-1810 (rings: higher in small rings) esters - rule of 3
C
O
(1000-1150, alkoxy, medium)
1735-1750 (saturated) 1715-1740 (unsaturated) 1735-1820 (higher in small rings)
C O acids
C
O
1210-1320 (acyl, strong)
1700-1730 (saturated) 1715-1740 (unsaturated) 1680-1700 (higher in small rings)
C O
O H
acid (^) 2400-3400, very broad (overlaps C-H stretch) amides
C
O 1630-1680 (saturated) 1745 (in 4 atom ring)
N
H
H
N H
3350 & 3180, two bands for 1o^ amides, one band for 2 o^ amides, stronger than in amines, extra overtone sometimes at 3100
N-H bend, 1550-1640, stronger in amides than amines N H
acid chlorides
C
O 1800 (saturated) 1770 (unsaturated)
anhydrides
C
O
1150-1350 (acyl, strong)
1760 & 1820 (saturated) 1725-1785 (unsaturated) two strong bands
C O
nitriles ≈^2250 sharp, stronger than alkynes, a little lower when conjugated
alkanes
C C C N
alkynes
alkenes
aromatics
alcohols
thiols
amines
ethers
nitro compounds
N O
O
carbon-halogen bonds
sp^3 C-H stretch sp 3 C-H bend C C not useful
1460 & 1380
2850-
C X (^) usually not very useful
sp^2 C-H stretch
sp^2 C-H bend
C C (^) weak or not present1600-
650- (see table for spectral patterns)
3000-
sp^2 C-H stretch 3050-
sp^2 C-H bend
690-900 (see table), overtone patterns between 1660-
C C 1600 & 1480 can be weak
O H
alcohol
C O
3600- 1000- (3o^ > 2o^ > 1 o^ )
S H
thiol ≈^ 2550 (weak)
N
H
H
N H
3300 - 3500, two bands for 1o^ amines, one band for 2o^ amines, weaker than in amides, N-H bend, 1550-1640, stronger in amides than amines N H
N C 1000- (uncertain)
1120 (alphatic) C O 1040 & 1250 (aromatic)
1500-1600, asymmetric (strong) 1300-1390, symmetric (medium)
C N
C C
sp C-H stretch
sp C-H bend
2150 (variable intensity)
3300 sharp, strong 620
not present or weak when symmetrically substituted, a little lower when conjugated
sometimes lost in sp^3 CH peaks
C O
acyl alkoxy
1150-1350 (acyl, strong)
acyl
1 o 2 o
Inductive pull of Cl increases the electron density between C and O.
acyl
All IR values are approximate and have a range of possibilities depending on the molecular environment in which the functional group resides. Resonance often modifies a peak's position because of electron delocalization (C=O lower, acyl C-O higher, etc.). IR peaks are not 100% reliable. Peaks tend to be stronger (more intense) when there is a large dipole associated with a vibration in the functional group and weaker in less polar bonds (to the point of disappearing in some completely symmetrical bonds).
1 o 2 o
alkoxy
(easy to overlook)
alkoxy
X = F, Cl, Br, I
Alkene sp 2 C-H bending patterns
monosubstituted alkene (985-1000, 900-920) geminal disubstituted (960-990) cis disubstituted (675-730) trans disubstituted (880-900) trisubstituted (790-840) tetrasubstituted (none, no sp^2 C-H)
Aromatic sp^2 C-H bending patterns
monosubstituted (730-770, 690-710) ortho disubstituted (735-770) meta disubstituted (880-900,sometimes, 750-810, 680-725) para disubstituted (790-840)
There are also weak overtone bands between 1660 and 2000, but are not shown here. You can consult pictures of typical patterns in other reference books. If there is a strong C=O band, they may be partially covered up.
(^1211109876543210)
(^240220200180160140120100806040200)
typical proton chemical shifts
typical carbon-13 chemical shifts
simple sp 3 C-H CH > CH 2 > CH 3
C C C
O C
OC
H
X C X = F,Cl,Br,I
C H
alcohol O H
allylic C-H
benzylic C-H carbonyl alpha C-H
amine N-H
epoxide C-H
alkene C-H
aldehyde C-H aromatic C-H
carboxylic acid O-H
amide N-H
alcohols ethers esters
shielding side = more electron rich (inductive & resonance)
deshielding side = less electron rich (inductive & resonance)
alcohols, ethers, esters
C C N C
carboxylic acids anhydrides esters amides acid chlorides
R
C
O
X
R
C
O
R ketones
R
C
O
H aldehydes
halogen C
PPM
PPM
F ≈ 80- Cl ≈ 45- Br ≈ 35- I ≈ 15-
210 180
180 160
220 +^180
125 110
90 + 70 -
160 +^100 - 60 +^0
80 + 50
95 15
10 9 8 + 6 5 + 3.3 3 2 2 0.
12 10
7 +^4
3.5 2.
3 + 2
5 3 2.5 1.
(^6 )
1
2 1
5
simple sp^3 carbon C > CH > CH 2 > CH 3
no H
with H
no H
with & without H
no H
with & without H
with & without H
with & without H
with & without H
Carbon and/or heteroatoms without hydrogen do not appear here, but influence on any nearby protons may be seen in the chemical shifts of the protons.
O
epoxides with & without H 60 40 S C
with & without H
thiols, sulfides
40 20
thiol SH 1.5 1.
thiols, sulfides 2.5 2.
50 30
N C
with & without H
amines, amides
amines
H 3.0 2.
S C H
N C H
Typical 1 H and 13 C NMR chemical shift values.
CH 3 O
C
C
H
H
H
Example Calculation
δb = 5.2 + (-0.6) = 4. actual = 4.6 (J = 6, 1.6 Hz)
C C
H
gem
cis
trans δ(ppm) = 5.2 + α (^) gem + α (^) cis + α (^) trans
Substitution relative to calculated "H"
gem
trans
cis
δ gem = 5.2 + 1.4 = 6. actual = 6.
δ trans = 5.2 - 0.1 = 5. actual = 5.
δ cis = 5.2 + 0.4 = 5. actual = 5.
Estimated chemical shifts for protons at alkene sp 2 carbons
Substituent α (^) geminal α (^) cis α (^) trans
H- 0.0 0.0 0. Hydrogen R- 0.5 -0.2 -0. Alkyl C 6 H 5 CH 2 - 0.7 -0.2 -0. Benzyl X-CH 2 - 0.7 0.1 0. Halomethyl (H)/ROCH 2 - 0.6 0.0 0. alkoxymethyl (H) 2 /R 2 NCH 2 - 0.6 -0.1 -0. aminomethyl RCOCH 2 - 0.7 -0.1 -0.
α-keto NCCH 2 - 0.7 -0.1 -0.
α-cyano R 2 C=CR- 1.2 0.0 0. Alkenyl C 6 H 5 - 1.4 0.4 -0. Phenyl F- 1.5 -0.4 -1. Fluoro Cl- 1.1 0.2 0. Chloro Br- 1.1 0.4 0. Bromo I- 1.1 0.8 0. Iodo RO- 1.2 -1.1 -1. akoxy (ether) RCO 2 - 2.1 -0.4 -0. O-ester (H) 2 /R 2 N- 0.8 -1.3 -1. N-amino RCONH- 2.1 -0.6 -0. N-amide O 2 N- 1.9 1.3 0. Nitro RS- 1.1 -0.3 -0. Thiol OHC- 1.0 1.0 1. Aldehyde ROC- 1.1 0.9 0. Ketone HO 2 C- 0.8 1.0. 03 C-acid RO 2 C- 0.8 1.0 0. C-ester H 2 NOC- 0.4 1.0 0. C-amide NC- 0.3 0.8 0. Nitrile
C C
H
H
H
O C
O
C C
H H
a H
b
c (^) d e
f
δa = 5.2 + (-0.4) = 4. actual = 4.9 (J = 14, 1.6 Hz)
δc = 5.2 + 2.1 = 7. actual = 7.4 (J = 14, 6 Hz) δd = 5.2 + 0.8 = 6. actual = 6.2 (J = 18, 11 Hz) δe = 5.2 + 0.5 = 5. actual = 5.8 (J = 11, 1.4 Hz) δf = 5.2 + 1.0 = 6. actual = 6.4 (J = 18, 1.4 Hz)
Estimated chemical shifts for protons at aromatic sp 2 carbons
Substituent α ortho α meta α para
H- 0.0 0.0 0. Hydrogen CH 3 -^ -0.2^ -0.1^ -0. Methyl ClCH 2 - 0.0 0.0 0. Cholromethyl Cl 3 C- 0.6 0.1 0. Halomethyl HOCH 2 - -0.1 -0.1 -0. Hydroxymethyl R 2 C=CR- 0.1 0.0 -0. Alkenyl C 6 H 5 - 1.4 0.4 -0. Phenyl F- -0.3 0.0 -0. Fluoro Cl- 0.0 0.0 -0. Chloro Br- 0.2 -0.1 0. Bromo I- 0.4 -0.2 0. Iodo HO- -0.6 -0.1 -0. Hydroxy RO- -0.5 -0.1 -0. Alkoxy RCO 2 - -0.3 0.0 -0. O-ester (H) 2 /R 2 N- -0.8 -0.2 -0. N-amino RCONH- 0.1 -0.1 -0. N-amide O 2 N- 1.0 0.3 0. Nitro RS- -0.1 -0.1 -0. thiol/sulfide OHC- 0.6 0.2 0. Aldehyde ROC- 0.6 0.1 0. Ketone HO 2 C- 0.9 0.2 0. C-acid RO 2 C- 0.7 0.1 0. C-ester H 2 NOC- 0.6 0.1 0. C-amide NC- 0.4 0.2 0. Nitrile
δ(ppm) = 7.3 + α (^) ortho + α (^) meta + α (^) para
Substitution relative to calculated "H"
H
meta ortho
para
meta (^) ortho
Example Calculation
CH 3 O
H
H
H
H CH 2
H
H
H
- δ (CH 3 ) = 0.9 + 2.8 = 3. actual = 3.
- δ (2) = 7.3 + (-0.5) (^) ortho + (-0.1) (^) para = 6. actual = 6.
- δ (3) = 7.3 + (-0.2) (^) ortho + (-0.4) (^) para = 6. actual = 7.
- δ (CH 2 ) = 1.2 + (0.8)α + (1.4)α = 3. actual = 3.
- δ (5) = 5.2 + (0.7) (^) gem = 5. actual = 5.
- δ (6) = 5.2 + (-0.2) (^) trans = 5. actual = 5.
- δ (7) = 5.2 + (-0.2) (^) cis = 5. actual = 5.
Proton chemical shifts of hydrogen on sp^3 carbons depend on two main factors (electronegativity and pi
bond anisotropy). All values listed below are only approximate and have a small plus or minus range
about the listed value.
All things being equal, methine protons (CH) have greater chemical shifts than methylene protons (CH 2 ) which have greater chemical shifts than methyl protons (CH 3 ).
C H (^) C H
H C H
H
H
Chemical shifts in an only "alkane" environment.
δ 1.5 ppm δ 1.2 ppm^ δ 0.9 ppm methine protons methylene protons^ methyl protons
1. sp
3
C-H Electronegative atoms in the vicinity of hydrogen deshield protons and produce a larger
chemical shift. If the electronegative atom is in resonance with an adjacent pi system that further
withdraws electron density, the chemical shift is increased.
(r esonance withdrawal)
C F
H C Cl
H C Br
H C I
H
C N
H
δ 2.3 - 3.1 ppm
δ 4.1 - 4.7 ppm
C OH
H C OR
H C O
H (^) C
O R C O
H C O
H (^) C
O
δ 3.1 - 3.7 ppm (^) δ 3.0 - 3.6 ppm δ 2.9 - 3.5 ppm
amines amides
fluoro alkanes (^) chloro alkanes (^) bromo alkanes iodo alkanes
δ 3.1 - 3.7 ppm alcohol alkyl ether (^) aromatic ether alkyl ester (oxygen side)
aromatic ester (oxygen side)
δ 3.0 - 3.6 ppm^ δ 3.7 - 4.3 ppm^ δ^ 3.7 - 4.3 ppm^ δ^ 4.0 - 4.6 ppm
C SH
H C SR
H
δ 2.2 - 2.8 ppm thiol alkyl ether
δ 2.2 - 2.8 ppm
(resonance withdrawal) (resonance withdrawal) (resonance withdrawal)
C
O
H δ 2.5 - 3.2 ppm epoxide ether
a. next to a halogen
b. next to a oxygen
c. next to a sulfur or nitrogen
δ 3.0 - 3.6 ppm
C N
H (^) C
O
2. sp
3
C-H Pi bonds in the vicinity of hydrogen also deshield protons via pi bond anisotropy and
produce a larger chemical shift. The closer the sp
3
C-H is to the pi bond the greater chemical shift
observed. When an electronegative atom is part of the pi bond, the chemical shift also increases.
C C
H (^) O
aldehydes, ketones, carboxylic acids, amides, alkyl ester (oxygen side)
aromatic ketones
δ 1.9 - 2.7 ppm δ 2.6 - 3.3 ppm
C C
H (^) O
(resonance withdrawal)
acid chlorides
δ 2.7 - 3.4 ppm (resonance withdrawal)
C C
H (^) O
Cl
nitro compounds
δ 2.7 - 3.4 ppm (resonance withdrawal)
C N
H (^) O
O
C C
H (^) C
allylic protons
δ 1.7 - 2.3 ppm
C
H
benzylic protons
δ 2.3 - 2.9 ppm propargylic protons
δ 1.8 - 2.4 ppm
C
H C C
3. sp^2 C-H Hydrogens at the side of a pi bond are deshielded even more than above via pi bond
anisotropy. An aldehyde produces the largest effect due to the electronegative oxygen, followed by an
aromatic ring, followed by alkenes and finally terminal alkynes. (One sp C-H)
vinylic protons (resonance and inductive withdrawal)
R C
C
H
H H
simple vinylic protons
δ 5.7 ppm
δ 5.0 ppm
C C
C
H
H O H
δ 6.0 - 6.3 ppm
δ 5.5 - 6.5 ppm
RO C
C
H
H H
δ 6.4 - 7.4 ppm
δ 4.0 - 4.6 ppm
vinylic protons (resonance donation and inductive withdrawal)
aromatic protons (resonance and inductive withdrawal)
simple aromatic protons
δ 7.1 - 7.3 ppm
aromatic protons (resonance donation and inductive withdrawal)
H
R
H
C
O
δ 7.9 - 8.3 ppm
H
O
δ 6.7 - 7.0 ppm H
N
δ 6.5 - 7.0 ppm
aldehydes
δ 9 - 10 ppm
C
O
H
alkene C-H
aromatic C-H
aldehyde C-H (^) alkyne C-H
C C H
terminal alkyne protons
δ 1.9 - 3.2 ppm
C C
C
H
H O H RO C
C
H
H H
4. There are several kinds of hydrogen attached to heteroatoms. Some of these are listed below. Often
these hydrogens do not follow the N+1 rule because they exchange via acid/base proton exchanges and
are not next to neighbor protons long enough to allow coupling to be observed. They are often
observed as broad singlets (sometimes so broad they are not easily seen in the spectra). If the
exchange rate is very fast among the exchangeable protons on the NMR time scale, all of the
exchangeable protons may appear together at a single, averaged chemical shift.
alcohols
δ 1 - 5 ppm
O
H
phenol and enol protons
δ 7 - 15 ppm
O
H
O
H
amines
δ 1 - 2 ppm
N
H
carboxylic acids
δ 10 - 12 ppm
C
O
O H
C
O
N H
amides
δ 1 - 6 ppm
- One nearest neighbor proton
∆E (^) to flip proton
increasing δ increasing ∆E (ν, B (^) o )
the ratio of these two populations is about 50/50 (or 1:1)
∆E 1 (observed)
∆E 2 (observed)
observed proton
one neighbor proton = Ha
B (^) o
Protons in this environment have a small additional increment added to the external magnetic field, Bo , and produce a higher energy transition by that tiny amount.
Protons in this environment have a small cancellation of the external magnetic field, B (^) o , and produce a smaller energy transition by that tiny amount.
small difference in energy due to differing neighbor's spin (in Hz)
J = coupling constant
C C
H (^1) H (^) a
H (^1)
C C C C
H (^1)
H (^1)
(^1 )
- Two nearest neighbor protons (both on same carbon or one each on separate carbons)
∆E (^) to flip proton
the ratio of these four populations is about 1:2:
∆E (^1)
observed proton
two neighbor protons
B (^) o
J (Hz)
C C
H (^) a H (^) b
H (^1)
H (^1)
C C
H (^1)
1 2
∆E (^2) ∆E 3 J1a
1
J1b J1b two equal energy two neighbor protons are liketwo small magnets that can be populations here
arranged four possible ways (similar to flipping a coin twice) J (Hz)
- Three nearest neighbor protons (on same carbon, or two on one and one on another, or one each on separate carbons)
∆E (^) to flip proton
the ratio of these eight populations is about 1:3:3: observed proton
three neighbor protons
B (^) o
C C
H (^) a H (^) b H (^) c
H (^1)
H (^1)
C C
H (^1)
3
∆E (^2) ∆E 3 J1a
1
J1b J1b
three equal energy populations at each of middle transitions
three neighbor protons are like three small magnets that can be arranged eight possible ways (similar to flipping a coin thrice)
∆E (^1)
∆E (^4)
3 1
J1c J1c J1c
δ (ppm)
δ (ppm)
δ (ppm)
N + 1 rule (N = # neighbors)
peaks = N + 1 = 1 + 1 = 2 peaks
N + 1 rule (N = # neighbors)
peaks = N + 1 = 2 + 1 = 3 peaks
N + 1 rule (N = # neighbors)
peaks = N + 1 = 3 + 1 = 4 peaks
perturbation(s) by neighbor proton(s)
J (Hz)
J (Hz) J (Hz) J (Hz)
J1a
s = singlet
d = doublet
t = triplet
q = quartet
qnt = quintet
sex = sextet
sep = septet
o = octet
1 peak = 100%
1 peak = 50%
1 peak = 25%
1 peak = 12%
1 peak = 6%
1 peak = 3%
1 peak = 1.5%
1 peak = 0.8%
Multiplets when the N + 1 rule works (all J values are equal).
Combinations or these are possible.
dd = doublet of doublets
ddd = doublet of doublet of doublets
dddd = doublet of doublet of doublet of doublets
dt = doublet of triplets
td = triplet of doublets
etc.
relative sizes of
peaks in multiplets
