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Infrared Tables (short summary of common absorption frequencies). The values given in the tables that follow are ... carboxylic acid C=O (also acid "OH").
Typology: Study notes
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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
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)
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.
Example Calculation
δb = 5.2 + (-0.6) = 4. actual = 4.6 (J = 6, 1.6 Hz)
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
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"
meta ortho
para
meta (^) ortho
Example Calculation
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
3
(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
3
3
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
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
alcohols
δ 1 - 5 ppm
phenol and enol protons
δ 7 - 15 ppm
amines
δ 1 - 2 ppm
carboxylic acids
δ 10 - 12 ppm
amides
δ 1 - 6 ppm
∆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 )
∆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)
∆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)
N + 1 rule (N = # neighbors)
N + 1 rule (N = # neighbors)
perturbation(s) by neighbor proton(s)
J (Hz)
J (Hz) J (Hz) J (Hz)
J1a