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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
C C C C
C O
C C (^) C N
C O
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
C O
C N
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
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 1600- weak or not present
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.
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
7 +^4
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
1. δ (CH 3 ) = 0.9 + 2.8 = 3.
actual = 3.
2. δ (2) = 7.3 + (-0.5) ortho + (-0.1) para = 6.
actual = 6.
3. δ (3) = 7.3 + (-0.2) ortho + (-0.4) para = 6.
actual = 7.
4. δ (CH 2 ) = 1.2 + (0.8)α + (1.4)α = 3.
actual = 3.
5. δ (5) = 5.2 + (0.7) gem = 5.
actual = 5.
6. δ (6) = 5.2 + (-0.2) trans = 5.
actual = 5.
7. δ (7) = 5.2 + (-0.2) cis = 5.
actual = 5.
- 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
- 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
∆E 2
∆E 3
J1a
J1b J1b two equal energy two neighbor protons are like populations here two small magnets that can be 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
∆E 2
∆E 3
J1a
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
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
Splitting patterns when the N+1 rule works (common, but not always true)
C C
H
C
H 2
C
H
C CH 3
H H
C CH
H
CH
t, J= I=1H N=
d, J= I=1H N=
q, J= I=1H N=
C CH
H
CH
CH
C CH 2
H
CH
C
H
s, J=none I=1H N=
δ = calc or exp
N = 0 N = 2 N = 3
C CH 3
H
CH
qnt, J= I=1H N=
C CH 2
H
CH
CH
N = 4
C CH 3
H
CH 2
sex, J= I=1H N=
C CH 2
H
CH
CH 2
N = 5
C CH 3
H
CH 3
sep, J= I=1H N=
C CH 2
H
H 2 C
CH 2
N = 6
C CH 3
H
CH
CH 3
oct, J= I=1H N=
N = 7
C CH 2
H
CH 2
C CH 3
H
CH
CH
C CH 3
H
CH
H 2 C
C CH 3
H
H 2 C
CH 2
C CH 3
H
H 2 C
CH 3
non, J= I=1H N=
N = 8 Pascal's triangle = coefficients of variable terms in binomial expansion (x + y)n^ , n = integer
N = 1
δ = calc or exp δ = calc or exp δ^ = calc or exp
δ = calc or exp δ = calc or exp
δ = calc or exp δ^ = calc or exp
δ = calc or exp
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 (% edge peak shown)
= group without any coupled proton(s)
d 0 - 30 ppm
Simple alkane carbons
CH 3
CH (^2) CH
d (^) 20 - 40 ppm d (^) 30 - 50 ppm
d 50 - 60 ppm
sp 3 carbon next to oxygen
CH 3 O
d (^) 55 - 80 ppm d (^) 60 - 80 ppm
d (^) 10 - 50 ppm
sp 3 carbon next to nitrogen
CH 3 N
d (^) 35 - 55 ppm d (^) 50 - 70 ppm
sp 3 carbon next to
bromine or chlorine
(X = Cl, Br) d^ 25 - 50 ppm^ d (^) 60 - 80 ppm
sp carbon (alkynes) C^ C sp carbon (nitriles) C N
δ 70 - 90 ppm δ 110 - 125 ppm
sp 2 carbon (alkenes and aromatics)
simple sp 2 carbon resonance donation moves δ lower, resonance withdrawal moves δ higher
sp 2 carbon attached to an electronegative atom (X = oxygen, nitrogen, halogen) or Cβ carbon conjugated with a carbonyl group
C H C X
δ 100 - 140 ppm^ δ^ 140 - 160^
ppm
C
O
X
carboxyl carbons (acids, esters, amides)
δ 160 - 180 ppm
C
O
H
δ 180 - 210 ppm
C
O
R
aldehyde carbons, lower values when conjugated
δ 180 - 220 ppm
C
ketone carbons, lower values when conjugated
d (^) 30 - 60 ppm
C H C^ X
(q) (^) (t) (d) (^) (s)
C O
d 70 - 90 ppm (q) (t) (d) (s)
C N
d (^) 50 - 70 ppm (s)
C X
d (^) 60 - 80 ppm (s)
(q) (t)^ (d)
(t) (d)
(s) (d) (s)
Similar chemical shift information presented in a different format. Remember, proton decoupled carbons appear as singlets. When carbons are coupled to their hydrogens, carbons follow the N+1 rule. Methyls = q, methylenes = t, methines = d, and carbons without hydrogen appear as singlets = s. DEPT provides the same information. Carbon chemical shifts are spread out over a larger range than proton chemical shifts (they are more dispersed), so it is less likely that two different carbon shifts will fall on top of one another. The relative positions of various types of proton and carbon shifts have many parallel trends (shielded protons tend to be on shielded carbons, etc.)
CH 2 O (^) CH O
CH 2 N (^) CH N
CH 2 X (^) CH X
Calculations of alkane 13 C chemical shifts not listed above.
sp 3 Carbon Chemical Shift Calculations
Calculations for sp 3 carbon 13 C chemical shifts of functionalized carbon skeletons can be performed starting
from the actual shifts found in the corresponding alkane skeleton, and introducing corrections factors based on the
functionality present in the molecule. This assumes that the alkane 13 C shifts are available, which is why several
examples are provided below.
Examples of C (^) n alkanes as possible starting points for calculation 13 C shifts in ppm.
The calculated carbon atom is:
primary secondary tertiary quaternary
The attached Cα carbons are:
primary secondary (^) tertiary quaternary
0 0 0 -1.
0 0 -3. -8.
-1. -2. -9. -15.
-3. -7. -15. -25.
CH 4 -2.3 5.9 15.
C 2 C^3 C^4 25.
14.1 (^) 31.
30.2 11.
C (^5) 32.
36.3 29.3 18.
C 6
22.9 29.
29.734.439.
C 7
29.8 14.
27.0 (^) 27.
22.9 29.
C 8
39.2 32.
27.2 22.
29.6 19.
11.5 14.
20.3 32.
29.8 32.2^ 29.
22.9 29.
C (^9) C 10
(^13) C shifts for various carbon alkane skeletons - useful starting points for calculating sp3 carbon chemical shifts
Steric Corrections for sp^3 carbon chemical shift calculations Approximate^13 C shift calculation from scratch.
δ C = -(2) + 9x(# α + # β ) - 2x(# γ ) + steric corrections
1
2 3 4 5 6
C1 = -2 + 9(1+3) - 2(2) + (-3) = 29 (actual = 28.3) C2 = -2 + 9(4+2) - 2(2) + [3x(-1.5)+(-15.0)] = 28 (actual = 34.0) C3 = -2 + 9(3+5) - 0(2) + [(-9.5)+(-15.0)] = 45 (actual = 47.9) C4 = -2 + 9(3+2) - 3(2) + (-9.5) = 27 (actual = 27.2) C5 = -2 + 9(1+2) - 2(2) + (-1) = 20 (actual = 19.5) C6 = -2 + 9(1+2) - 5(2) + (-1) = 14 (actual = 8.5)
F (^70 8) -7 67 5 -
31 10 -5^36 8 -
-7 11 -2 7 11 -
Cl
I
C
O
H
Br
30 0 -3^24 -1^ -
20 10 -4 28 10 -
C
O
CH 3
31 1 -3^26 0 -
C
O
OH
22 2 -3^18 1 -
X is attached to a terminal carbon atom (ppm) X is attached to an internal carbon atom (ppm)
Substituent = X (^) Cα correction (^) Cβ correction Cγ correction Cα correction (^) Cβ correction Cγ correction
X is attached to a terminal carbon atom (ppm) X is attached to an internal carbon atom (ppm) Substituent = X (^) Cα correction (^) Cβ correction (^) Cγ correction Cα correction (^) Cβ correction (^) Cγ correction
C N
C
O
OCH 3
20 2 -3^16 2 -
C
O
NH 2
25 3 -3^19 2 -
3 3 -3^3 3 -
C
O
Cl
33 2 -3^30 2 -
SH (^11 10) -3 12 8 -
SR 22 8 -3 20 6 -
C C
123 ppm starting point for alkene carbon
Additional starting point for calculating 13 C chemical shifts (ppm) of substituted alkenes (just a few possibilities)
Substituent Z 1 Z 2 -H 0 0 -CH 3 13 - -CH 2 CH 3 17 - -CH 2 CH 2 CH 3 16 - -CH(CH 3 ) 2 23 - -C(CH 3 ) 3 26 - -CH 2 Cl 10 - -CH 2 Br 11 - -CH 2 I 14 - -CH 2 OH 14 - -CH=CH 2 14 - -CCH -6 6 -C 6 H 5 12 -
C C C C C C
γ (^) β α α ' (^) β ' γ '
increments for directly attached carbon atoms
123 + correction factors
α = 11 β = 5 γ = -
α ' = - β ' = - γ ' = 2
steric corrections for each pair of cis-α,α ' substituents - for each pair of geminal-α,α substituents - for each pair of geminal-α,α 'substituents 3 if one or more β sutstituents are present 2
C C
Z
2 1 Effect of substituents on alkene^13 C shifts (ppm)
Substituent Z 1 Z 2 -F 24 - -Cl 3 - -Br -9 - -I -38 7 -OCH 3 29 - -O 2 CCH 3 18 - -N(CH 3 ) 2 28 - -NO 2 22 - -CN -15 14 -SCH 2 CH 3 9 - -CHO 15 14 -COCH 3 14 5 -CO 2 H 5 10 -COCl 8 14
δC = 123 ppm + Zi
128 ppm starting point for benzene carbon
Additional starting point for calculating 13 C chemical shifts (ppm) of substituted benzene rings (just a few possibilities)
Substituent 1
2
3
4
Substituent Z 1 Z 2 Z 3 Z (^4) -H 0 0 0 0 -CH 3 9 1 0 - -CH 2 CH 3 12 -1 0 - -CH 2 CH 2 CH 3 10 0 0 - -CH 2 CH 2 CH 2 CH 3 11 0 0 - -CH(CH 3 ) 2 20 -2 0 - -C(CH 3 ) 3 19 -3 0 - -CH 2 F 8 -1 0 0 -CH 2 Cl 9 0 0 0 -CH 2 Br 9 1 0 0 -CH 2 I 11 -1 0 - -CH 2 OH 12 -1 0 - -CH 2 NH 2 15 -1 0 - -CH 2 NO 2 2 2 1 1 -CH 2 CN 2 0 -1 - -CH 2 SH 12 -1 0 - -CH 2 CHO 7 1 0 - -CH 2 COCH 3 6 1 0 - -CH 2 CO 2 H 6 1 0 - -CH 2 =CH 2 13 -3 0 - -CCH -6 4 0 0 -C 6 H 5 8 -1 0 - -F 34 -13 2 - -Cl 5 0 1 2 -Br -5 3 2 - -I -31 9 2 -
Use correction term for carbon atom in relative position to the substituent. Start with 128 ppm.
Substituent Z 1 Z 2 Z 3 Z 4 -OH 29 -13 1 - -OCH 3 34 -14 1 - -OC 6 H 5 28 -11 0 - -NH 2 18 -13 1 - -NHCOCH 3 10 -8 0 - -NHOH 22 -13 -2 - -NHNH 2 23 -16 1 - -N=N-R 22 -6 0 - -NO 37 -8 1 7 -NO 2 20 -5 1 6 -SH 4 1 0 - -SCH 3 10 -2 0 - -S(O)CH 3 18 -5 1 2 -SO 2 CH 3 12 -1 1 5 -SO 2 Cl 16 -2 1 7 -CN -16 3 1 4 -CHO 8 1 0 6 -COCH 3 9 0 0 4 -CO 2 H 2 2 0 5 -CO 2 CH 3 2 1 0 4 -CONH 2 5 -1 0 3 -COCl 11 0 0 - -Li -43 -13 2 3 -MgBr -36 -11 3 4
Starting points for other common ring systems. (ppm). No correction terms included for substituents.
128
126
134
N
naphathalene
pyridine
150
124
136
N H
118
108
O
143
110
S
125
126
pyrrole
furan
thiophene
mass = 39 (R = H) 53 (R = CH 3 ) 67 (R= CH 2 CH 3 )
R
C H
R
mass = 41 (R = H) 55 (R = CH 3 ) 69 (R= CH 2 CH 3 )
mass = 65 (R = H) 79 (R = CH 3 ) 93 (R= CH 2 CH 3 )
R R
mass = 91 (R = H) 105 (R = CH 3 ) 119 (R= CH 2 CH 3 )
CH 3 = 15
CH 3 CH 2 = 29
C 3 H 7 = 43
C 4 H 9 = 57
C 5 H 11 = 71
C 6 H 13 = 85
C H 2
H H
H
R
mass = 27
mass = 42 (R = H) 56 (R = CH 3 ) 70 (R= CH 2 CH 3 )
O C R
mass = 29 (R = H) 43 (R = CH 3 ) 57 (R= CH 2 CH 3 ) 71 (R = C 3 H 7 ) 105 (R = C 6 H 5 )
H 2 N C O
RO C O
mass = 44
Loss of small molecules via elimination reactions.
H 2 O (^) H 2 S CH 3 OH C 2 H 5 OH NH 3 CH 3 CO 2 H HF HCl HBr mass = 18 34 32 46 17 62 20
A sampling of unusual and/or miscellaneous peaks that are commonly seen, (even when they don't make sense).
C R
O
H
CH 2
McLafferty
mass = 44 (R = H) 58 (R = CH 3 ) 72 (R= CH 2 CH 3 ) 86 (R = C 3 H 7 )
R C H 2
R 1
R 2
H O (^) R 2
R 1 variable mass,
(can sometimes see cation on this side too)
Notice! even masses
McLafferty Possibilities
C R
H 2 C
H
CH 2
R C H 2
R 1
R 2
H CH 2
C H 2
R 1
R 2
H C
H
C H 2
R 1
R 2
H N
45 (R = H)
59 (R = CH 3 )
73 (R= CH 2 CH 3 )
mass =
C H 2
R 1
R 2
H
H H
C CH 2
C
H H
C CH 2
N
H
also works for R CH 2
mass = 77
mass = 42 (R = H) 56 (R = CH 3 ) 70 (R= CH 2 CH 3 ) 84 (R = C 3 H 7 )
mass =
R
92 (R = H)
106 (R = CH 3 )
120 (R= CH 2 CH 3 )
134 (R = C 3 H 7 )
mass = 40 (R = H) 54 (R = CH 3 ) 68 (R= CH 2 CH 3 ) 82 (R = C 3 H 7 )
mass = 41 (R = H) 55 (R = CH 3 ) 69 (R= CH 2 CH 3 ) 83 (R = C 3 H 7 )
Similar Patterns
HC
CH 2
R
28 (R = H)
42 (R = CH 3 )
56 (R= CH 2 CH 3 )
70 (R = C 3 H 7 )
mass =
R 2
R 1
R 2
R 1
R 2
R 1
R 2
R 1
