Kennesaw State University Molecular Ion Spectroscopy Problems Worksheet

Problem 14: (C6H11NO2)Molecular ion =
129 m/z
1084 cm-1
2248 cm-1
Problem 14: (C6H11NO2)
6H
2H, quartet
2H, triplet
1H, triplet
6
5
4
3
PPM
2
1
0
Problem #: ___________________________
Molecular Formula: _________________________
Degree of Unsaturation: ____________________
1. Analysis of infrared (IR) spectrum:
Observations (absorptions in cm-1)
Inferences
2. Analysis of 13C-NMR spectrum:
Observations
Inferences
3. Analysis of proton-NMR spectrum: (Each signal must be analyzed to generate a possible
fragment.)
Observations
Inferences
4. Final structure of the compound along with assignment of carbon and proton chemical
shifts.
FTIR
NEAT
100
90
80
70
60
50
40
30
1614.1
20
1515.8
1035.6
1735.6
1249.6
10
3750
3500
3250
3000
2750
2500
2250
2000
1750
Wavenumbers (cm-1)
© 2020, Sigma-Aldrich Co.
ALL RIGHTS RESERVED
1500
1250
1172.5
1000
750
500
75 MHz ¹³C NMR
In CDCl3
solvent
220
200
180
160
140
120
100
80
© 2020, Sigma-Aldrich Co.
ALL RIGHTS RESERVED
60
40
20
0
300 MHz ¹H NMR
In CDCl3
3H
2.6
7.5
7.4
7.3
7.2
7.1
7.0
6.9
© 2020, Sigma-Aldrich Co.
6.8
2.4
2.2
2.0
6.7
1.8
1.6
1.4
© 2020, Sigma-Aldrich Co.
1.2
3H, J = 7.5 Hz
2H
2H, J = 7.5 Hz
2H, J = 8.7 Hz
8
2H, J = 8.7 Hz
7
6
5
4
3
© 2020, Sigma-Aldrich Co.
ALL RIGHTS RESERVED
2
1
0
1.0
0.8
Problem #: ___________________________
Molecular Formula: _________________________
Degree of Unsaturation: ____________________
1. Analysis of infrared (IR) spectrum:
Observations (absorptions in cm-1)
Inferences
2. Analysis of 13C-NMR spectrum:
Observations
Inferences
3. Analysis of proton-NMR spectrum: (Each signal must be analyzed to generate a possible
fragment.)
Observations
Inferences
4. Final structure of the compound along with assignment of carbon and proton chemical
shifts.
 
Page  
1  
CHEM  3362  –  Spectroscopy  Data  Tables  
 
Characteristic Infrared Absorptions
 
Page  
2  
CHEM  3362  –  Spectroscopy  Data  Tables  
 
Characteristic Ranges for C13 and H-NMR Signals
Beauchamp
Spectroscopy Tables
3
units = cm-1
4000
2500
3000
3500
sp C-H
stretch
1700
2000
sp3 C-H
stretch
C C
thiol S-H
stretch
sp2 C-H
stretch
1500 1400 1300 1200 1100 1000 900 800 700
C=O
stretch
aldehyde C-H
stretch
geminal
acyl C-O
phenol C-O
tri
aromatic sp2 C-H
bend
mono
N-H bend
ortho
2o N-H
stretch
nitro
meta
nitro
para
3000
2500
1700
2000
1500 1400 1300 1200 1100 1000 900
expansion of alkene & aromatic sp2 C-H bend region (units = cm-1)
700
600
800
900
mono
cis
trans
C=C stretch
aromatic
1o N-H2
stretch
1000
mono
alkoxy C-O
carboxylic acid O-H
stretch
3500
sp C-H
bend
C=C stretch
alkene
alcohol O-H
stretch
4000
alkene sp2 C-H
bend
3
C=N
stretch
C N
600 500
800 700
600 500
500
mono
cis
alkene sp2 C-H
bend
trans
geminal
tri
mono
mono
aromatic sp2 C-H
bend
ortho
meta
meta
meta
para
1800
1750
expansion of carbonyl (C=O) stretch region (units = cm-1)
1700
Saturated C=O lies at
higher cm-1
C=O in samll rings
lies at higher cm-1
1650
carboxylic acid C=O (also acid “OH”)
ester C=O (also acyl C-O and alkoxy C-O)
aldehyde C=O (also aldehyde C-H)
ketone C=O (nothing special)
acid chloride C=O (high C=O, 1 peak)
anhydride C=O
anhydride C=O (high C=O, 2 peaks)
Z:\classes\spectroscopy\all spectra tables for web.DOC
amide C=O (low C=O, amide N-H)
1600
Conjugated C=O
lies at lower cm-1
Beauchamp
Spectroscopy Tables
4
IR Flowchart to determine functional groups in a compound (all values in cm-1).
IR Spectrum
has C=O band
(1650-1800 cm-1)
very strong
does not have
C=O band
C
C
C
N
aldehydes
O
1725-1740 (saturated)
1660-1700 (unsaturated)
C
sometimes lost
2860-2800
in sp3 CH peaks
2760-2700
aldehyde C-H
(both weak)
ketones
1710-1720 (saturated)
1680-1700 (unsaturated)
1715-1810 (rings: higher
in small rings)
C
esters – rule of 3
O
1735-1750 (saturated)
1715-1740 (unsaturated)
1735-1820 (higher in small rings)
C
N
a little lower
when conjugated
2850-3000
1460 & 1380
sp3 C-H bend
C
not useful
C
alkenes
sp2 C-H stretch
3000-3100
2150
(variable intensity)
not present or weak when symmetrically
substituted, a little lower when conjugated
C
C
650-1000
(see table for
spectral patterns)
sp C-H stretch
sp C-H bend
3300
sharp, strong
sp2 C-H bend
C
1600-1660
weak or not present
C
aromatics
sp2 C-H stretch
3050-3150
690-900 (see table),
overtone patterns
between 1660-2000
620
sp2 C-H bend
acyl
1150-1350 (acyl, strong)
O
alkoxy
C
C
alkanes
sp3 C-H stretch
alkynes
O
C
nitriles
≈ 2250
sharp, stronger
than alkynes,
(1000-1150, alkoxy, medium)
O
acids
O
1700-1730 (saturated)
1715-1740 (unsaturated)
1680-1700 (higher in small rings)
C
acyl
C
O
1210-1320 (acyl, strong)
H
2400-3400, very broad
(overlaps C-H stretch)
acid
O
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).
1600 & 1480
can be weak
C
alcohols
alcohol
O
3600-3500
H
O
1000-1260
(3o > 2o > 1o)
H
≈ 2550 (weak)
(easy to overlook)
alkoxy
C
thiols
thiol
Alkene sp2 C-H bending patterns
amides
S
amines
O
1630-1680 (saturated)
1745 (in 4 atom ring)
C
H
N
o
N
1
C
H
N
2o
H
3350 & 3180, two bands
for 1o amides,
one band for 2o amides,
H stronger than in amines, extra
overtone sometimes at 3100
N-H bend, 1550-1640,
stronger in amides than amines
acid chlorides
1800 (saturated)
1770 (unsaturated)
O
C
Inductive pull of Cl increases the
electron density between C and O.
anhydrides
O
1760 & 1820 (saturated)
1725-1785 (unsaturated)
two strong bands
C
monosubstituted alkene (985-1000, 900-920)
geminal disubstituted (960-990)
cis disubstituted (675-730)
trans disubstituted (880-900)
trisubstituted (790-840)
tetrasubstituted (none, no sp2 C-H)
Aromatic sp2 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)
H
N
1o
H
2o
N
H
N-H bend, 1550-1640,
stronger in amides than amines
N
C
1000-1350
(uncertain)
ethers
alkoxy
C
1120 (alphatic)
1040 & 1250 (aromatic)
O
nitro compounds
O
1500-1600, asymmetric (strong)
1300-1390, symmetric (medium)
N
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.
3300 – 3500, two bands
for 1o amines, one band
o
H for 2 amines, weaker
than in amides,
N
O
carbon-halogen bonds
C
X
acyl
C
O
1150-1350 (acyl, strong)
X = F, Cl, Br, I
Z:\classes\spectroscopy\all spectra tables for web.DOC
usually not
very useful
Beauchamp
Spectroscopy Tables
5
Typical 1H and 13C NMR chemical shift values.
deshielding side = less electron rich
(inductive & resonance)
shielding side = more electron rich
(inductive & resonance)
typical proton chemical shifts
amine N-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.
2
alcohol
O
1
H
5
1
amide N-H
6
1
S C H
thiols, sulfides
2.5
N
3
7+
1.5
3+
4
thiol
SH
2
1.5 1.3
epoxide C-H
10
10
9
8+
9
8
10
7
PPM
alcohols
ethers
esters
C
5+
6
2
2
3
4
halogen
0.5
2
typical carbon-13 chemical shifts
1
15
95
C
R
N C
R
ketones
no H
amines, amides
with & without H
180
220+
0
F ≈ 80-95
Cl ≈ 45-70
Br ≈ 35-65
I ≈ 15-45
C
with & without H
O
simple sp3 C-H
CH > CH2 > CH3
H
3.3 3
5
6
2.5
3.5
H
O C
aromatic C-H
aldehyde C-H
11
2.5
benzylic C-H
carbonyl alpha C-H
alkene C-H
12
2.3
allylic C-H
5
12
C H
amines
3.0
X C H
X = F,Cl,Br,I
carboxylic acid O-H
2.0
50
O
O
30
C
R
180
C C
with & without H
N C
no H
90+
220
200
S
C
thiols, sulfides
with & without H
160
O
C
alcohols,
ethers, esters
40
20
with & without H
H
C
aldehydes
with H
240
40
110
125
C
210
60
70-
O
R
epoxides
with & without H
X
carboxylic acids
anhydrides
esters
amides
acid chlorides
no H
C
80
C
+
50
with & without H
180
180
160+
160
Z:\classes\spectroscopy\all spectra tables for web.DOC
100-
140 PPM 120
100
simple sp3 carbon
C > CH > CH2 > CH3
with & without H
60+
80
60
0
40
20
0