Interpretting C-NMR
Spectra
The following information is to be gained from a typical broadband
decoupled 13C NMR spectrum:
How many Indicated by how many signals there are in
types of C ? the spectra
What types Indicated by the chemical shift of each
of C ?
signal
http://www.chem.ucalgary.ca/courses/351/Carey/Ch13/ch13-cnmr-2.html
typical chemical shifts in C-13 NMR spectra
carbon environment
C=O (in ketones)
chemical shift (ppm)
205 - 220
C=O (in aldehydes)
190 - 200
C=O (in acids and esters)
170 - 185
C in aromatic rings
125 - 150
C=C (in alkenes)
115 - 140
RCH2OH
50 - 65
RCH2Cl
40 - 45
RCH2NH2
37 - 45
R3CH
25 - 35
CH3CO-
20 - 30
R2CH2
16 - 25
RCH3
10 - 15
Nuclear Magnetic Resonance Spectroscopy
13C
NMR—Number of Signals
www.daltonstate.edu/faculty/rcollison/McMurry-Chapter%2013%20.ppt
carbon
environment
chemical shift
(ppm)
C-C
0 - 50
C-O
50 - 100
C=C
100 - 150
C=O
150 - 200
http://www.chemguide.co.uk/analysis/nmr/interpretc13.html#top
13C-NMR
http://www.chem.ucalgary.ca/courses/351/Carey/Ch13/ch13-cnmr-2.html
CH3
CH-O
CH3
C=O (Ester)
CH2-C=O
http://www.chemguide.co.uk/analysis/nmr/backgroundc13.html#top
?
There are four peaks and four carbons
The peak at just over 50 must be a carbon attached to an oxygen by a single bond.
The two peaks around 130 must be the two carbons at either end of a carbon-carbon
double bond.
The peak at just less than 170 is the carbon in a carbon-oxygen double bond.
http://www.chemguide.co.uk/analysis/nmr/interpretc13.html#top
C-13 NMR
CH2-O
CH3
http://www.chemguide.co.uk/analysis/nmr/backgroundc13.html#top
Thare are four alcohols with the molecular formula C4H10O
Which one produced the 13C- NMR spectrum below?
http://www.chemguide.co.uk/analysis/nmr/interpretc13.html#top
This follows on from Example 2, and also involves an isomer of C4H10O but which
isn't an alcohol. Its C-13 NMR spectrum is below. Work out what its structure is.
CH3CH2OCH2CH3
?
http://www.chemguide.co.uk/analysis/nmr/interpretc13.html#top
www.daltonstate.edu/faculty/rcollison/McMurry-Chapter%2013%20.ppt
http://www.chem.ucalgary.ca/courses/351/Carey/Ch13/ch13-cnmr-2.html
The presence of an electronegative atom such as oxygen tends to move the
chemical shift 65 – 90 ppm
http://www.chem.uic.edu/web1/ocol/spec/C13-1.htm
carbons adjacent to halogens tend to have chemical shifts in the 30 – 50
ppm
The nitrile carbon is significantly shielding and adjacent carbons tend to
occur in the 20 - 25 region
Alkene carbons tend to have chemical shifts in the range
110 - 140
http://www.chem.uic.edu/web1/ocol/spec/C13-1.htm
Alkyne carbons occur in the region
65 -85
Carbonyls are the most highly deshielded carbons which are typically
encountered.
Typical chemical shifts occur in the region 170 - 210 with esters, carboxylic
acids and amides at the low end, and simple ketones and aldehydes at the
high end of the range
http://www.chem.uic.edu/web1/ocol/spec/C13-1.htm
Aromatic carbons have chemical shifts in the range
120 - 140
http://www.chem.uic.edu/web1/ocol/spec/C13-1.htm
13 C
C,CH, CH2,CH3
DEPT 90
-CH
DEPT 135
-CH3, CH (del mismo lado)
-CH2 (del lado opuesto)
13C-NMR: (a) proton decoupled and (b) DEPT