This document discusses 13C NMR spectroscopy. It explains that 13C NMR can be used to determine the number of non-equivalent carbon atoms in a compound and identify carbon types like carbonyl, methylene, aromatic. The chemical shifts of carbonyl, nitrile and oxime carbons are spread over a wide range from 0-240 ppm. 13C NMR spectroscopy has applications in structure elucidation, detection of functional groups, identification of structural isomers, and metabolic studies. It is useful as a complementary technique to 1H NMR spectroscopy.

1. TOPIC:CHEMICAL
SHIFTS OF
CARBONYL,NITRILE
AND OXIME CARBONS
Paper-4
Unit-4
Sem-4
-sana shaikh
The institute of science ,mumbai.

2. What is 13C N.M.R ? WHY DO WE
NEED IT ?
■ Proton NMR used for study of number of nonequivalent proton present in
unknown compound.
■ Carbon NMR can used to determine the number of non- equivalent carbons
and to identify the types of carbon atoms(methyl, methylene, aromatic,
carbonyl….) which may present in compound.
■ 13C signals are spread over a much wider range than 1H signals making it
easier to identify & count individual nuclei.

3. The NMR ACTIVE NUCLEI INCLUDES.1H ,13C,15N,19F AND
31P .
WHICH HAVE NUCLEAR SPIN OF 1/2

5. DIFFERENCE BETWEEN H-N.M.R AND 13C N.M.R
.1. It is study of spin changes of proton
nuclei
. 1. It is study of spin changes of carbon
nuclei.
2. Chemical shift range is 0-14 ppm 2. Chemical shift range is 0-240 ppm
3. Continuous wave method is used 3. Fourier transform Technique is used
4.slow process 4.Very fast process
5 Coupling constant range is 0-15Hz. 5. Coupling constant range is 125-250Hz.
6.Solvent peak is not observed 6.Solvent peak is observed.
7.Area under the peak is considered 7.Area under the peak is not considered
8. TMS peak is singlet 8.TMS peak is quartet.
9.Effect of substituent on adjacent carbon
atom can varies chemical shift.
9. Effect of substitute on adjacent carbon atom
cannot varies chemical shift.

6. 13C Chemical Shifts.
■ 13C Chemical Shifts are measured in ppm (δ) from the carbons of TMS.
■ The correlation chart is here divided into sections
■ 1) the saturated carbon atom which appear at Upfield,nearest to TMS(8-
60ppm).
■ 2) effect of electronegative atom(40-80ppm)
■ 3) Alkenes and aromatic carbon atom(100-170)
■ 4) It contain carbonyl carbon bond. which appear at Downfield value(155-
200ppm).

8. 13C INTERPRETATION.
■ Count how many lines- how many types of carbons
■ Symmetry duplicates give same line- if there are more carbons in your
spectrum – symmetry
■ Check chemical shift window
■ Check splitting pattern
■ Signal height size
■ 13C NMR spectroscopy provides information about:
■ The number of nonequivalent carbons atoms in a molecule
■ The electronic environment of each carbon
■ How many protons are bonded to each carbon

17. Applications.
■ Identification of structural isomers
■ Detection of hydrogen bonding
■ Detection of aromaticity Distinction between Cis-trans isomers and conformers
■ Detection of electronegative atoms or group
■ Detection of some double bond character due to resonance Industrial
applications in solids Metabolic studies
■ Metabolic studies on human
■ 1. Brain function
■ 2. Glucose metabolism in liver
■ 3. Glucose metabolism in muscle
■ 4. Determination of degree of unsaturation of fatty acids in adipose tissue
■ 5. Characteristic of body fluids and isolated tissues
■ 6. In diseased state .

18. APPLICATIONS .
■ Structure elucidation is most common application of 13C spectroscopy PMR &
CMR are often employed as complementary techniques.
■ Although the order of accuracy achieved by 13C NMR was a low relative to an
high performance liquid chromatography technique, it was concluded that
quantitative analysis by 13C NMR had significant potential in pharmaceutical
analysis.
■ It is also used in the investigation of bio synthetic path ways, dynamic
properties of molecules detection and identification of labeled sites may be
accomplished by CMR directly or by examination of 13C 1H satellite signals.
Example cephalosporin-C