This document provides an introduction and overview of 13C-NMR spectroscopy principles. It explains that 13C-NMR is used to determine the types of carbon atoms in a molecule by taking advantage of the spin properties of the rare 13C isotope. Specifically, it notes that 13C has a nuclear spin of 1/2, accounting for only 1.1% of naturally occurring carbon, and its signals are spread over a wider range and easier to identify than proton NMR. The document also briefly outlines some key aspects of 13C NMR experiments, such as carbon chemical shift ranges and proton decoupling.

1. Nuclear Magnetic Double
Resonance, Brief outline
of Principles of 13C-NMR
Presented by :
Soma Ghosh
M.Pharm (1st Year ) Pharmaceutical Chemistry
Roll No- 36520123004
Anand College of Education

2. INTRODUCTION
⚫Nuclear magnetic resonance Spectroscopy is a
powerful analytical technique used to
charecterise organic molecule by identifying
Carbon-Hydrogen frameworks with in molecule.
⚫Two types of NMR Spectroscopy are used
to charecterise organic structure :-
⚫H-1 NMR :-Todetermine the type and number of
H atoms in a molecule.
⚫C-13 NMR:- Used to determine type of carbon atoms
in the molecule.

3. PRINCIPLE
⚫Nuclear magnetic resonance concern the magnetic
properties of certain atomic nuclei.
⚫It concern the atom having spin quantum number.
⚫ C-12 nucleus is not magnetic active because ;
C-12:- Proton 6 ,Neutron 6
Nuclear spin (I)=0
C-13:-
Proton6,Neutron7
Nuclear spin (I)=1/2
⚫Relatively new technique as compared to proton NMR.

4. ⚫C-13 NMR
⚫C-12 have no magnetic spin and produce no NMR signal.
⚫C-13 have magnetic spin(I)=1/2
⚫C-13 account for only 1.1%of naturally occurring carbon.
No coupling between C-13and C.
 C-13 have weak signal.
 C-13 have strong coupling with H.
 C-13 have weak coupling with C.
⚫C-13 has only about 1.1% natural abundance (of carbon
atoms).
⚫C-12 does not exhibit NMR behavior.

5. ⚫As a result, C is about 400 times less sensitive than H
nucleus to the NMR phenomena.
⚫Chemical shift range is normally 0 to 220ppm.
⚫Normal C-13 Spectra are “broadband, proton
decoupled”so the peaks show as single lines.
⚫Number of peak indicates the number of type of
Carbon atoms.

6. •WHY C-13 NMR REQUIRED
⚫Carbon NMR can used to determine the number of non-
equivalent carbon and no identify the types of carbon atoms
(methyl,methylene,aromatic ,carbonyl
)which may present in compound.
⚫C13 Signal are spread over a much wider range than proton
signal making it easier to identify and counts individual
nuclei.

7. •REFERENCES
⚫McCash M. Elain and Banwell N.Colen “fundamental
of molecular spectroscopy,”4th edittion,
TataMcGrawHill publishing company LTD.New
Delhi.page no-234-240.
⚫Chatwal R. Gurdeep and Anand K. Sham,”Intrumental
method of chemical analysis,”Himalaya publishing
house mumbai, Delhi. page no. 2.231.
⚫H. Kour by Spectroscopy ,12th eddi. Pragati
publication,page no. 415-424.

8. Thank you