NMR Double Resonance

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