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Lecture #13 02.02.17
126 Ppm CH3
\135 ppm Mlsonlboppm
Oxygen will donate
gThe electrons donated by oxygen can be found anywhere
→along the ring .
goes up field
Positions With sare shielded =D wpfield .
of the 7
Positions with St are deshieldea .
=D downfield .
When you have alot of branches in the carbon , it shifts it downfield .Stoic hindrance .
13C NMR shifts of carbonyl groups
Important about carbonyl groups :
The carbonyl carbon would be moved downfield partly because of the diamagnetic
anisotropy .( electrons moving around ).Also more downfield due to e- Withdrawing group .
To demonstrate the Dolan 'tU Of the bond .
It add groups (4) that can donate electron density to The 5, Then that Will shift it more up field Within the carbonyl
aCan split the carbonyl groups into Two main categories :
Alkyl groups 11 11
can ornate c- c- c-c- +,,Yfgµ
below ZZOPPM means 175 -165 ppm
that they have some sort
to them ,like a double Identifying esters from ketone was hard in Ir ,but
bond or a benzene ring .
in Nmr is easier .
Abovezzoppm means that
there is no corrugation .
Examples of 13C NMA :
noisy baseline due to insensitive method .
Size of The peaks does n't disclose anything .However ,there are three methyl groups that are Three similar methyl
groups so their peak must be taller .
*Quaternary carbons tend to be small .
Can also identity them based on the number of peaks that arise due to symmetry .