13C NMR Flashcards
1
Q
What is the relative abundance of 13C?
A
1%
2
Q
How much does double the scans improve the signal:noise ratio by?
A
2^1/2
3
Q
What are the factors affecting the sensitivity?
A
Imperfect relaxation of electrons between readings, relax through oscillating dipoles from H
4
Q
Why is there no 13C-13C coupling?
A
The chance of two neighbouring 13C atoms is very low
5
Q
Why is there no 13C-H coupling?
A
Removed by irradiation
6
Q
Justify the appearance of the solvent peak
A
There is still coupling between other 1/2 spin nuclei such as F and Cl
7
Q
What does DEPT135 show?
A
Whether a particular environment is C/CH/CH2/CH3
8
Q
What happens to different environments in DEPT135?
A
CH/CH3 go up, CH2 goes down and C disappears
