This document discusses NMR problem solving and spectroscopy. It addresses questions about determining the number of signals expected in 1H NMR, 19F NMR, and other NMR spectra based on equivalent protons, equivalent fluorines, and spin-spin coupling. It also considers how NMR spectra would appear for specific compounds with different nuclei such as 13C, 31P, 11B, 19F, and taking into account coupling and chemical shifts.

1. NMR Problem solving
Dr. Chris, UP Feb 2016

2. Chemical Shift δ

3. equivalent protons
Protons that can be transferred to another one by
mirror or rotation are equivalent
=> They have the same δ and do not couple

4. How many signals ?

6. How many 19F signals ?

8. http://www.rsc.org/images/18_Solving_Inorganic_Spectroscopic_Problems_tcm18-29994.pdf

9. equivalent F

10. t

11. Which F-NMR signals would we expect ?
Replace by C6H5
here

12. a
a
b
c
a
b
We would expect a broadened triplet for each of the
equatorial flourines

13. Questions
How would the 13C NMR spectrum of:
CH3 – CH2 – CH - CH3
|
Br
look like with and without 1H-13C coupling ?
Step 1: identify how many different C atoms ?
Step 2: estimate chemical shift
Step 3: estimate coupling to adjacent protons.

15. How would the spectrum look like for
1H NMR
19F NMR
31P NMR
P-H coupling is bigger than F-H
P-F - “ -
P-F - “ - P-H
How is the 1H spectrum of pure 13C- CH4 ?
- “ - BH4
- ?
- “ - 11B - “ - ?
19F spectrum of TiF4L2 cis and trans ?

16. How is the 19F NMR of ClF5 ?