Shoolery rule
According to Shoolery's rule , named after James Nelson Shoolery , the chemical shift δ of methylene groups in NMR spectroscopy can be estimated to a good approximation with a so-called increment system based on the type of the two substituents A and B (A – CH 2 –B) become.
The increments S are purely empirical parameters and have been tabulated for many different substituents (selection):
| Substituent | S / ppm |
|---|---|
| -CH 3 | 0.47 |
| –COOR | 1.55 |
| –COR | 1.70 |
| -C 6 H 5 | 1.83 |
| –SR | 1.64 |
| –I | 1.82 |
| –Br | 2.33 |
| –OR | 2.36 |
| -Cl | 2.53 |
| -OH | 2.56 |
| –OCOR | 3.13 |
The system can also be transferred to methine protons (CH group with three substituents); the increments in this modified increment system are then the same for methylene and methine protons. Such systems have also been established for protons on C = C double bonds and benzene rings , but the incremental values there depend on the relative position of the substituents (cis, trans, gem, or ortho, meta, para).
literature
- Horst Friebolin: One and two-dimensional NMR spectroscopy . 3. Edition. Wiley-VCH, Weinheim 1999, ISBN 3-527-29514-3 , pp. 141 f .