Shoolery's rule

{{distinguish|Shelley's rule}}

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Shoolery's rule, which is named after James Nelson Shoolery, is a good approximation of the chemical shift δ of methylene groups in proton nuclear magnetic resonance. We can calculate shift of the CH₂ protons in a A–CH₂–B structure using the formula

:$\backslash delta\; =\; 0.23\backslash ,\backslash mathrm\{ppm\}\; +\; S\_\backslash mathrm\{A\}\; +\; S\_\backslash mathrm\{B\}$

where 0.23 ppm is the chemical shift of methane and the empirical adjustments {{var|S}} are based on the identities of the A and B groups:

class="wikitable"
class="hintergrundfarbe5" ! Substituent !! S / ppm
–CH3	0.47
–COOR	1.55
–COR	1.70
–C6H5	1.83
–SR	1.64
–I	1.82
–Br	2.33
–OR	2.36
–Cl	2.53
–OH	2.56
–OCOR	3.13

Shoolery's rule is a particular instance of a general class of rules of the form

:$\backslash delta\; =\; b\_0\; +\; \backslash sum\_i\; z\_i$,

with two substituents on methylene resulting in two parameters $S\_A$ and $S\_B$.{{cite journal |last1=Schaller |first1=Renate |last2=Arnold |first2=Cédric |last3=Pretsch |first3=Ernö |title=New parameters for predicting 1H NMR chemical shifts of protons attached to carbon atoms |journal=Analytica Chimica Acta |date=1995-08-18 |volume=312 |issue=1 |pages=95-105 |doi=10.1016/0003-2670(95)00106-A |url=https://www.sciencedirect.com/science/article/abs/pii/000326709500106A |access-date=2024-02-06|url-access=subscription }}