127Iodine NMR


Safety note: Some of the materials mentioned here are very dangerous. Ask a qualified chemist for advice before handling them. Qualified chemists should check the relevant safety literature before handling or giving advice about unfamiliar substances. NMR solvents are toxic and most are flammable. Specifically, iodide is toxic in large doses. Other oxidation states are more toxic: wear protective gloves.


127Iodine is a medium sensitivity nucleus which yields extremely broad lines in symmetrical environments and is unobservable by high resolution NMR in asymmetrical environments. It has a very wide chemical shift range. It can be used to detect the presence of iodine and its chemical environment.

Each type of signal has a characteristic chemical shift range.

Moiety

Chemical shift (ppm)

I-

-100 to 200

IO4-

4000 to 4100

 

Properties of 127I

Spina

5/2

 

Pulse sequence

 Basic

 

Standard

Chemical shift (ppm)b

Frequency (1H=1)bc

Line width (Hz)bd

T1 (s)bd

KI (1M) in D2O

0

0.2000775

1926

0.000135

 

Chemical shift range (ppm)e

Minimum (ppm)

Maximum (ppm)

4200

-100

4100

 

Sensitivity

At natural abundance

 100%

Enriched

Relative to 1H

9.34 x 10-2

9.34 x 10-2

Relative to 13Cf

531

531

aSpin half nuclei generally yield sharp signals. Nuclei with higher spins are quadrupolar. The broadness of their signals increases as a function of the quadrupolar moment and asymmetry of environment. This broadening, especially in asymmetric environments, often yields signals that are too wide to be detected with a high-resolution NMR spectrometer. These effects are not related to broadening caused by paramagnetism that may also make signals unobservable. bAt 298 K. c0 ppm for this nucleus relative to the TMS proton signal = 1. dAt 9.3981 T (400.13 MHz for 1H resonance) in CDCl3. eThe chemical shift range is for the vast majority of compounds. Occasionally signals will be observed outside this range. fAt natural abundance: 1.108%.


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Revised: December 21, 1997 by Roy Hoffman
NMR laboratory manager, Department of Organic Chemistry, The Hebrew University of Jerusalem, Jerusalem, Israel 91904,
Tel. (972) 2 6585327, Fax (972) 2 6585345, Email
roy@shum.cc.huji.ac.il

Copyright (C) Roy Hoffman, The Hebrew University of Jerusalem 1996-7.