Thanks to Kathleen Gallagher for the following reference which
puts the bare proton at 31 ppm (delta). A. Carrington, A.D. McLachlan,
Introduction To Magnetic Resonance, Harper and Row, NY, 1967. It also
puts the hydrogen atom at 13 ppm.
Thanks also to Stephanie Mabry for doing the calculation from a
different point of view and for recognizing the 2001 IUPAC NMR
recommendations use the older 1986 CODATA proton gyromagnetic ratio.
My calculated value of about 30 ppm uses the 1998 CODATA values
for gyromagnetic ratios (proton and "shielded proton") which are given on
the NIST web page.
Thanks again,
Ed Waali
*********************************************
At 02:38 PM 5/2/2002 -0600, you wrote:
>NMR Folks,
>
>Does anyone know what the chemical shift of a bare proton would be on the
>ppm scale? I would like this number for my organic NMR interpretation course.
>A NIST web page gives the gyromagnetic ratios (units =10^8 rad s-1 T-1) of
>the proton (2.67522212) and the "shielded proton" (2.67515341). I believe
>the "shielded proton" is that of water at 25 deg. Since these numbers
>differ by 25.7 ppm and since the chemical shift of water is about 4.5 ppm,
>can I estimate the chemical shift of a bare proton to be about 30.2 ppm or
>am I making some fundamental physics mistake?
>The matter is confused by the IUPAC recommendations of last year where TMS
>was continued at the standard (of course) but a gyromagnetic ratio
>of 2.67522128 was given. If this is for TMS, I'm really confused
>because it would place TMS very close to the bare proton.
>Thanks for any help you might give.
>
>Ed Waali
>
>******************************************************************
>Edward E. Waali
>Department of Chemistry
>University of Montana
>Missoula, MT 59812
>
>Voice: (406) 243-4992
>FAX: (406) 243-4227
>E-mail: waali_at_selway.umt.edu
>
>******************************************************************
Received on Tue May 07 2002 - 16:19:54 MST