Magnetic Susceptibility and Unpaired electrons

AI Thread Summary
The discussion focuses on calculating the magnetic susceptibility (XM) of Mn(acac)3 to determine the number of unpaired electrons using the Evans Method. The participant calculated XM as 4179.1878 but expressed uncertainty about its accuracy, particularly regarding the magnetic susceptibility of Mn(III) and the contributions from ligands. They noted confusion about the frequency difference calculation and the conversion from ppm to Hz. After realizing the need to multiply the ppm value by the NMR frequency, they indicated this might resolve their issues. The thread highlights the importance of careful unit conversion and accurate data for reliable results in magnetic susceptibility calculations.
ReidMerrill
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Homework Statement


I'm am trying to find out the magnetic susceptibility,XM in order to calculate the number of unpaired electrons in Mn(acac)3 via the Evans Method

Homework Equations


XM = (477) Δv/(Qv1C)
XM= X'm+ XM(metal)+ XM (ligands)
Where X'M is the magnetic susceptibilty of just the unpaired electrons.
Δv is the frequency difference between the two chloroform peaks, 648.2 MHz (7.2722 ppm-5.6517 ppm)*400 MHz
Q=2 because a superconducting NMR was used
v1 is the frequency of the NMR, 400MHz
and c is the molarity of the solution used, 0.0948M
X'MT=(1/8)n(n+2) where n is number of unpaired electrons

The Attempt at a Solution


The XM I calculated is 4179.1878. I have nothing to base the accuracy of this off of.
the XM (metal) = 511. THis was for elemental Mn. I couldn't find anything for Mn(III) so this might be the problem. And from the lab manual the XM(ligands) is 3*52
Solving for X'M I got 3512.1878
This gives an unpaired electron count of of nearly 3,000 so this cannot be correct. Any help is greatly appreciated.
 
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Δν > ν1? Looks like you multiplied 1.6205*400. What about the "ppm"?
 
mjc123 said:
Δν > ν1? Looks like you multiplied 1.6205*400. What about the "ppm"?
1.6205 is the ppm. That's what the lab manual says to do.

EDIT: I see. the ppm x 400 MHz= Hz. I wasn't reading carefully. I'll see if this fixes things
 

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