Can someone explain directiong of shift for shielding efffect on the 1H NMR?

[monkeyMD]

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Can someone explain the shifting to me?
Thanks!

 

[flodhi1]

Can someone explain the shifting to me?
Thanks!

This belongs in the question and answer section.
Here's how I learned it in lab and was able to memorize it. It might not be the best but makes perfect sense.
So the electrons around the proton create a magnetic field that opposes the applied field during a NMR. Since this reduces the field experienced at the nucleus, the electrons are said to shield the proton. Just imagine electrons like "protecting" the protons it's literally like shielding. However if there is an electron withdrawing group close in proximity then it withdraws electrons. Thus when these electrons are no longer there it takes away that shield which is referred to as De-shielding and the shift will show up to the left side (more downfield higher chemical shift/ ppm). I hope that helped. Good luck

 

[ridethecliche]

This belongs in the question and answer section.
Here's how I learned it in lab and was able to memorize it. It might not be the best but makes perfect sense.
So the electrons around the proton create a magnetic field that opposes the applied field during a NMR. Since this reduces the field experienced at the nucleus, the electrons are said to shield the proton. Just imagine electrons like "protecting" the protons it's literally like shielding. However if there is an electron withdrawing group close in proximity then it withdraws electrons. Thus when these electrons are no longer there it takes away that shield which is referred to as De-shielding and the shift will show up to the left side (more downfield higher chemical shift/ ppm). I hope that helped. Good luck

Good explanation.

I'd add that I think of the better shielding where the e- shield the nucleus better like golf. Where if the numbers are lower, then the players are doing better, i.e. the e-'s are doing a better job of shielding the nucleus so the numbers are lower.

 

[monkeyMD]

Awesome. Thanks!

 

[JJMrK]

Moving to study Q&A.

 

[whiteshadodw]

when i first learned this in ochem, i didn't understand it at all. when i took EnM, i finally understood this. you might want to take a look at how magnetic fields work in the physics section.