Given :
Some compounds :
.
To Find :
Which of the following compounds has the most deshielded protons .
Solution :
Deshielded means nucleus whose chemical shift has been increased due to removal of electron density, magnetic induction, or other effects .
In simple words deshielding means the ability to shift protons .
Now , among Cl , I , Br and H . Cl is the most electron negative .
Therefore , deshielding will be more in .
Hence , this is the required solution .