Nh4cl is sometimes preferred instead of hcl or h2so4 for "acid" work-up after grignard reactions, particularly when the expected and desired product is a tertiary alcohol because NH4+ is a much milder acid than HCl or H2SO4, which achieve the protonation of
the oxyanion to yield the alcohol while minimizing the risk of dehydration.
Ammonium chloride (NH4Cl) is the used as reagent that quenches the magnesium alkoxide product of the Grignard addition.
It is a proton source without being acidic as in acidic medium the protonation of the tertiary alcohol product and elimination to the alkene.
In the presence of HCl or any other strong acid protonation proceed and form alkene but not with ammonium chloride.
Thus from above we concluded that Nh4cl is preferred instead of hcl or h2so4 for "acid" work-up after grignard reactions.
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