Which anion is more basic in nature?? Explain with reason... NH2- OR Cl-?  As a result, which is more reactive, amides or acid chlorides?

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ncchemist eNotes educator| Certified Educator

The amide anion (NH2-) is much, much more basic than the chloride anion (Cl-).  This is because of their conjugate acids.  Strong acids have weak conjugate bases and weak acids have stronger conjugate bases.  The conjugate acid of Cl- is HCl, a very strong acid called hydrochloric acid.  Since HCl is a strong acid and ionizes completely in water, Cl- is a very weak base.  The conjugate acid of NH2- is NH3, called ammonia.  Ammonia is actually itself a weak base, so its conjugate base NH2- is an incredibly strong base so it can get an extra proton to regenerate NH3 which is much more stable.

As a result of the relative basicity of NH2- and Cl-, we can determine that acid chlorides are much more reactive than amides.  Acid chlorides will react with any number of nucleophiles to undergo displacement and lose a Cl- group.  Amides, however, are very stable and will not react even under harsh conditions with nucleophiles to produce amide anions (NH2-).

So summarize, NH2- is a much stronger base than Cl-, and acid chlorides are much more reactive than amides.

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