Question #4c4c7

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Truong-Son N.
Oct 25, 2017

Basic activity and nucleophilic activity differ in the sense that the former is thermodynamic and the latter is kinetic.

If something is a good base, it is said to form a stable bond by donation of an electron pair. If something is a good nucleophile, it is said to react quickly (it may or may not form a stable bond but it usually does).

As an example, consider ethoxide:

#"H"_3"C"-"CH"_2-"O"^(-)#

It has very little steric bulk, so it is a good nucleophile (it's fast) but OK base (not large #"pK"_a#). Now consider tert-butoxide:

#("H"_3"C")_3-"C"-"O"^(-)#

This has a lot of steric bulk, so it is a bad nucleophile (it's slow and clumsy) but great base (large #"pK"_a# due to many electron-donating groups on the central carbon).

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