Editing Lewis acids and bases (section)

=== Comparison with Brønsted–Lowry theory ===
A Lewis base is often a Brønsted–Lowry base as it can donate a pair of electrons to H<sup>+</sup>;<ref name="hydron"/> the proton is a Lewis acid as it can accept a pair of electrons. The conjugate base of a Brønsted–Lowry acid is also a Lewis base as [[deprotonation|loss of H<sup>+</sup>]] from the acid leaves those electrons which were used for the A—H bond as a lone pair on the conjugate base. However, a Lewis base can be very difficult to [[protonation|protonate]], yet still react with a Lewis acid. For example, [[carbon monoxide]] is a very weak Brønsted–Lowry base but it forms a strong adduct with BF<sub>3</sub>.

In another comparison of Lewis and Brønsted–Lowry acidity by Brown and Kanner,<ref>{{cite journal |doi=10.1021/ja00957a023 |title=Preparation and Reactions of 2,6-Di-t-butylpyridine and Related Hindered Bases. A Case of Steric Hindrance toward the Proton |year=1966 |last1=Brown |first1=Herbert C. |last2=Kanner |first2=Bernard |journal=Journal of the American Chemical Society |volume=88 |issue=5 |pages=986–992 |bibcode=1966JAChS..88..986B }}</ref> [[2,6-Di-tert-butylpyridine|2,6-Di-''tert''-butylpyridine]] reacts to form the hydrochloride salt with HCl but does not react with BF<sub>3</sub>. This example demonstrates that steric factors, in addition to electron configuration factors, play a role in determining the strength of the interaction between the bulky di-''t''-butylpyridine and tiny proton.