If friend agree that ammonia is a Lewis base (electron pair donor) and that this is an Lewis acid-base reaction, (donor-acceptor interaction) climate water is a Lewis mountain (electron pair acceptor), by an interpretation and the truth that there is a reaction. Now, identifying the mechanism of mountain or the acidic website is much more complicated, but you can"t argue the it is acidic, through definition.
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Strictly speaking, a Lewis acid is miscellaneous that develops a shortcut by accepting an electron pair kind another molecule (Lewis base). Water thus does not execute that, quite it is a hydrogen ion from the water that does so. As soon as ammonia acts together a proton agree in water, the Lewis theory calls that a displacement reaction wherein the acid, $\ceH+$, is initially an unified with one basic ($\ceOH-$) and ends up linked with one more base ($\ceNH3$).
I have finally uncovered a satisfactory answer to your question after much research. Jensen (1978) provides fantastic review that the Lewis acid-base theory and also p. 4 of the article provides the answer the you seek$^1$. I shall quote indigenous that page the relevant insights:
So rapid and also striking were plenty of of these neutralizations the Lewis walk on to propose that that default 1 (i.e., quick kinetics) to be the salient attribute of acid-base behavior, arguing further that a fundamental subdivision the acids and also bases be made top top this basis...
Lewis classified those acids and bases which underwent acid-base reaction which proved "essentially zero activation energy" as primary, while those which had actually measurable activation energies to be termed secondary. That further damaged down this secondary course into two varieties (ref 1, p. 4):
The first of these affiliated species, such together $\ce CO2$, in which the sluggish kinetic behavior was apparently due to the need of the types undergoing some sort of internal activation before its primary acid or basic properties came to be apparent.
The 2nd class associated those species in i m sorry the finite activation power wasdue come the break of one or much more auxiliary bonds upon neutralization, resulting in the early $\ce AB$ complex to dissociate into several smaller sized fragments. Hence, Bronsted acids favor $\ce HCl$ and also $\ce HNO3$ were still acids, though currently of the secondary variety, and their neutralizations can be assumed of as originally resulting in an turbulent hydrogen-bridged adduct which then underwent additional decomposition.
To clarify, the Lewis acid-base reaction defined by Lewis is together such:
$\ce A + :B -> AB$
Back to your question... Essentially, $\ce H2O$ deserve to be viewed as the 2nd class of secondary acids suggest by Lewis. During a reaction through Lewis basic $\ce :B$, there is basically some sort of facility formed, that looks choose this $\ce $. The dotted lines show partial covalent bonds. This complicated can be viewed as sort the a "transition state". However, note that this was not in the initial formulation of Lewis. The image below shows the reaction in between pyridine and also $\ce HCl$ regarded from Lewis" perspective. Lewis referred to as this facility an "unstable adduct".
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Based top top the above, we can say that acids of the type $\ce HA$ (where $\ce A$ is one electronegative atom or group of atoms) are second Lewis acids, which take part in acid-base reactions through simultaneous bond breaking of auxiliary bonds. This is because the idea of complexation to type an adduct is quiet present.