can h20 be considered lewis base?

[ninojuice]

can H20 be considered a lewis base? what would be required in order for it to act as a base?


is it because oxygen can donate its electron from lone pair, therefore a lewis base?
if what i have stated is true, than how can it act as a lewis acid??

[chrisf]

Water can be considered a Lewis Base. It can be considered Lewis Base because the oxygen contains a pair of electrons that exist in the highest occupied molecular orbital. This pair of electrons can easily be donated, like you said, making it a Lewis Base.

If I remember correctly, the real reason this is so is because of the difference in energy of the lowest unoccupied molecular orbital and highest occupied molecular orbital is pretty small, making the electrons on the oxygen readily available for donation.

It's able to act as a Lewis Acid if there is something in solution that will readily give up a proton. It can receive the proton by donating a pair of electrons (making it act as a Lewis Base.) However, when protonated; the hydronium ion is highly reactive so if something is present that acts as a Lewis Base (in other words, if something with a pair of electrons in HOMO exists in the solution), the proton will be readily donated (making it act as a Lewis Acid.)

[ninojuice]

ah i see...because H30+ will be dissociated right away, h2o can be just considered a lewis acid also.... thank you.