When does LiAlH4 act as a base and when does it act as a nucleophile?

[FROGGBUSTER]

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When you throw in LiAlH4 with a carboxylic acid, you always see the reaction being written out as the Hydride ion attacking the carbonyl function.

But why can't it just de-protonate the OH?

Also, can't LAH also deprotonate alpha carbons of carbonyl functions that are pretty acidic???

Why do we always see it acting as a nucleophile rather than a base when we throw it in with carbonyls? De-protonation is much faster than nucleophilic attack isn't it?

 

[loveoforganic]

 

[FROGGBUSTER]

that helps a lot, but what about de-protonation of the alpha carbons of other carbonyl functions?

 

[loveoforganic]

I think it's due to HSAB theory, but I really don't remember enough about it to explain it