ref.: why doesn't OR
- attack AlH
2+ ?
because there is no such species as AlH
2+ involved
ref.: why did the AlH
3 (neutral)...
again: no such species as alane involved in the setup
general explanation:
with every hydride leaving , the alcoholate resulting thereof will replace it
hence , you'll always have species of the general formula [Al(H)
4-x(OR)
x]
- , and those are "active" as long as there is at least one hydride left
only in the post - reduction workup you'll destroy the (for example) [Al(OR)
4- with water:
[Al(OR)
4- + 4 H
+ Al
3+ + 4 ROH