[pcleary]

Mod edit: img tags added. Please use img tags like this: [img]http://image uri[/img] or upload images as attachments (click the "Additional Options..." tab below the edit field in the reply window) or use SMILES code - please do not link to external image hosting websites. For more information on formatting posts correctly, click here. Dan

[magician4]

ref.: why doesn't OR^- attack AlH₂⁺ ?

because there is no such species as AlH₂⁺ involved

ref.: why did the AlH₃ (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⁺  Al³⁺ + 4 ROH

[pcleary]

Thank you for your explanation. I think I am just too useless at organic chemistry to understand (I'm sure that's as simple as you can explain it). I study but it doesn't make sense to me. I always feel like it's an educated guessing game.

Anyways would you be able to explain why this book showed the mechanism like this (screenshot of mechanism explanation in book)?



Mod edit: img tags added. Please use img tags like this: [img]http://image uri[/img] or upload images as attachments (click the "Additional Options..." tab below the edit field in the reply window) or use SMILES code - please do not link to external image hosting websites. For more information on formatting posts correctly, click here. Dan

[orgopete]

Thank you for your explanation. I think I am just too useless at organic chemistry to understand (I'm sure that's as simple as you can explain it). I study but it doesn't make sense to me. I always feel like it's an educated guessing game.

I am doubtful of this, however incomplete or incorrect explanations can confuse anyone. I am of the opinion that our brains are pattern matching machines. Hence, education or teaching an old dog a new trick requires consistency. You want your dog to connect the command to sit with the proper action and the reward. In my class, I emphasize simple patterns and make every effort to repeat them and use them consistently.

Remember, chemical knowledge has evolved by some people being able to pick up patterns even when none was readily apparent. If we advance to today classes, professors fail to recognize how poor explanations or errors may frustrate those less able to deduce the obscure on their own. Maybe some students can, but many cannot. If your professor chose this book and gave no further explanation, then ...

Anyways would you be able to explain why this book showed the mechanism like this (screenshot of mechanism explanation in book)?

No

[magician4]

Anyways would you be able to explain why this book showed the mechanism like this (screenshot of mechanism explanation in book)?
http://imgur.com/nKEESIs

me neither
never heard of any mechanistic studies ref. reduction with LiAlH₄ involving those species shown there...


regards

Ingo