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Topic: Base and nucleophiles  (Read 4971 times)

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Offline nonlinear

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Base and nucleophiles
« on: May 08, 2011, 12:42:40 PM »
What makes a strong base, such as LDA, or TBuO-, non-nucleophilic? I'm still a bit confused about nucleophilicity... I want to be able to recognize non-nucleophilic bases.

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Offline Honclbrif

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Re: Base and nucleophiles
« Reply #1 on: May 08, 2011, 01:13:38 PM »
Whats the main difference between these bases, and nucleophilic bases such as lithium dimethylamide, or methoxide?
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Offline nonlinear

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Re: Base and nucleophiles
« Reply #2 on: May 08, 2011, 05:45:46 PM »
I'm not sure... is it that they're so bulky that their nucleophilicity is decreased?

Offline matt85

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Re: Base and nucleophiles
« Reply #3 on: May 08, 2011, 06:45:48 PM »
I'm not sure... is it that they're so bulky that their nucleophilicity is decreased?

That's correct. LDA has two bulky isopropyl groups (hence the "D" for di-isopropyl in the LDA acronym) and TBuO- has two bulky tert-butyl groups. Due to this steric hindrance, LDA and TBuO- are not very effective as attacking species (nucleophiles.) However, they are very strong bases, as they are highly-electronegative anionic species.

Offline azmanam

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Re: Base and nucleophiles
« Reply #4 on: May 08, 2011, 08:50:58 PM »
this is correct, but tBuO- has only one t-butyl group, not two.
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Offline matt85

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Re: Base and nucleophiles
« Reply #5 on: May 11, 2011, 12:03:10 AM »
this is correct, but tBuO- has only one t-butyl group, not two.

You're right.

 My bad.  :)

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