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7 Cards in this Set
- Front
- Back
Treatment of an aldehyde or ketone with a Grignard reagent,RMgX,yields....
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an alcohol by nucleophilic addition of a carbon anion, or carbanion
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A carbon-magnesium bond is strongly polarized, so a Grignard reagent reacts for all practical purposes...
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as R:-+MgX
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A grignard rxn begins with....... thereby making the carbonyl group .....
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- an acid-bases complexation of Mg+2 to the carbonyl oxygen atom
- a better leaving electrophile. |
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In the Grignard Rxn's 2nd step is where a Nucleophilic addition of R:- produces a ...
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tetrahedral magnesium alkoxide intermediate, and protonation by addition of water or dilute aqueous acid in a separate step yields the neutral alcohol
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Unlike the nucleophilic addition of water and HCN, Grignard additions are irreversible because . .
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a carbanion is too poor a leaving group to be expelled in a reversal step
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Just as addition of a Grignard reagent to an aldehyde or ketone yields
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- an alcohol, so does addition of hydride ion,:H
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In an addition of a Grignard reagent to an aldehyde or ketone, LiAlH and NaBH4 act as if they were donors of hyride ion in a nucleophilic addition rxn. Addition of water or aqueous acid after the hyride addition step protonates
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the tetrahedral alkoxide intermediate and gives the alcohol product
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