Enolates!
Today we saw how to increase the nucleophilicity of the alpha-carbon by creating a deprotonated form of an enol called an enolate. Since the enolate has an overall negative charge, it is a stronger nucleophile than the neutral enol. We discussed the necessary strongly reactive nature of the base and mentioned two in particular -- sodium hydride (NaH) and lithium diisopropyl amide (LDA). Both are strong bases and NaH has the added benefit of forming hydrogen gas and bubbling away (preventing the deprotonation from going in reverse). You were left with the task of determining why hydroxide is a bad choice as a base when making enolates.We saw how the concept of induction led to multiple deprotonations in the haloform reaction, giving what appears to be a strangely oxidized product (a carboxylic acid) from a methyl ketone.
We ended up with a discussion on relative acidities, and noted that a hydrogen on a carbon between two carbonyl groups is much more acidic than a hydrogen on a carbon next to a single carbonyl.
Remember, Friday is a big day -- we will talk about material in Chapter 22.8. The big topics are the Malonic Ester Synthesis and the Acetoacetic Ester Synthesis.
posted by DCChem @ 3:43 PM
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