Chapter 18 Flashcards
What is an Enolate? What about it’s resonance form?
A ketone with its double bond moved to the alpha carbon, the O is now negatively charged.
Resonance form: Ketone with missing alpha H, that alpha carbon is now negatively charged.
What is an Enol?
A ketone with its double bond moved to an alpha carbon, the =O turns into an -OH
How do you convert a Ketone to an Enolate or an Enol? Describe the final product.
The addition of an LDA to a Ketone results in an Enolate which can then be protonated to an Enol.
The addition of an H3O to a Ketone results in an Enol that conjugates back to a racemic ketone (if the starting ketone has a chirality center)
Describe the process of halogenation of a ketone.
The addition of a halogen + acid or base has the halogen replace an ALPHA hydrogen.
Describe the Haloform reaction.
The repeated addition of an X2 + OH- to a ketone, resulting in the alpha hydrogens of the CH3 being replaced by 3 halogens. The OH- then replaces the CX3 with an O-, and a CHX3 (haloform) is created.
Give the reaction that results in the formation of LDA (Lithium diisopropylamine)
Alkyl Lithium (R-Li) + Diisopropylamine -> Alkyl (R-H) + LDA
Compare the preparation (in terms of substituted H) of Enolates with the use of LDA vs an aqueous acid or base
LDA will remove the less hindered H, Aqueous acids or bases will removed the more substituted H
Describe the process of Alkylation of Ketones (addition of an -R)
- The addition of LDA to form an enolate. 2. The addition of RX to ultimately substitute R for where the H left. The end result is therefore a ketone.
Describe the process of Alkylation of Ketones with an Electrophile.
- The addition of LDA to form an enolate 2. The addition of an Electrophile (+) to ultimately substitute for where the H left. The end result is therefore a ketone.
What is a Beta-Dicarbonyl compound and how does it apply?
A beta-dicarbonyl compound is a compound that has the general formula C=O - C - C=O. It is acidic enough that LDA is not needed.
Describe the Synthesis of Methyl Ketones from a beta-dicarbonyl ester (Acetoacetic) (R-(C=O)-C-(C=O)-O-R)
- The addition of a weak base (EtO(-) Na(+)) to steal the center alpha hydrogen and create an anion.
- The addition of an R-X to replace the alpha hydrogen with an R.
- The addition of a stronger more hindered base (tBuO(-)K(+)or NaOEt) to steal another alpha hydrogen.
- The addition again of another R-X to replace the other alpha hydrogen with an R.
Describe the synthesis of monosubstituted methyl ketone from a beta dicarbonyl ester.
- The addition of a weak base (EtO(-) Na(+)) to steal the center alpha hydrogen and create an anion. 2. The addition of an R-X to replace that lost hydrogen with an R group.
- The addition of 1NaOH, 2H3O+ to create a carboxylic acid from the -OR of the dicarboyl ester and subsequently remove that carboxylic acid group through the use of heat and (-CO2)
(Ultimately this step removed the Ester part of the compound)
Describe the synthesis of disubstituted methyl ketones from a beta dicarbonyl ester.
- The addition of a weak base (EtO(-) Na(+)) and a RX to replace the center alpha hydrogen with an R group.
- The addition of a stronger more hindered base (tBuO(-)K(+) or NaOEt) and another RX to replace another center alpha hydrogen with an R group
- The addition of 1. NaOH 2. H3O+ 3. Heat/(-CO2) to remove the Ester part of the compound.
What happens when there are two ester parts of a compound that need to be removed via the addition of 1. NaOH 2. H3O+ 3. Heat/(-CO2)?
Only one of them is removed. Ends up being a carboxylic acid
When a molecule that has at least one carboxylic acid group is subjected to acid and heat, what happens?
Carboxylic acid leaves as COOH
