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Organic Chemistry 328 SI
Tutor/SI Applications due this Friday (4/7)!!
6 Day Warning for Exam 3
Exam 3 Review 4/10
Content: Chapters 21-24?
Location: Rotunda A
Pie a professor
Event April 12
Voting Tuesday/Fridays at the chemistry club table
Final Exam Review Wednesday 4/26
Location: Ag Engineering (SAE) 100
Claisen condensation Reactions
Mixed Claisen condensation Reactions
Robinson Annulation Reaciton
Identical ketone or aldehyde
Beta-hydroxyl aldehyde or Beta-hydroxyl ketone
Mixed Aldol Reaction
Ketone or Aldehyde
(Synthetically useful reagents or directed reactions)
Intramolecular aldol reactions
cyclic α,β-unsaturated carbonyl compound
*Less angularly strained product will form
Dehydration of Aldol products
NaOH, ∆ (E1cb mechanism)
H3O+ (E1 or E2 mechanism)
α,β-unsaturated carbonyl compound (Enone)
Two Esters (identical)
NaOEt / EtOH
Nucleophilic Substitution (NOT Addition)
Two Esters (different)
(Synthetically useful reagents)
beta-keto esters or beta-diketones
* Intramolecular Claisen reaction
Carbonyl compound (as an enolate) and α,β-unsaturated carbonyl compound (Michael acceptor)
1. NaOEt / EtOH
Conjugate addition product (1,4-addition)
Reaction: Enolate attacks β Carbon to form a new C-C bond. Protonation of the α Carbon
Enamine and α,β-unsaturated carbonyl compound (Enone)
Mix in THF solvent
Robinson Annulation Reaction
Beta-keto ester, an enamine, or a beta-diketones
And an α,β-unsaturated carbonyl compound
NaOEt / EtOH (twice)
Combines Michael reaction with an intramolecular aldol reaction
What is the product?
1. LiAlH4, ether
Aldol Reactions (Carbonyl condensations)
*Aldol: aldehyde + alcohol
Which statement describes an aldol reaction?
A reaction occurring between two carbonyl groups in the presence of a strong base like LDA.
A reaction between two carbonyl carbons where one is converted to an enolate and adds to the electrophilic carbonyl carbon of the other.
A reaction between two carbonyl groups where one is converted to an enolate generates conjugate addition product.
I and II
-OH / H2O
Two ketones, two aldehydes, or one of each (Mixed)
Reagent: -OH, H2O or Alkoxides, H2O
Reaction: Between two carbonyl carbons where one is converted to an enolate and undergoes alpha-substitution, while the other undergoes nucleophilic addition
If we react excess butanal with –OH and H2O, which product forms?
Dehydration of ß-Hydroxy Carbonyl compound with a base follows which mechanism?
Aldol product dehydration
=> Elimination, unimolecular, conjugated base
Reagent: -OH, H2O (∆ sometimes…)
Anionic enolate intermediate (carbanion)
Forms α,β-unsaturated carbonyl compound
AKA: Enone (Alkene + Ketone)
Dehydration with H3O+
Enol is formed and E1 or E2
*Note: Removal of water drives equilibrium to form the dehydration product, why?
 –OH , H2O
 –OH , H2O ∆
II and III
3-Pentanone is heated with an aqueous base, which product forms?
II and IV
Mixed Adol Reactions
When pentanal and propanal are mixed with –OH, H2O, how many products may form?
Mixed Aldol reactions
Also called Crossed aldol reactions
Not synthetically useful when starting material has various alpha carbons because mixture of products form
Synthetically useful reactions:
SMs only has 1 alpha carbon
1 SM has an especially acidic alpha carbon
Y-CH2-Z (Y and Z are COOEt, CHO, COR or CN)
Would this crossed reaction result in a mixture of products? Explain.
Yes, acetone is significantly more acidic, so this enolate is formed selectively.
Yes, since the compounds are added in at the same time, they will form a mixture of products.
No, the diketone is significantly more acidic, so this enolate can be formed selectively.
No, the acetone is significantly more acidic, so this enolate can be formed selectively.
 LDA / THF
Directed Aldol Reactions
 Prepare the enolate of a carbonyl compound with LDA
 Add the second carbonyl compound
This one will act like the electrophile
 –OH / H2O
*How would these reactions compare to Intermolecular reactions?
SM: Dicarbonyl compounds
Product: Cyclic enone
*Note: Less angularly strained product will form
I and III
Only esters with 2 or 3 hydrogen atoms on the alpha carbon
Reagent: 1. NaOEt, EtOH 2. Aqueous Acid
Substitution, NOT Addition
Base promoted the base is used to drive equilibrium to form the ending enolate.
Protonation step to form the beta-keto ester.
Product: Beta-keto ester
 Diethyl carbonate
Two different ester compounds or ester and a ketone
Only 1 alpha carbon
Ketone has the alpha carbon
Product: beta-keto esters or beta-diketones
*Note: Other variations are used to form beta-diesters or beta keto esters
Reactions with ethyl chloroformate
Reactions with diethyl carbonate
An intramolecular Claisen reaction is named what?
III or IV
Intramolecular Claisen reaction
1,6-diesters form 5-membered rings
1,7-diesters form 6-membered rings
Reagent: 1. NaOEth, EthOH 2. Aqueous Acid
Product: beta-keto esters
*Note: Cyclic beta-keto ester can be alkylated and decarboxylated
The α,β-unsaturated carbonyl compound is conjugated
Involves a conjugated (1,4-addition)
Enolate attacks β Carbon to form a new C-C bond
Protonation of the α Carbon
Product: Conjugate addition product
The Stork Reaction
Robinson Annulation involves which reactions?
Michael reaction and a Diekmann reaction
Claisen reaction and an intramolecular aldol reaction
Aldol reaction and a Diekmann reaction
Michael reaction and an intramolecular aldol reaction
Forms a 6 carbon ring
In an aqueous base solution, What product forms?
What is the starting material?
Exam Review Monday – Come prepared!when starting material has various alpha carbons because mixture of products form