SL - Aldol & Claisen Flashcards
What does the aldol reaction form?
C-C bonds
What do carbonyl compunds form when treated with a base?
Enolate
What is the tautomeric form of carbonyl compounds called?
Enol
What are the 3 steps involved with the base-catalysed aldol reaction?
- OH- deprotonates an alpha hydrogen
- Newly formed enolate attacks an aldehyde via lone pair (carbonyl breaks on attacked molecule)
- Oxygen molecule deprotonates water - reforming OH-
Name a biological example of an aldol reaction
The combination of oxaloacetate and acetyl CoA in the krebs cycle
What are the 4 steps involved with the acid-catalysed aldol reaction?
- Lone pair of electrons on Oxygen reacts with a proton
- (+) Oxygen is unstable, alpha hydrogen removed and new double bond formed- enol
- Enol reacts with a protonated carbonyl and -OH group formed
- H+ is regenerated
What type of elimination occurs in base-catalysed and **acid-catalysed **mechanisms?
Base-catalysed: E1Cb
Acid-catalysed: E1
What is the Claisen Condensation Mechanism?
Formation of C-C bond between two esters
* Occurs using a strong base
What are the 4 steps involved in the Claisen Condensation Mechanism?
- Base deprotonates alpha hydrogen
- The ester anion’s lone pair attacks the carboxyl group of another ester (double bond breaks)
- Double bond reforms as leaving group departs
- Newly formed leaving group deprotonates shared alpha hydrogen (acid needed to mantain final product)
What is the 3 step mechanism of the retro-aldol reaction?
- Base deprotonates -OH group
- Carboxyl formed as C-C bond to adjacent molecule breaks (Forms product 1)
- Protonation occurs of the -CH2 group forming product 2
What is a biological example of the Retro-Aldol reaction?
The cleavage of FBP to GAP and DHAP via aldolase (glycolysis)
Where are a combination of aldol and claisen reactions used in biochemistry?
Terpene Biosynthesis
