Carbonyls 2 Flashcards
What are aldehydes oxidised to?
COOH
What oxidising agents are used?
CrO3
KMnO3
HNO3
What is ethinylestradiol used in?
Formulation of combined pill
What is required in ethinylestradiol?
NaNH2
Liquid NH3
Why do all COOH derivatives react by same mechanism?
Polarity of carbonyl group
What happens in nucleophilic acyl substitution?
Nu- adds carbonyl carbon
= forms tetrahedral anionic intermediate
Leaving group expelled
Tetrahedral intermediate eliminated weakest base
When is Nu- expelled and why?
Nu- weaker than leaving group
= Nu- more stable than L-
When is L- expelled and why?
L- weaker than Nu-
= leaving group more stable than Nu-
Which intermediate will decompose the fastest?
One with best leaving group
What happens to reactivity as leaving group becomes more basic?
Decreases
Why is a WB more electronegative?
Able to accommodate negative charge better
Why is a WB better at inductive e- withdrawal from carbonyl C?
Increases electrophilicity of carbonyl carbon
More electrophilic carbonyl groups = more reactive to addition
Carbonyl carbon more susceptible to nucleophilic attack
Are acid halides more reactive than amides?
YES
Why is chloride good leaving group?
Undergoes acyl substitution easy
Is chloride useful in pharmaceutics?
Too reactive
What do you need to synthesise acid chlorides?
COOH + SOCl2 (thionyl chloride)
What reactions can acid chlorides undergo?
Nucleophilic acyl substitution
Hydrolysis
—-> ester/amides
What happens in nucleophilic substitution of acid chloride?
Follows general mechanism
Halogen replaced by OH, OR, OC(=O)R or NH2
What is formed acid chloride + NH3?
Amide
What is formed acid chloride + R’OH?
Ester
What is formed acid chloride + R’CO2-?
Acid anhydride
What is formed acid chloride + H2O?
Carboxylic acid
What is does acid chloride hydrolysis form?
COOH
What happens in acid chloride hydrolysis?
Add H2O
Tetrahedral intermediate undergoes elimination of Cl- + loss of H+ to give COOH
What is formed acid chloride + alcohol?
Ester
What is formed acid chloride + NH3?
Primary amide
What is formed acid chloride + RNH2?
Secondary amide
What is formed acid chloride + R2NH?
Tertiary amide
What must be present to form ester from acid chloride?
Presences of tertiary amine base
OR
NaOH
What reactions can acid anhydrides undergo?
—-> esters
What does acetic anhydride form?
Acetate ester
Are anhydrides less reactive than acid chlorides?
YES
What reactions can esters undergo?
Transesterification
Aminolysis
Reduction
What happens in transesterification?
Alkoxy group replaced by another with acid or base catalyst
What is required in transesterification?
Large excess of alcohol
What happens in aminolysis?
NH3, primary amine or secondary amine react to form amide
What is the equation for aminolysis?
RCOOEt + NH3 —-> RCONH2 + EtOH
What happens in reduction of esters?
Yields 2x = aldehyde the primary alcohol
What is required in reduction of esters?
LiAlH4
What is Xenical (active orlistat)?
Anti-obesity drug
Where does Xenical work?
Locally in stomach + small intestine
What does Xenical prevent?
Action of gastric + pancreatic lipases
How does Xenical work?
Irreversible acylation of active site serine in phospholipase
Inactive enzyme cannot hydrolyse triglyceride = block fat uptake
What is acetylcholinesterase responsible for?
Nerve-impulse transmission
What is the second site of reactivity for aldehydes, ketones, esters + N,N-disubstituted amides?
Alpha H
= acidic enough to be removed by strong base
In reaction elonate ions + enols what does the reaction at C or O depend on?
Electrophile + reaction conditions
Where does protonation normally occur in reaction of elonate ions + enols?
O site
What is the consequences of enolization?
Stability
Racemization = any chiral centre next to carbonyl prone to racemization
What happens when alpha carbon is halogenated?
Electrophilic