Organic chemistry 3 summary
,chapter 1 aldehydes, ketones,
derivatives
relative reactivity
Reactivity of carbonyl compounds is influenced by:
thermodynamics stability of
reactants: electrophilicity/ nucleophilicity (electron distribution), resonance
transition state and product: steric crowding, charges, strain, resonance, electron
distribution
kinetics botsende deeltjes model: kans op een succesvolle botsing
chance of the nucleophile hitting the carbonyl carbon steric hindrance
Aldehydes are more reactive than ketones
the alpha carbon has more partial positive charge because hydrogen is more electron-
withdrawing than carbon
a hydrogen causes less steric hindrance than a carbonyl group at the carbonyl carbon during:
the approach of the nucleophile kinetics
steric crowding in the transition state, causing it to be less stable thermodynamics
Aldehydes and ketones allow for nucleophilic addition reactions only, because -H and -R are no good
leaving groups (not acidic)
carboxylic acid derivatives however can do nucleophilic addition and substitution reactions
sugar units are held together by acetal linkages
protecting groups
cyclic acetals can serve as protecting groups of ketones in synthesis, and are reversed by hydrolysis
of the formed acetal
, alcohol groups can be protected as silyl ethers by first adding TBDMS chloride, and is regenerated by
adding a certain compound to the TBDMS ether
carboxylic acid groups can be protected as esters by adding alcohols
reactions
Aldehydes, ketones and carboxylic acid derivatives can react with Grignard reagents to form
carbon-carbon bonds at the carboxyl carbon product obtained upon acid workup
formaldehyde + Grignard 1’OH
aldehyde + Grignard 2’OH
ketone + Grignard 3’OH
non-chiral reagents yield a racemic mixture
Aldehydes and ketones react with carbonyl compounds to form a carbonyl group via a new C-C
bond
Aldehydes and ketones react with excess cyanide ions to form cyanohydrins
Aldehydes + NaBH4 1’OH by reduction
Ketones + NaBH4 2’OH by reduction
Esters + 2LiAlH4 split into two alcohols by reduction
Esters + DIBALH aldehydes + alcohol byproduct (uncomplete reduction)
Carboxylic acids + 2LiAlH4 1’OH by reduction
Amides + LiAlH4 amines by reduction (removal of =O group)
whenever you add acid to a reaction that involves nitrogenous compounds, the nitrogen will almost
always get protonated and becomes unreactive
protonated nitrogen is only moderately basic, it is less basic at that point than OH-
addition of trace acid (often denoted HB) , however, will rather protonate the =O group than
the N-group
,chapter 1 aldehydes, ketones,
derivatives
relative reactivity
Reactivity of carbonyl compounds is influenced by:
thermodynamics stability of
reactants: electrophilicity/ nucleophilicity (electron distribution), resonance
transition state and product: steric crowding, charges, strain, resonance, electron
distribution
kinetics botsende deeltjes model: kans op een succesvolle botsing
chance of the nucleophile hitting the carbonyl carbon steric hindrance
Aldehydes are more reactive than ketones
the alpha carbon has more partial positive charge because hydrogen is more electron-
withdrawing than carbon
a hydrogen causes less steric hindrance than a carbonyl group at the carbonyl carbon during:
the approach of the nucleophile kinetics
steric crowding in the transition state, causing it to be less stable thermodynamics
Aldehydes and ketones allow for nucleophilic addition reactions only, because -H and -R are no good
leaving groups (not acidic)
carboxylic acid derivatives however can do nucleophilic addition and substitution reactions
sugar units are held together by acetal linkages
protecting groups
cyclic acetals can serve as protecting groups of ketones in synthesis, and are reversed by hydrolysis
of the formed acetal
, alcohol groups can be protected as silyl ethers by first adding TBDMS chloride, and is regenerated by
adding a certain compound to the TBDMS ether
carboxylic acid groups can be protected as esters by adding alcohols
reactions
Aldehydes, ketones and carboxylic acid derivatives can react with Grignard reagents to form
carbon-carbon bonds at the carboxyl carbon product obtained upon acid workup
formaldehyde + Grignard 1’OH
aldehyde + Grignard 2’OH
ketone + Grignard 3’OH
non-chiral reagents yield a racemic mixture
Aldehydes and ketones react with carbonyl compounds to form a carbonyl group via a new C-C
bond
Aldehydes and ketones react with excess cyanide ions to form cyanohydrins
Aldehydes + NaBH4 1’OH by reduction
Ketones + NaBH4 2’OH by reduction
Esters + 2LiAlH4 split into two alcohols by reduction
Esters + DIBALH aldehydes + alcohol byproduct (uncomplete reduction)
Carboxylic acids + 2LiAlH4 1’OH by reduction
Amides + LiAlH4 amines by reduction (removal of =O group)
whenever you add acid to a reaction that involves nitrogenous compounds, the nitrogen will almost
always get protonated and becomes unreactive
protonated nitrogen is only moderately basic, it is less basic at that point than OH-
addition of trace acid (often denoted HB) , however, will rather protonate the =O group than
the N-group
