Amides Flashcards
Why are amides very unreactive ?
- DO NOT react with water, alcohols, carboxylate ions, halide ions
• Incoming nucleophile is a weaker base than the leaving group
Why are amides more stable than esters and are they more or less reactive ?
- lone pair on N is stabilised by resonance
- amides are less reactive than esters due to stabilisation
What are 1°, 2º, 3° amides?
1° has to 2h’s
2ºhas 1H
3°has no H
what is the “double whammy” effect in amides?
- amides exhibit both hydrogen bonding and strong dipole-dipole interactions
(between N and O) - contributing to higher boiling points.
how many electrons are shared in an amide’s π orbitals?
- an amide has 4 electrons shared between 3 π orbitals.
what is the hybridization of nitrogen in an amide?
- nitrogen is sp² hybridized
- planar, 120
what is rotation around the amide bond like ?
- restricted allows cis and trans orientations
In which solvent is the rate of rotation fastest?
- the rate of rotation is fastest in cyclohexane
- least polar solvent.
how do solvents like water and DMSO interact with organic molecules?
- possess strong dipole moments
- interact with organic molecules through charges and dipoles.
why does cyclohexane facilitate faster rotation?
- cyclohexane has no dipole moment, leading to less interaction with organic molecules and faster rotation.
What is a common method for synthesizing amides from carboxylic acids?
- reaction can be facilitated by using coupling agents like DCC (dicyclohexylcarbodiimide).
what are 5 methods for synthesizing amides ?
- Carboxylic Acid + Amine
- Acyl Chloride + Amine
- Acid Anhydride + Amine
- Ester + Amine
- nitrile + H20
Acid hydrolysis of amines ? (4)
- produces RCOOH + NH4+ (ammonium ion)
- protonation of carbonyl oxygen
- water acts as nucleophile
- reversible reaction
what is the dehydration of amides + what agents are used ?
- amides can be dehydrated to form nitriles
- by heating with dehydrating agents (e.g., POCl₃ SOCl2, P2O5)
What is the general reaction for dehydrating an amide to a nitrile?
RCONH2 ——–> RCN+H20
what happens when amides are reduced by lithium aluminum hydride (LiAlH₄)?
- amides are reduced to amines
How do lactams behave during reduction with LiAlH₄?
- lactams are reduced to form cyclic amines.
what transformation occurs to the carbonyl group in amides during reduction?
- the C=O group is reduced to a CH₂ group, forming an amine.
What is the pH of amides?
- neutral pH
What is the share of e- like in an amide ?
- unequal share of electrons
- greater e density on oxygen
What determines whether a carboxylic acid reacts with an amine to form a salt or an amide?
- salt formation under mild conditions
- RCOOH + R’NH2 —> RCOO- + R’NH3
- using dehydrating coupling reagent like DCC produces amide
Base hydrolysis of amines ?
- OH- is nucleophile
- produces RCOO- + NH3
- irreversible due to resonance stabilisation of RCOO-
