Reactions Of Amines Flashcards
What can amines act as?
Base
Ligand
Nucleophile
What is a base?
A proton(H+) acceptor
Why do amines act as a good base?
They accept hydrogen easily
Amines lone pair of electrons allow a proton (H+)’s empty orbital to overlap and form a dative covalent bond
What is formed when amines accept a H+ (and act as a base)
An ion is formed [alkylammonium ion]+
This acts as the conjugate acid, donates the datively bonded hydrogen
Trend for conjugate acid
As alkyl chain increases of amine the pKa of weak acid gets bigger
So aka of acid gets smaller= dissociates and donates H+ less so is a weaker acid
Trend for alkyl length of amine acting as a base
Dissociates into weak acid less as alkyl chain increases so amine acts as a stronger base and is better at attracting H+ as length increases
Why is there a trend for increasing alkyl chain length = weaker conjugate acid but stronger base?
Longer alkyl chain = more electrons fed to nitrogen
So increases electron density to accept a proton and increases attraction between proton and electron cloud so harder to be donated
Base (amine) + acid ——>
Alkylammonium Salt
RNH3+Cl-
Alkylammonium salt + base
Amine + water + anion from acid
Reverses acid + amine ——>salt equation
Amine dissociation in water
Forms alkylammonium ions + OH- ions
Amine + water equation, what acts as the acid?
The water, donates a proton to the amine to form an alkylammonium ion and leaves a OH- ion
Why can amines act as a nucleophile?
Have a lone pair of electrons on nitrogen so amines can donate an electron to other molecules
Amine + acyl chloride forms
A secondary amide + HCl
Mechanism for acyl chloride + amine
Addition-elimination
How is amine + acyl chloride an addition-elimination reaction?
A hydrogen is eliminated from the amine so the nitrogen is added to the acyl chloride (bonds to C=O that breaks to C-O) and nitrogen only needs to form 3 bonds not 4
