Amines Flashcards
Draw the structures for a primary secondary and tertiary amine and a quarter any ammonium ion.
What is the prefix and suffix for an amine
-Amine
or
amino-
Why are amines so reactive
Lone pair of electrons on the nitrogen means that it is readily available to react with other molecules
What shape are Amines (include bond angles)
Trigonal Pyramid
107 Due to lone pair on N
What kind of intermolecular forces to amines experience?
Hydrogen Bonding due to a very large electronegative difference between N-H & a lone pair causing a permanent dipole so strong it can form attraction between multiple molecules surrounding the mole
&vdw
Do amines have a higher or lower melting point then alcohols?
Lower
Nitrogen has a lower electronegativity then oxygen so the electronegative difference is lower so weaker hydrogen bonding occurs between molecules
At 298K what state are amines in
Short chains are gasses
Longer chains are volatile liquids
What sent do amines have?
Fishy smell - rotting fish
Up to what carbon chain are amines are soluble in a polar solvent and why?
Up to 4 carbons
The polar bonds of N-H make the molecule polar enough to be soluble in polar solvents
After 4 the non-polarity of the hydrocarbon chain make the molecule not polar enough to disolve
What kind of solvents are amines soluble in?
Non-Polar solvents (large chain length) & polar solvents (small chain length)
What is the solubility of Phenylamine
Not very soluble
due to the Non-polarity of the benzene ring not being able to form hydrogen bonds
When can amines act as bases
When they form a ammonium ion (bonded with a H+)
When do amines act as nucleophiles?
Standard molecule
When there’s an electron-deficient carbon that the amine can donate its electron pair two in close proximity
Draw the mechanism for the basic action of an amine with water
What is the product
RNH3+ or NH4+ ammonium ion which can form a salt with an anion
Is an ammonium salt soluble in water?
Yes, it’s ionic and can attract to the polar bonds within water molecules
How do you form an amine from a soluble ammonium salt
add a strong base (NaOH)
Removes the H+ ions from the ammonium ion
For an amine to be a strong base they have to have _________________________
the greatest electron density around the nitrogen atom
Positive inductive effect causes the electron pair to react with other molecules more readily
What is the positive inductive effect?
Positive inductive effect —> pushes electrons towards the nitrogen , to increase electron density of the nitrogen so the lone pair reacts more readily with electrophiles
What effect to alkyl groups have on the electron density of an amine and its base strength?
Increases the positive inductive effect which increases the electron density around the nitrogen atom
This intern makes the amine a stronger base due to the lone pair being donated more readily
What effect to aryl groups (derived from an aromatic ring) have on electron density and bace strength of an amine?
negative inductive effect
-decreases electron density around the Nitrogen
Making it a weaker base as it cannot donate electrons as readily
Why are tertiary amines actually not powerful bases?
They are insoluble in water due to there not being any N-H bonds in the molecule so hydrogen bond cannot form
Place the following molecules in order of bace strength
NH3, Primary Amine , Secondary Amine , Tertiary amine and phenylamine
Strongest
Secondary
tertiary
primary
ammonia
aromatic amines
Weakest
How can primary amines then form Secondary Tertiary amines and Quaternary Ammonium ions?
In excess ammonia
Multiple nucleophilic substitutions starting with a haloalkane
Primary amine acts a nucleophile on the haloalkane
Bonds with the now alkane chain and a hydrogen leaves the molecule by joining an ammonia to form an ammonium ion
this forms a secondary amine
This process repeats but with the secondary amine as the nucleophile and tertiary ion until a quaternary i ammonium. ion is formed
