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
Why is the addition of of ammonia to a haloalkane a problem forming primary amines
Low yield of primary amines due to it bonding with other haloalkanes
how do you form a nitrile from a halo alkane?
Nucleophilic substation of a cyanide ion
Ethanolic and aqueous conditions
How do you form an amine from a nitrile
Nucleophilic addition (reduction)
H2 and Nickel catalyst
or
LiAlH4 reducing agent
Why is synthesis from nitriles a better method for producing amines then synthesis straight from a haloalkane?
Form directly haloalkanes: Low yield of primary amines due to primary amines reacting further to produce secondary tertiary and quaternary ammonium slats
From nitrates only the primary amine can form so yield is massively higher
What conditions are need for nitrobenzene from benzene
Concentration H2SO4 and HNO3 to form the NO2+ ion for electrophilic attack
How do you form an ammonium salt from nitrobenzene
What conditions are needed?
Reduction using Tin/HCL —-> forms an ammonium salt
Room temperatures
add NaOH to the intermediate salt to release the phenylsmime
Under Reflux
What is the Equation for the reaction of nitrobenzene —> Phenylamine
What the conditions?
Explain the reaction
Nitrobenzene is refluxed with tin catalyst and Hcl
A salt is formed
add NaOH to the salt to release the phenylamine
What mechanism is used for forming amides from acyl chlorides and amines
Nucleophilic Addition elimination
Draw the mechanism for the reaction of etanoyl chloride with ethanamide
Which industries/ products are amines used?
Dyes, Nylon, Drugs, Synthesis of new molecules
What are cationic surfactants
Quaternary ammonium slats with a cation that is charged at one end, and non-polar at the other end
How to cationic surfactants work in conditioners
Negative charges on the surface of the hair or fabric are attracted to the cation
This removes the negative charge from the surface and prevents static electricity build up to keep there fabric flat and smooth
How do cationic surfactants sit when placed in water
Charged end in the water and the non polar end repelled (out of the water)
Why is KCN used rather HCN in the production of a hydroxy nitrile
1) HCN is a gas which is hard to store
2) Reacts to produce dangerous byproducts
The strength of an amines basic action depends on what?
The availability of the lone pair being donated on the nitrogen atom
1,6 Diaminohexane is made from 1,6dibromohexane
Name the Reagents, conditions, and Give an equation for the reaction.
Excess Ammonia
Ethanoic, Heat within Sealed Container
Name the reducing against used to reduce nitriles into amines.
H2 with Nickel Catalyst
