amines Flashcards
What are amines? What different types are there?
Structures with a Nitrogen. You can have primary, RNH2, secondary R2NH, tertiary R3N, quaternary ammonium salt R4N+ X-/ ammonium ion R4N+
What are heterocyclic amines?
Compounds with a ring, aromatic or not with a nitrogen within the ring
What orbital are the lone pair of electrons on a neutral nitrogen located?
In sp3 orbital
What is a benefit of primary and secondary amines?
They can form hydrogen bonds
What is the relative strength of N-H and O-H bonds?
N-H are weaker than O-H bonds
How does hydrogen bonding affect boiling point of amines?
Hydrogen bonding allows for a higher boiling point than alkanes but still lower than ROH due to relative h bond strength
Are amines basic?
Amines are the most basic of neutral molecules
Are amines acidic?
Not very acidic unless in the presence of a strong base like a gringard
Are ammonium ions basic or acidic?
They are somewhat acidic
How do the number of alkyl groups affect the basicity of amines?
Not entirely sure but increasing number of alkyl groups increases steric hinderance affecting its ability to act as a base but also stabilize the N by being an EDG
Why are alkyl amines more available to form bonds?
They have no resonance so the lone pair on the N is very available for bonding
How does resonance affect the relative basicity of an amine?
Resonance allows for delocalization of N lone pairs and makes them less available to form bonds so it is a weak base
How do EWG and EDG affect amine basicity?
EWG decrease basicity, increase Ka, decrease pka
EDG increase basicity, decease Ka, increase pka
Are amides basic?
No! The lone pair of electrons on the N are less available for bonding since they are tied into the resonance and stabilization of the carbonyl
Why do we not use Sn2 reactions to prepare amines?
Because the N will keep reacting with the R-X and add multiple R to itself and cause a mixture of products. You cannot stop the reaction at any one point
What are the reaction conditions for Gabriel synthesis?
Reactant: potassium phthalimide (Nu) + Counter ion
Conditions: 1) R-X, DMF 2) H2NNH2, ETOH
Product: primary alkyl amine
Reaction conditions for alkyl azide reduction?
Reactant: alkyl azide (R-N3)
Conditions: 1) LAH, ether 2) H2O or H2 Pt
Product: amine (RNH2)
Reaction conditions of alkyl nitrile reduction?
Reactant: alkyl nitrile (R-CN)
Conditions: 1) LAH, ether 2) H2O or H2 Pt
Product: R-CH2NH2 * carbon from C of nitrile remains
Reaction conditions of nitro alkane reduction?
Reactant: nitro alkane (R-NO2)
Conditions: H2, Ni or 1) Fe, HCl 2) NaOH
Product: amine
Reaction conditions of amide reduction? Benefits?
Reactant: amide
Conditions: 1) LAH, ether 2) H2O
Product: primary, secondary, or tertiary amines
Benefit: makes all types of amines
Reaction conditions of reductive amination? What intermediate is formed?
Reactants: aldehyde/ketone
Conditions: NH3 (or amine) | H2, Ni
Product: amine
* imine intermediate is formed
Why do we use H2 and Ni in the reductive amination and not other reductive conditions?
It is not strong enough to reduce the carbonyl but is strong enough to reduce the imine intermediate
Reaction conditions of Hofmann elimination? Why is it unique?
Reactants: amine
Conditions: xs CH3Br | Ag2O, H2O
Product: alkene (anti-zaitsevs rule)
Unique since it uses Hofmann rule (forms less substituted C=C)
What Newman projection confirmation must be used in order to follow Hofmann rule?
Hydrogen and amine group must be anti-coplanar for beta elimination
