Organic chemistry chapter 19

How are amines classified? (i.e. primary, quaternary)

by how many carbons they are attached to (1 is primary, 4 is quaternary, etc.)
How are amines classified? (i.e. primary to quaternary)
By how many carbons they are bonded to (1 carbon to 4, where the 4 bonded has a formal +1 charge)
3 membered cyclic with one nitrogen =?
aziridine
5 membered cyclic diene with 1 nitrogen =
pyrrole
5 membered cyclic ring with one nitrogen =?
pyrrolidine
5 membered ring with a methy attached to the nitrogen?
1 (or N) methylpyrrolidine
5 membered cyclic diene with 2 nitrogens = ?
imidazole
benzene attached to a 5 membered cyclic diene with 1 nitrogen = ?

indole

A Benzene ring with a nitrogen replacing one carbon =?
Pyridine

6 membered cyclic with one nitrogen =?

piperidine

benzene with one nitrogen instead of carbon=?

Pyridine

benzene with 2 nitrogens meta to eachother (not substituents, but replacements for carbon) =?

Pyramidine
Pyramidine attached to imidazole=?
purine
Why can’t enantiomers be isolated around nitrogens?

Inversion can occur due to the lone pair of electrons

What kind of amine(s) can have chirality?
a quaternary amine (bonded to 4 carbons) and amines that are restricted in their rotation (i.e. are part of rings)

N-H vs O-H bonds?

Less polar, meaning less hydrogen bonding, meaning a lower boiling point
What amines are soluble in water?
small amines (i.e. attached to a carbon group of less than 6 carbons)
What do amines smell like?
rotting fish (yum)
How do you increase the solubility of an amine?

Branching

Aqueous amines are ? in nature (pH wise) because ?

Basic; they have a lone pair that accepts protons
pKb of ammonia?
4.74
alkyl amines are (more/less) basic than ammonia
More
What do alkyl groups do to amines? (electron wise and charge wise)
They are electron donating, allowing the cation to be more stabilized.

What is the effect of resonance on amines?

it weakens their basicity, because the electron pair is delocalized.

Aromatic amines are far less ? (pH wise) because ?

basic; the addition of;a proton would make it non-aromatic, decreasing its stability
What is the effect of Hybridization on amines? (pH wise)
Hybridization towards more S character makes amines less basic.

3 main characteristics of Amine Salts

High melting points, very soluble in water, and no fishy odor

What are;3 main reasons for making amines into salts when they are used medically or stored?
They no longer have a fishy smell, the amine salt does not have nucleophilic reactions, and it becomes water soluble.
Explain the process of purifying amines
An amine with other organic compounds is stored in ether over water.; HCl is added to create an amine salt, and the aqueous layer is isolated and added to pure ether.; The aqueous layer is then treated with NaOH, causing the amine to no longer be a salt, and become soluble in the ether layer instead.
What useful process is done with tetrabutylammonium? Bu4N+Cl- and explain the process

Phase transfer is done, Bu4N+ as the catalyst, meaning that in it’s initial form, the Bu4N+ is water soluble, and will react with something in the water phase that makes it ether soluble.  It then moves to the ether and reacts with something there and becomes water soluble again, and repeats the process until the reaction is complete.  The reaction still needs to be stirred thoroughly.

Properties of amines in IR Spectroscopy

N-H stretch between 3200 and 3500. 2 peaks occur for primary amines, one occurs for secondary amines.
What are the 2 resonance forms of the iminium ion?
[image]
Where is the iminium ion usually formed?
During Mass spectroscopy
What is visible of an amine on an NMR spectra? and what can it also mean?
A little hump, that can also be an alcohol. (IR can help or prior knowledge can identify whether it is an amine or not.)

Amines and ammonia react with ? to form ?

Carbonyls; imines
NH2 is a ? (in terms of activation) and is ? directing and may form ?
VERY strong activator; ortho and para; trisubstituents with excess reagent.

What does H+ change in activating amine groups?

It transforms them into a strong deactivator, causing meta direction.
what may happen if you attempt to nitrate an aniline?
it may explode

properties of electrophilic subsitution in Pyridine

N strongly deactivates pyridine and causes substitution in the 3-position.  Electrons in N can react with the electrophile.  If the N attracts a proton, it becomes even more deactivating.

What does the N in pyridine activate?

Nucleophilic substitution

How do nucleophiles react with Pyridine?

they replace good leaving groups in the 2 or 4 positions

By what mechanism do amines react with alkyl halides and what products form?

Sn2 forming mono di and tri alkylated products

How does one form primary amines easily?

Reaction of an alkylhalide with a large excess of ammonia.  R-X + NH3 (excess) –> R-NH2 + NH4+X-
Explain the Acylation of amines by acid chlorides, and why it is useful
Amines attach C=O, causing the chloride ion to leave.  The product is a neutral amide.  It is useful because it decreases the activity of aniline toward electrophilic aromatic substitution due to the fact that even though the elecron pair can cause resonance to help with electrophilic substitution, it can also resonate with the C=O.
How are sulfonamides formed?

primary or secondary amines react with sulfonyl chloride.

Explain the mechanism for hofmann elimination
A quaternary ammonium salt formed from exhaustive methylation (R-NH2 + 3CH3-I –> R-N+(CH3)3 I-) has a good leaving group (the N+(CH3)3). react with 1/2Ag2O and water to form the hydroxide salt, and then heat to be left with the least substituted alkene.
What is the only way to have the E2 necessary for the last step of a a hofmann reaction?

the C2-C3 bond would need the N+(CH3)3 to be trans to the C1.  A C1-C2 bond is stable no matter what (there is no subsituent that needs to be trans to the nitrogen)

A hofman product is always the ? substituted product.
Least
What special property is unusual and unique in amines?
it is easily oxidized even in the air
What are common oxidizing agents for amines?
H202 and MCPBA
What do primary amines oxidize to?

nito compounds bia hydroxyl amine nitroso groups

what do secondary amines oxidize to?
Hydroxylamines
what do tertiary amines oxidize? to

amine-oxides

How are Hofmann and Cope elimination different or similar?

The least subsituted alkene forms, but under milder conditions than that of a hofmann reaction.

What does it mean when a reagent is formed "in situ" and give an example of its occurance

it means 2 or more things that are not the reactant are combined in solution to create the reactant.  Ex. Nitrous acid via nitrite with HCl, which is then protonated to form water and the nitrosonium ion
How do the differnt degree amines react with nitrous acid?

Pirmary amines form diazonium salts, and the secondary amines for N-nitrosoamines (cancerous)

In what temperature range are Arenediazonium salts stable?
0-10 C
Arenediazonium salts are useful because…
the N+ (triple bond) N group is easily replaced, allowing for many new compounds to be formed
Ar-N+(triple bond)N + H30+ = ???

Ar-OH

Ar-N+(triple bond)N + CuCl(Br) =?
Ar-Cl(Br)
Ar-N+(triple bond)N + CuCN=?
ArC(triple bond)N
Ar-N+(triple bond)N + HBF4(KI)=?
Ar-F(I)
Ar-N+(triple bond)N + H3PO2=?
Ar-H
Ar-N+(triple bond)N + H-Ar’=?
Ar-N=N-Ar’

How does one form a primary amine?

Reaction of an aldehyde or a ketone with Hydroxylamine, then reduce the oxime.
How does one form a secondary amine?
react an aldehyde or ketone with a primary amine then reduce the imine.
How does one produce a tertiary amine?
react a secondary amine with an aldehyde or a ketone and reduce the imine salt
How does one form an amide from NH3 or a primary or secondary amine?
by addition of an acyl chloride

How do you turn an amide into an amine? what amines are formed?

the C=O of the amides react with LiAlH4 to form amines +1 to what they were before (Ex. primary becomes secondary, secondary becomes tertiary, etc.)

How does one perform a direct alkylation, and by what mechanism?
By using an extreme excess (10:1) of ammonia with a primary alkyl halide or tosylate.  The mechanism is Sn2 resulting in the alkylamine and amonium halide
Explain gabriel synthesis
phthalimide ion reacts with a primary alkyl halide, and then with H2N-NH2 to form the primary alkyl amine and phthalimide Hydrazide.
What is the structure of the phthalidimide ion?
a benzene with a conjoined 5 membered ring with a nitrogen on the far group, and 2 carbonyl groups to either side.
What is the Azide ion?
N3-
Explain Azide Reduction
Azide reacts with an unhindered primary or secondary halide, or tosylate, then LiAlH4 followed by H2O to form the amine.

Explain nitrile reduction

Primary halide reacts with -C(triple bond)N and is then reduced through H2 or LiAlH4 to form Alkyl(+1 carbon) amine
How is a nitro compound reduced?

Catalytic hydrogenation or active metal in acid.

Explain the hofmann rearrangement of amides
A strong base reacts with an alkyl amide to form alkyl(-1 carbon) amines
x

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