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Organic chemistry chapter 19
Organic chemistry review for Amines
77
Chemistry
Undergraduate 2
07/21/2008

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Term

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

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

indole

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

6 membered cyclic with one nitrogen =?

Definition
piperidine
Term

benzene with one nitrogen instead of carbon=?

Definition
Pyridine
Term

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

Definition
Pyramidine
Term
Pyramidine attached to imidazole=?
Definition
purine
Term
Why can't enantiomers be isolated around nitrogens?
Definition

Inversion can occur due to the lone pair of electrons

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

N-H vs O-H bonds?

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

Branching

Term

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

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

What is the effect of resonance on amines?

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

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

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

3 main characteristics of Amine Salts

Definition

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

Term
What are 3 main reasons for making amines into salts when they are used medically or stored?
Definition
They no longer have a fishy smell, the amine salt does not have nucleophilic reactions, and it becomes water soluble.
Term
Explain the process of purifying amines
Definition
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.
Term
What useful process is done with tetrabutylammonium? Bu4N+Cl- and explain the process
Definition

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.

Term

Properties of amines in IR Spectroscopy

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

Amines and ammonia react with ? to form ?

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

What does H+ change in activating amine groups?

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

properties of electrophilic subsitution in Pyridine

Definition

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.

Term

What does the N in pyridine activate?

Definition
Nucleophilic substitution
Term

How do nucleophiles react with Pyridine?

Definition
they replace good leaving groups in the 2 or 4 positions
Term

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

Definition
Sn2 forming mono di and tri alkylated products
Term

How does one form primary amines easily?

Definition
Reaction of an alkylhalide with a large excess of ammonia.  R-X + NH3 (excess) --> R-NH2 + NH4+X-
Term
Explain the Acylation of amines by acid chlorides, and why it is useful
Definition
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.
Term
How are sulfonamides formed?
Definition

primary or secondary amines react with sulfonyl chloride.

Term
Explain the mechanism for hofmann elimination
Definition
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.
Term
What is the only way to have the E2 necessary for the last step of a a hofmann reaction?
Definition

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)

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

nito compounds bia hydroxyl amine nitroso groups

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

amine-oxides

Term

How are Hofmann and Cope elimination different or similar?

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

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

Definition
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
Term
How do the differnt degree amines react with nitrous acid?
Definition

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

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

Ar-OH

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

How does one form a primary amine?

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

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

Definition

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.)

Term
How does one perform a direct alkylation, and by what mechanism?
Definition
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
Term
Explain gabriel synthesis
Definition
phthalimide ion reacts with a primary alkyl halide, and then with H2N-NH2 to form the primary alkyl amine and phthalimide Hydrazide.
Term
What is the structure of the phthalidimide ion?
Definition
a benzene with a conjoined 5 membered ring with a nitrogen on the far group, and 2 carbonyl groups to either side.
Term
What is the Azide ion?
Definition
N3-
Term
Explain Azide Reduction
Definition
Azide reacts with an unhindered primary or secondary halide, or tosylate, then LiAlH4 followed by H2O to form the amine.
Term

Explain nitrile reduction

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

Catalytic hydrogenation or active metal in acid.

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