amines, amides and aniline
DESCRIPTION
AMINES, AMIDES and ANILINE. Amines. An amine is a base as well as a nucleophile. Some amines are heterocyclic compounds (or heterocycles). Most drugs, vitamins, and many other natural products are heterocycles. A natural product is a compound synthesized by a plant - PowerPoint PPT PresentationTRANSCRIPT
AMINES, AMIDES and AMINES, AMIDES and ANILINEANILINE
Amines
• An amine is a base as well as a nucleophile
• Some amines are heterocyclic compounds (or heterocycles)
• Most drugs, vitamins, and many other natural products are heterocycles
• A natural product is a compound synthesized by a plant or an animal
H N H
H
R N H
H
R N H
R
R N R
R
Ammonia Primary (1o) Amine
Secondary (2o) Amine Tertiary (3o) Amine
Organic bases are amines
Amines are derivatives of ammonia
N 1s2, 2s2 2p1 2p1 2p1----------- lone pair occupies an sp3 orbital
NH2
H Cl
N
H
H
H Cl
Base + Acid = Ammonium Salt
Amines are bases because of the lone pair on the Amines are bases because of the lone pair on the nitrogen atom -nitrogen atom - red litmus paper to bluered litmus paper to blue
O
O HO
OHN(CH2CH3)3
O
OO
O
HN(CH2CH3)3
+ 2 +2
oxalic acid triethylaminetriethylaminium oxalate
The lone-pair electrons on nitrogen allows an amine to turn “inside out” rapidly at room temperature
H2NNH2
Putrescine(found in decaying meat) NH2
Amphetamine(dangerous stimulant)
N
H Piperidine
N
Triethylamine NH2
Isopropylamine
1,4-butanediamine
Some Common Amines
Both upper amines are 1o
This amine is are 2o This amine is 3o
This amine is 1o
NH2 N NNaNO2, HCl
benzenediazonium chloride
+Cl-
0 C
Aniline can be converted into useful diazonium salt
N N
N N
Nuc+Cl- Nuc-
-
Relative Reactivity of Amine
The leaving group of a protonated amine cannotdissociate to form a carbocation or be replaced by ahalide ion
RCH2F > RCH2OH ~ RCH2OCH3 > RCH2NH2
most reactive least reactive
HF H2O RCH2OH NH3
pKa = 3.2 pKa = 15.7 pKa = 15.5 pKa = 36
Reactions of Amines
nucleophilic substitution reactions
CH3CH2Br + CH3NH2
Br
CH3CH2NHCH3 + HBrCH3CH2NH2CH3
nucleophilic acyl substitution reactions
CH3CH2
C
O
ClCH3NH2+ 2
CH3CH2
C
O
NHCH3
+ CH3NH3Cl
Oxidation of Amines
R NH2 R NH OH R N O R N+
O-
Ooxd oxd oxd
R NH
R
+ H2O2 R N+
R
OH
H + OH- R N
R
OH
+ H2O
R N
R
+ H2O2 R N+
R
OH
R + OH- R N
R
O_
+ H2O
R R
a hydroxylamine a nitroso compound
Nitrite Ion, Nitrous Acid, and Nitrosyl Nitrite Ion, Nitrous Acid, and Nitrosyl CationCation
HH++
––OO••••••••
••••NN OO
•••• ••••••••
OO•••• ••••
NN OO•••• ••••
••••HH
HH++
OO••••NN OO
•••• ••••
HH
HH
++••••++
••••NN OO
•••• ••••++OO ••••
HH
HH
••••
ExampleExample
(CH(CH33))22NNHH•••• NaNONaNO22, HCl, HCl
HH22OO(88-90%)(88-90%)
••••(CH(CH33))22NN
••••NN OO
•••• ••••
CH3NH2+HNO2 CH3OH+N2+H2O
Nitrosation of Secondary AlkylaminesNitrosation of Secondary Alkylamines
++••••NN OO
•••• ••••••••NN
HH
++
NN••••NN OO
•••• ••••++
HH++
HH
++
NN••••NN OO
•••• •••••••• nitrosation of nitrosation of secondary amines secondary amines gives an gives an NN-nitroso -nitroso amineamine
Nitrosation of Primary ArylaminesNitrosation of Primary Arylamines
gives aryl diazonium ionsgives aryl diazonium ions
aryl diazonium ions are much more stable aryl diazonium ions are much more stable thanthanalkyl diazonium ionsalkyl diazonium ions
most aryl diazonium ions are stable under the most aryl diazonium ions are stable under the conditions of their formation (0-10°C) conditions of their formation (0-10°C)
ArArNN NN++
RRNN NN++ fastfast
slowslow
RR++ ++ NN22
ArAr++ ++ NN22
Example:Example: (CH(CH33))22CHCH NNHH22
NaNONaNO22, H, H22SOSO44
HH22O, 0-5°CO, 0-5°C (CH(CH33))22CHCH NN NN
++HSOHSO44
––
Transformations of Aryl Diazonium SaltsTransformations of Aryl Diazonium Salts
ArAr NN NN++
ArAr HH
ArAr OOHH
ArAr II
ArAr FF
ArAr BrBrArAr ClCl
ArAr CNCN
Azo CouplingAzo Coupling
Diazonium salts are weak electrophiles.Diazonium salts are weak electrophiles.React with strongly activated aromatic React with strongly activated aromatic compounds by electrophilic aromatic compounds by electrophilic aromatic substitution.substitution.
ArAr NN NN++
Ar'Ar' HH++ ArAr NN NN Ar'Ar'
an azo compoundan azo compound
Ar'Ar' must bear a strongly electron-releasing group must bear a strongly electron-releasing group such as OH, OR, or NR such as OH, OR, or NR22..
ExampleExample OHOH
++ CC66HH55NN NN++ OHOH
NN NCNC66HH55
ClCl––
NC R
R'
O
NC R
R'
O
Amides
Features of a Peptide Bond
1. Usually inert2. Planar to allow delocalisation3. Restricted Rotation about the amide bond4. Rotation of Groups (R and R’) attached to the
amide bond is relatively free
------------- Not acids or bases